greymouser7
Vagrant Vagabond “Veni Vidi Vici”
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? They say it has a different case. Is one better/worse?
How would you tell the difference?
I am guessing gears from either can go in between?
Sure grips interchange-able?
What do we want to avoid? I have some of the Data here..any experience?
Shims needed? <-Do they weaken the assembly?
Do you guys have a prefered brand of bearings or parts?
If I want to beat this car up on the back roads how long would a sure grip last??
I know that there are 27 & 29 spline axles-what exactly does that mean & in regards to interchange-ability?
69-96 are 27 spline
97-up are 29 spline <-from web
Back spacing ?
Are 8 1/4" limited slip units are ratio specific? ( 2.25/2/45 or 2.71 & up)
I have a volare road runner Awhatever package 360/727 car's axle, a 74 RR 8 1/4 axle, an 8 1/4 axle assembly from an a body 5 on 4.5 bolt pattern,
I have an F body i would like to run a more narrow axle with for wider tires. It has the 76 RR front suspension on it now and came with a floor shift manual. The car is getting a 360..
art # 542074 - Auburn High Performance Series - 8 1/4 & 8 3/8" Chrysler (2.71-up) -- 29 Spline <-worth it?
http://www.moserengineering.com/dif...-series/8-1-4-chrysler-2-71-up-29-spline.html
Some data so far:
What is a good set of cruise gears?
http://www.forabodiesonly.com/mopar/showthread.php?t=243344
Rear Axles: Chrysler 8 1/4" Rear Axle
« on: January 01, 2008, 21:31:18 »
Chrysler Corporation's Spicer 8.25" rear was one of two differential types used in M-bodies, with the other being the weaker 7.25" unit. The 8.25" rear axle first appeared around 1969 in Plymouth Belvederes, Satellites and Dodge Coronets. The measurement refers to the size of the ring gear. This gear, which is turned by the pinion gear, changes the direction of the power being transmitted to it.
The pinion gear is turned by the driveshaft. From 1973 on, the 8.25" rear was used in virtually every rear wheel drive car model produced by Chrysler through 1989 and in trucks and Jeeps through the 1990s. Some truck versions were designated as 8 3/8" or 8.375", but many internal parts interchanged with the 8.25" unit. It should be noted that all 8.25" rear axle assemblies DO NOT necessarily interchange across all models due to different widths.
Built by the Dana Corporation, the housing is cast iron with tubular steel axle tubes pressed and welded in to form a complete carrier and tube assembly. The gear assembly is accessed by removing an inspection cover having 10 bolts. 8.25" axles use either the "7260" or "7290" style U-joints. All 8.25" rears had 3" axle tubes with large bolt pattern (5 X 4.5" bolt circle) axles. Units with a 2.45:1 gear ratio have a special case that will not accept any other gear ratio. The axles are retained by a c-clip on either side. All axles were 27 spline until 1997 when they were upgraded to 29 spline.
Although the consensus among many Mopar enthusiasts is that a Sure-Grip (limited slip) equiped 8.25" rear is good for up to 500 crank horsepower, it fares much better in street applications than the strip, and in lighter cars than heavy cars. Open 8.25" differentials are more prone to fail at higher horsepower levels than Sure-Grip units. The 8.25" axle has considerable aftermarket support since it was so widely used in the 1970s for performance use.
7.25" To 8.25" M-Body Swap (Originally posted by Malcolm)
If you currently have a 7.25" axle, the 8.25" axle will drop right onto the spring perch pad centers perfectly, requiring no modifications. On early M-body 8.25" rears, the measurement from the outside of the left drum to the outside of the right is one inch narrower than the later M-bodies, but there should be no tire clearance problems. As I mentioned in the old Forum, I run 7 inch rims and 225/70 15's without any problems and there is room for larger tires.
You will need:
It's also a lot safer to do a brake job on everything in the rear while you're at it. It would be smart to replace both the brake lines on the axle and the rear brake hose (from body to axle) while you're there. They're cheap and also easy to get at while the axle's out.
Great time to replace the rear shocks too if money permits. New axle U-bolts and a buddy to help you lift the axles out and in and you're all set.
If you find a 727 equipped 4 door M-body with the driveshaft in it, the front yoke will not fit your 904 transmissions spline. In addition the wagons will have longer drive shafts, which require shortening and re-balancing.
TRW makes a greasable heavy duty U-joint (part # 20124) that takes a beating and is well advised if you're going to spell your name on the highway in twin streaks of rubber (spelling "Malcolm" used to take a while until I installed the 360). Back to the U-joint. The nipple is on the end of one of the caps not in the valley of the inner cross where you can't get a grease gun on. Note: NEAPCO (New England Axle Product Company) also has one with the zerk in one of the caps.
Factory axle dimensions (7.25" and 8.25") for all F/J/M cars:
http://www.hemmings.com/mus/stories/2007/01/01/hmn_feature21.html
Feature Article from Hemmings Muscle Machines
January, 2007 - Jim O'Clair
We have written about plenty of rear-axle conversions for your consideration over the past few years. Earlier articles on Mopar differentials featured the 8 3/4-inch and 9 1/4-inch Chrysler units as well as the Dana 60. Because these three axle possibilities are getting harder to find and cost more, we recommend a less expensive alternative for your Chrysler product--the Chrysler 8 1/4-inch axle. The unit is commonly referred to as the 8 1/4-inch corporate axle. This differential is a Salisbury-type axle, meaning the ring and pinion can be accessed from the rear, as opposed to the Ford 9-inch or Mopar 8 3/4-inch, which are accessed by removing the third member from the front of the differential. Although not as strong as these other two units, they are reasonably easy to locate because Chrysler used them in a wide range of original applications and, secondly, this rear is much lighter than the Mopar 8 3/4-inch, without sacrificing strength.
Used extensively in passenger cars beginning in 1972, the 8 1/4-inch housing also was used in 1971 and newer Dodge B-vans and pickups. This differential is a great candidate for upgrading many Mopar 7 1/4-inch rear ends by adding strength without spending a lot of money. Original passenger car ratios ranged from 2.45:1 to 3.21:1. The truck 8 1/4-inch differentials had additional ratios of 3.55:1 and 3.90:1. A fuel-sipping 2.24:1 ratio was offered in some 1980-'81 passenger car applications, too. Aftermarket suppliers even offer 4.10:1 and 4.56:1 ratios, bigger than original equipment.
Two differential carriers were used in most of these axles. With the exception of the fuel-miser 2.24:1 ratio that we mentioned was used in 1980-'81, any other ratios smaller than 2.71:1 used one carrier and anything above 2.71:1 used a larger carrier. The housing is accessed from a rear cover that is about 11 1/4 inches across by 10 1/4 inches high and has an oval 10-bolt pattern. The pinion on the 8 1/4-inch axle is beefy. It measures 1 5/8 inches in diameter and has 27 splines. The Mopar 8 1/4-inch rear came without a limited-slip differential when it was first offered, however, it was offered in the 8 1/4-inch after 1973. There are also numerous suppliers which offer aftermarket limited-slip units, if an original unit cannot be located.
To determine if a rear axle is equipped with a limited-slip differential while it is still on the vehicle, jack up the rear of the car and place it on jack stands. Put the vehicle in neutral and spin one rear wheel counterclockwise while observing the other wheel. If it spins in the same direction as the wheel you are turning, it is a limited-slip rear. If the other wheel does not spin, you have an open-gear differential. A more obvious clue would be that most Chrysler rears would also still have the Mopar additive tag located on or near the rear cover, specifying the use of part number 4318060 limited-slip additive.
Passenger car (and most truck) axles are 27-spline and have a flange retainer that holds them to the end of the housing. The axle bearings were installed into the axle tubes and C-clips were used to hold the spline of the axle into the differential. This is similar to the Chevrolet, Buick, Olds and Pontiac axles; in fact, the axle bearing for the Chrysler 8 1/4-inch rear is the same for applications with a 2 1/4-inch axle tube (a 2.535-inch was also available). As with Chevrolet rear ends, the axle bearing can be its weakest link. The axle actually acts as the inner race for the rollers in the axle bearing, which can lead to premature wear in the axles themselves. There are repair bearings available which change the contact point on these axles once the bearing contact area on the axle becomes scored, and these repair bearings use an integral oil seal. Replacing the original two-part bearing and seal with this repair bearing assembly alleviates concerns about the strength or reliability of the 8 1/4-inch axles. The CR or BCA part number for the repair bearing is RP-1563-TAV. Performance replacement retainers are available to eliminate the use of the axle c-clips. The pinion yoke accepts a Detroit 7260-style U-joint the Spicer part number is 5-1306X.
Replacement yokes are also available from Spicer; part number 2-4-5851X. Several adapter joints are available to allow you to use the Detroit-style pinion yoke from the donor vehicle and still be able to use your original driveline.
You will most likely find a Chrysler 8 1/4-inch rears under the following cars:
We recommend you thoroughly inspect your donor differential before attempting an installation. Change the fluid and all seals and inspect gear teeth and bearings. If you have located a limited-slip differential, careful inspection of the positraction unit is also important. Should you need to replace any internal bearings, make a notation of the part numbers on them or find out the year the donor differential unit was produced. Bearing packages for the 8 1/4-inch rear are different, depending on if the axle was built before or after 1976. The 8 1/4-inch housing holds two quarts of 85W90 gear oil and, as with all Mopar locking rear ends, limited-slip units require 6 ounces of limited-slip additive.
Although lighter than the Chrysler 8 3/4-inch rear end, the 8 1/4-inch unit is heavier than some of the stock 7 1/4-inch Mopar 9-bolt assemblies it has been known to replace. You can transplant the 8 1/4-inch rear end in many non-Chrysler vehicles, too. Two- and four-wheel-drive pickup differentials will be 65 inches wide, making them compatible with earlier Mopar B-, C- and D-body cars, as well as full-size Chevrolet Blazers. The B-series van rear ends measure about 67 inches, which makes them a prime candidate for swapping into 1970s Ford vans. The 8 1/4-inch rear can be used in many street rod projects as well. C-body passenger car differentials are good candidates for 1935-'41 Ford pickups and 1940-'54 Chevrolet passenger cars. The Durango/Dakota 8 1/4-inch differentials measure 63 inches wide; however, the left axle is longer than the right axle and, as we have already mentioned, the axles are 6-lug. For ease of installation, we would not suggest using the offset Dakota/Durango rear end in earlier cars. But, the 8.25-inch Dakota differentials can be swapped between these two models. Original axle width and spring perch dimensions for most American cars and trucks are available in the parts locator section of our Web site; www.hemmings.com. This list continues to be updated as new information is received from our readers.
We checked with several used parts yards and found open differentials for mid-1970s A-bodies readily available for between $75 and $350. A rear end from a 1981 Diplomat cost between $125 for an open unit and $350 for a 2.94:1 with a limited-slip differential. Be aware that some used limited-slip differential units can sell up to $750. We recommend you first determine how big of a gear you want to run before buying one. If fuel economy is key, you'll want to find one with a 2.71:1 ratio or less. Changing gears later will cost less than $300. If you need a larger ratio for a work truck or heavier vehicle application, you will want to find a unit that has an original ratio of at least 2.94:1, so the carrier will work for any ring and pinion ratio up to 4.56:1. If you need to add a limited-slip differential to an open rear, Trac-Lok carriers for both 27- and 29-spline differentials begin at $250. Replacement parts, such as bearings and seals, can be easily found at a local auto parts store. On many applications, spring perches may need to be moved; however, this can be done easily with a welder. You can move the perches that are on the axle or purchase of a set of replacement spring perches through aftermarket rear-suspension suppliers. You should be able to locate these for less than $40 per pair. But, even with the purchase of a few items to beef-up your 8 1/4-inch donor axle, you are still way ahead of the curve if you consider that aftermarket 8 3/4-inch or 9 1/4-inch differentials sell for $1,200 to $1,500.
This article originally appeared in the January, 2007 issue of Hemmings Muscle Machines.
webwisdom "Sure they built 8 1/4 Sure Grips..Would I advise running one? Nope, not when there's 8 3/4's out there. You WILL break the 8 1/4" rear with a healthy small block, a Big block with destroy one."
webwisdom "Be careful with using later-model axles, too. I once tried swapping in a rear from a Volare into a '63 Valiant. The width was close enough, but it wasn't a bolt-in because A-body leafs have a big pin that sticks up and goes into a hole in the spring perch that locates the axle and keeps it from squirming around on the spring. I don't remember the details, but the Volare rear had some other way of accomplishing the same thing. I was able to locate another rear from an A-body, so I never bothered to solve the problem."
Webwisdom from:
http://forums.moparmusclemagazine.c...rear-end-how-much-is-it-good-for-torque-hors/
drmopar :This is a surprising decent rearend that has been overlooked by most. Just beware when buying
the posi, there are two different units. One for 2.41 and higher gears and one for the others. My brother has a 8 1/4 in his 14 second Duster. No issues. I have also seen them in a 12 second Aspen. The guy ran it this way for yrs. without any issue.
He has a 360 making 450 horse with slicks.
The C-clips on the mopar rear end cannot drop out like a chevy unit, so no need to worry about spitting out an axle.
Good Luck.
68440Barry:
I have an 8.25 posi in my 74 pickup with a 67 440 and about 400 h.p. So far so good.
RBolig
I have a 4.10 geared 8-1/4 in the Dart Sport with a 400 hp small block and a four speed, and it's having no problems.
http://www.dodgecharger.com/forum/index.php?topic=84378.0
http://board.moparts.org/ubbthreads/showflat.php?Number=5610902
http://www.moparmusclemagazine.com/techarticles/drivetrain/5148_custom_rear_end_install/
https://www.allpar.com/forums/topic/87858-8-14-rearend/
Do you think that an 8-1/4 rearend with 3.91 or 4.10 gears and a limited slip would stand up to approximatly 450hp and 400 pound feet of torque from a 360 in regular street use with street tires? or with street slicks?
I'm inclined to believe that such a combo would be marginally streetable mostly based on the 'intensity' of the camshaft. ie; if the idle vacuum is less than 9 inches this vehicle won't be a lot of fun to putt around in.
Don't see a problem with the 8.25" PROVIDING it has quality internals and the tolerances are perfect. The 'weakest links' would be the cap bolts and the (differential) spiders. I don't think you will be wanting a 'spool' so consider upgrading the sure-grip unit. Of course with slicks there may also be issues with the axles.
After-all, the first HP 360's had these rears from 1974 when they 'made some noise' (so to speak) in the NHRA stock and superstock classes and continue to do so.
Tough call but there are a LOT of (2 and 4-by) Daks with this type of rear and they seem to hold up. Again, tolerances AND lubricants can make or 'break' majority of rears.
How would you tell the difference?
I am guessing gears from either can go in between?
Sure grips interchange-able?
What do we want to avoid? I have some of the Data here..any experience?
Shims needed? <-Do they weaken the assembly?
Do you guys have a prefered brand of bearings or parts?
If I want to beat this car up on the back roads how long would a sure grip last??
I know that there are 27 & 29 spline axles-what exactly does that mean & in regards to interchange-ability?
69-96 are 27 spline
97-up are 29 spline <-from web
Back spacing ?
Are 8 1/4" limited slip units are ratio specific? ( 2.25/2/45 or 2.71 & up)
I have a volare road runner Awhatever package 360/727 car's axle, a 74 RR 8 1/4 axle, an 8 1/4 axle assembly from an a body 5 on 4.5 bolt pattern,
I have an F body i would like to run a more narrow axle with for wider tires. It has the 76 RR front suspension on it now and came with a floor shift manual. The car is getting a 360..
art # 542074 - Auburn High Performance Series - 8 1/4 & 8 3/8" Chrysler (2.71-up) -- 29 Spline <-worth it?http://www.moserengineering.com/dif...-series/8-1-4-chrysler-2-71-up-29-spline.html
Some data so far:
What is a good set of cruise gears?
http://www.forabodiesonly.com/mopar/showthread.php?t=243344
Rear Axles: Chrysler 8 1/4" Rear Axle
« on: January 01, 2008, 21:31:18 »
Chrysler Corporation's Spicer 8.25" rear was one of two differential types used in M-bodies, with the other being the weaker 7.25" unit. The 8.25" rear axle first appeared around 1969 in Plymouth Belvederes, Satellites and Dodge Coronets. The measurement refers to the size of the ring gear. This gear, which is turned by the pinion gear, changes the direction of the power being transmitted to it.
The pinion gear is turned by the driveshaft. From 1973 on, the 8.25" rear was used in virtually every rear wheel drive car model produced by Chrysler through 1989 and in trucks and Jeeps through the 1990s. Some truck versions were designated as 8 3/8" or 8.375", but many internal parts interchanged with the 8.25" unit. It should be noted that all 8.25" rear axle assemblies DO NOT necessarily interchange across all models due to different widths.
Built by the Dana Corporation, the housing is cast iron with tubular steel axle tubes pressed and welded in to form a complete carrier and tube assembly. The gear assembly is accessed by removing an inspection cover having 10 bolts. 8.25" axles use either the "7260" or "7290" style U-joints. All 8.25" rears had 3" axle tubes with large bolt pattern (5 X 4.5" bolt circle) axles. Units with a 2.45:1 gear ratio have a special case that will not accept any other gear ratio. The axles are retained by a c-clip on either side. All axles were 27 spline until 1997 when they were upgraded to 29 spline.
Although the consensus among many Mopar enthusiasts is that a Sure-Grip (limited slip) equiped 8.25" rear is good for up to 500 crank horsepower, it fares much better in street applications than the strip, and in lighter cars than heavy cars. Open 8.25" differentials are more prone to fail at higher horsepower levels than Sure-Grip units. The 8.25" axle has considerable aftermarket support since it was so widely used in the 1970s for performance use.
7.25" To 8.25" M-Body Swap (Originally posted by Malcolm)
If you currently have a 7.25" axle, the 8.25" axle will drop right onto the spring perch pad centers perfectly, requiring no modifications. On early M-body 8.25" rears, the measurement from the outside of the left drum to the outside of the right is one inch narrower than the later M-bodies, but there should be no tire clearance problems. As I mentioned in the old Forum, I run 7 inch rims and 225/70 15's without any problems and there is room for larger tires.
You will need:
- The donor 8.25" rear. The best bet for locating a sure-grip equipped unit at this point are any police, taxi or fleet cars (see Cop Car Information ). Good donors that will be more difficult to find are 1978 And 1979 LeBaron, Diplomat and Caravelle (Canada) Station Wagons. These cars were owned by families and are usually not punished as violently as former police or fleet cars. In most cases the axles are mint even if the bodies are rotted out (and the fake wood panelling is twisted by the sun). You can also hunt F-Bodies Aspen/Volare), older M-Bodies (Lebaron/Diplomat/Gran Fury) and J-Bodies (Cordoba/Imperial/Mirada) as they'll all drop right if you find the ratio you want.
- If available, get the driveshaft from a donor vehicle with a wheelbase and transmission similar to yours, i.e. 2-door, 4-door or wagon. If the driveshaft is not available, you will have to take your present driveshaft to a driveshaft shop, (along with the measurement from the transmission to the new rear end) and have it shortened or lengthened accordingly, and re-balanced.
It's also a lot safer to do a brake job on everything in the rear while you're at it. It would be smart to replace both the brake lines on the axle and the rear brake hose (from body to axle) while you're there. They're cheap and also easy to get at while the axle's out.
Great time to replace the rear shocks too if money permits. New axle U-bolts and a buddy to help you lift the axles out and in and you're all set.
If you find a 727 equipped 4 door M-body with the driveshaft in it, the front yoke will not fit your 904 transmissions spline. In addition the wagons will have longer drive shafts, which require shortening and re-balancing.
TRW makes a greasable heavy duty U-joint (part # 20124) that takes a beating and is well advised if you're going to spell your name on the highway in twin streaks of rubber (spelling "Malcolm" used to take a while until I installed the 360). Back to the U-joint. The nipple is on the end of one of the caps not in the valley of the inner cross where you can't get a grease gun on. Note: NEAPCO (New England Axle Product Company) also has one with the zerk in one of the caps.
Factory axle dimensions (7.25" and 8.25") for all F/J/M cars:
- Axle flange to flange: 54.34"
- Perch center to perch center: 44.46"
- 2.26:1 - This ridiculously high ratio was found in later M-bodies.
- 2.45:1 - This was the most common ratio for 1978-1979 M-bodies. It also appeared in many fleet cop cars through 1989.
- 2.76:1
- 2.94:1 - This was also common. Usually found in M-body police/taxi/fleet cars.
- 3.23:1 - This highly desirable ratio was not so common in M-bodies.
- 3.55:1
- 3.91:1
- 2.25:1
- 2.45:1
- 2.76:1
- 2.94:1
- 3.07:1
- 3.08:1
- 3.21:1
- 3.55:1
- 3.73:1
- 3.90:1
- 3.91:1
- 4.10:1
- 4.11:1
- 4.56:1
http://www.hemmings.com/mus/stories/2007/01/01/hmn_feature21.html
Feature Article from Hemmings Muscle Machines
January, 2007 - Jim O'Clair
We have written about plenty of rear-axle conversions for your consideration over the past few years. Earlier articles on Mopar differentials featured the 8 3/4-inch and 9 1/4-inch Chrysler units as well as the Dana 60. Because these three axle possibilities are getting harder to find and cost more, we recommend a less expensive alternative for your Chrysler product--the Chrysler 8 1/4-inch axle. The unit is commonly referred to as the 8 1/4-inch corporate axle. This differential is a Salisbury-type axle, meaning the ring and pinion can be accessed from the rear, as opposed to the Ford 9-inch or Mopar 8 3/4-inch, which are accessed by removing the third member from the front of the differential. Although not as strong as these other two units, they are reasonably easy to locate because Chrysler used them in a wide range of original applications and, secondly, this rear is much lighter than the Mopar 8 3/4-inch, without sacrificing strength.
Used extensively in passenger cars beginning in 1972, the 8 1/4-inch housing also was used in 1971 and newer Dodge B-vans and pickups. This differential is a great candidate for upgrading many Mopar 7 1/4-inch rear ends by adding strength without spending a lot of money. Original passenger car ratios ranged from 2.45:1 to 3.21:1. The truck 8 1/4-inch differentials had additional ratios of 3.55:1 and 3.90:1. A fuel-sipping 2.24:1 ratio was offered in some 1980-'81 passenger car applications, too. Aftermarket suppliers even offer 4.10:1 and 4.56:1 ratios, bigger than original equipment.
Two differential carriers were used in most of these axles. With the exception of the fuel-miser 2.24:1 ratio that we mentioned was used in 1980-'81, any other ratios smaller than 2.71:1 used one carrier and anything above 2.71:1 used a larger carrier. The housing is accessed from a rear cover that is about 11 1/4 inches across by 10 1/4 inches high and has an oval 10-bolt pattern. The pinion on the 8 1/4-inch axle is beefy. It measures 1 5/8 inches in diameter and has 27 splines. The Mopar 8 1/4-inch rear came without a limited-slip differential when it was first offered, however, it was offered in the 8 1/4-inch after 1973. There are also numerous suppliers which offer aftermarket limited-slip units, if an original unit cannot be located.
To determine if a rear axle is equipped with a limited-slip differential while it is still on the vehicle, jack up the rear of the car and place it on jack stands. Put the vehicle in neutral and spin one rear wheel counterclockwise while observing the other wheel. If it spins in the same direction as the wheel you are turning, it is a limited-slip rear. If the other wheel does not spin, you have an open-gear differential. A more obvious clue would be that most Chrysler rears would also still have the Mopar additive tag located on or near the rear cover, specifying the use of part number 4318060 limited-slip additive.
Passenger car (and most truck) axles are 27-spline and have a flange retainer that holds them to the end of the housing. The axle bearings were installed into the axle tubes and C-clips were used to hold the spline of the axle into the differential. This is similar to the Chevrolet, Buick, Olds and Pontiac axles; in fact, the axle bearing for the Chrysler 8 1/4-inch rear is the same for applications with a 2 1/4-inch axle tube (a 2.535-inch was also available). As with Chevrolet rear ends, the axle bearing can be its weakest link. The axle actually acts as the inner race for the rollers in the axle bearing, which can lead to premature wear in the axles themselves. There are repair bearings available which change the contact point on these axles once the bearing contact area on the axle becomes scored, and these repair bearings use an integral oil seal. Replacing the original two-part bearing and seal with this repair bearing assembly alleviates concerns about the strength or reliability of the 8 1/4-inch axles. The CR or BCA part number for the repair bearing is RP-1563-TAV. Performance replacement retainers are available to eliminate the use of the axle c-clips. The pinion yoke accepts a Detroit 7260-style U-joint the Spicer part number is 5-1306X.
Replacement yokes are also available from Spicer; part number 2-4-5851X. Several adapter joints are available to allow you to use the Detroit-style pinion yoke from the donor vehicle and still be able to use your original driveline.
You will most likely find a Chrysler 8 1/4-inch rears under the following cars:
- 1983-'89 Fifth Avenue
- 1976-'80 Aspen and Volare
- 1975-'83 Cordoba
- 1972-'76 Coronet
- 1973-'76 Dart, Duster, Scamp, Valiant
- 1977-'88 Diplomat
- 1983-'84 E-Class
- 1972-'78 Fury, Monaco
- 1973-'89 Grand Fury
- 1981-'83 Imperial
- 1977-'81 LeBaron
- 1980-'83 Mirada
- 1972-'82 New Yorker
- 1972-'81 Newport
- 1972-'73 Polara
- 1975 Road Runner
- 1979-'81 St. Regis
- 1975-'77 Royal Monaco
- 1974-'77 Ramcharger and Trailduster
- 1981-'90 B-200, 250 and 350
- 1971-'80 B-300
- 1969-'77 W-100, D-100, P-200, P-300
- 1971-'77 B-100
- 1983-'90 W-250 and W-350
- 1969-'78 W-300 and D-300
- 1974-'77 W-400
- 1981-'83 W-150
- 1978-'90 D-150, D-250
- 1972-'77 D-200
- 1981-'90 D-350
- 1987-'02 Dakota pickup
- 1997-'02 Durango
- 1902-'06 Jeep Liberty
We recommend you thoroughly inspect your donor differential before attempting an installation. Change the fluid and all seals and inspect gear teeth and bearings. If you have located a limited-slip differential, careful inspection of the positraction unit is also important. Should you need to replace any internal bearings, make a notation of the part numbers on them or find out the year the donor differential unit was produced. Bearing packages for the 8 1/4-inch rear are different, depending on if the axle was built before or after 1976. The 8 1/4-inch housing holds two quarts of 85W90 gear oil and, as with all Mopar locking rear ends, limited-slip units require 6 ounces of limited-slip additive.
Although lighter than the Chrysler 8 3/4-inch rear end, the 8 1/4-inch unit is heavier than some of the stock 7 1/4-inch Mopar 9-bolt assemblies it has been known to replace. You can transplant the 8 1/4-inch rear end in many non-Chrysler vehicles, too. Two- and four-wheel-drive pickup differentials will be 65 inches wide, making them compatible with earlier Mopar B-, C- and D-body cars, as well as full-size Chevrolet Blazers. The B-series van rear ends measure about 67 inches, which makes them a prime candidate for swapping into 1970s Ford vans. The 8 1/4-inch rear can be used in many street rod projects as well. C-body passenger car differentials are good candidates for 1935-'41 Ford pickups and 1940-'54 Chevrolet passenger cars. The Durango/Dakota 8 1/4-inch differentials measure 63 inches wide; however, the left axle is longer than the right axle and, as we have already mentioned, the axles are 6-lug. For ease of installation, we would not suggest using the offset Dakota/Durango rear end in earlier cars. But, the 8.25-inch Dakota differentials can be swapped between these two models. Original axle width and spring perch dimensions for most American cars and trucks are available in the parts locator section of our Web site; www.hemmings.com. This list continues to be updated as new information is received from our readers.
We checked with several used parts yards and found open differentials for mid-1970s A-bodies readily available for between $75 and $350. A rear end from a 1981 Diplomat cost between $125 for an open unit and $350 for a 2.94:1 with a limited-slip differential. Be aware that some used limited-slip differential units can sell up to $750. We recommend you first determine how big of a gear you want to run before buying one. If fuel economy is key, you'll want to find one with a 2.71:1 ratio or less. Changing gears later will cost less than $300. If you need a larger ratio for a work truck or heavier vehicle application, you will want to find a unit that has an original ratio of at least 2.94:1, so the carrier will work for any ring and pinion ratio up to 4.56:1. If you need to add a limited-slip differential to an open rear, Trac-Lok carriers for both 27- and 29-spline differentials begin at $250. Replacement parts, such as bearings and seals, can be easily found at a local auto parts store. On many applications, spring perches may need to be moved; however, this can be done easily with a welder. You can move the perches that are on the axle or purchase of a set of replacement spring perches through aftermarket rear-suspension suppliers. You should be able to locate these for less than $40 per pair. But, even with the purchase of a few items to beef-up your 8 1/4-inch donor axle, you are still way ahead of the curve if you consider that aftermarket 8 3/4-inch or 9 1/4-inch differentials sell for $1,200 to $1,500.
This article originally appeared in the January, 2007 issue of Hemmings Muscle Machines.
webwisdom "Sure they built 8 1/4 Sure Grips..Would I advise running one? Nope, not when there's 8 3/4's out there. You WILL break the 8 1/4" rear with a healthy small block, a Big block with destroy one."
webwisdom "Be careful with using later-model axles, too. I once tried swapping in a rear from a Volare into a '63 Valiant. The width was close enough, but it wasn't a bolt-in because A-body leafs have a big pin that sticks up and goes into a hole in the spring perch that locates the axle and keeps it from squirming around on the spring. I don't remember the details, but the Volare rear had some other way of accomplishing the same thing. I was able to locate another rear from an A-body, so I never bothered to solve the problem."
Webwisdom from:
http://forums.moparmusclemagazine.c...rear-end-how-much-is-it-good-for-torque-hors/
drmopar :This is a surprising decent rearend that has been overlooked by most. Just beware when buying
the posi, there are two different units. One for 2.41 and higher gears and one for the others. My brother has a 8 1/4 in his 14 second Duster. No issues. I have also seen them in a 12 second Aspen. The guy ran it this way for yrs. without any issue. He has a 360 making 450 horse with slicks.
The C-clips on the mopar rear end cannot drop out like a chevy
unit, so no need to worry about spitting out an axle.Good Luck.
68440Barry:
I have an 8.25 posi in my 74 pickup with a 67 440 and about 400 h.p. So far so good.
RBolig
I have a 4.10 geared 8-1/4 in the Dart Sport with a 400 hp small block and a four speed, and it's having no problems.
http://www.dodgecharger.com/forum/index.php?topic=84378.0
http://board.moparts.org/ubbthreads/showflat.php?Number=5610902
http://www.moparmusclemagazine.com/techarticles/drivetrain/5148_custom_rear_end_install/
https://www.allpar.com/forums/topic/87858-8-14-rearend/
Do you think that an 8-1/4 rearend with 3.91 or 4.10 gears and a limited slip would stand up to approximatly 450hp and 400 pound feet of torque from a 360 in regular street use with street tires? or with street slicks?
I'm inclined to believe that such a combo would be marginally streetable mostly based on the 'intensity' of the camshaft. ie; if the idle vacuum is less than 9 inches this vehicle won't be a lot of fun to putt around in.
Don't see a problem with the 8.25" PROVIDING it has quality internals and the tolerances are perfect. The 'weakest links' would be the cap bolts and the (differential) spiders. I don't think you will be wanting a 'spool' so consider upgrading the sure-grip unit. Of course with slicks there may also be issues with the axles.
After-all, the first HP 360's had these rears from 1974 when they 'made some noise' (so to speak) in the NHRA stock and superstock classes and continue to do so.
Tough call but there are a LOT of (2 and 4-by) Daks with this type of rear and they seem to hold up. Again, tolerances AND lubricants can make or 'break' majority of rears.
