Building my first 8.25 rear..

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DusterKrazy

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I am fixing up an 8.25 rear for a mild 318 car. I have the correct SureGrip for the factory 2.45 gears and will of course use the original ring and pinion which is in excellent condition. Is there anything I need to know when tackling this project??
 
2.45 gears? You sure U really want those--that car is going to feel like 6,000 lbs taking off from the light. Oh sure, @ 75 mph it be OK, in fact really nice--problem is getting up to speed. It would be OK in 75 mph zones were you can go 85--90 and 2nd gear would be 3.55 so it pull to 125--130 nicely--once its at 90...

traffic sadly doesn't move that quick up here
 
you need a sure grip with that ratio?
OK..make sure you take a backlash measurement BEFORE you take it apart...and use some gear marking compound to put it back exactly where it was..or you will have noisy gears! Very important with used ones...
Get a service manual if you dont already have one...
 
You need a different carrier also to run 2.73's and up.

If you going to set the gears up you should try to find a 2.73 gear and carrier Junkyards, should be cheap, $50--$75 if the place is fair. If they have any mopars out there, lots of 4 door cars had 8 1/4 rears.

With 2.45 the engine is going to lug most of the time. If you hardly ever floor it work ok, you might get 20 mpg on the freeways but 2.73's will be close and feel a little better. Won't hurt to look around, ebay also but then there is shipping costs, too much.
 
FYI - You can build the axle adjusting tool for cheap from your local hardware store.

I bought a 36" length of steel plumbing pipe, ground the threads off it, and hammered a proper size nut on each end. Then I welded it just for GP, but considering it needed a hand sledge to get them on, they weren't going anywhere. Total cost: $18...and it works on 9.25s also, for us truck people.

AxleTool.jpg
 
DusterKrazy said:
Nope..I don't have that. Thanks for mentioning...

As far as the gear goes, It is all I have and it's all I can afford. I have no desire to leave the 7.25 in there.
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Got a 2.71 ring and pinion and open carrier you can have for the cost of shipping. I'm upgrading an A Body 8.25 to a 3.21 with a Sure Grip and Grand Cherokee rear disc brakes.
 
65 Dartman said:
Got a 2.71 ring and pinion and open carrier you can have for the cost of shipping. I'm upgrading an A Body 8.25 to a 3.21 with a Sure Grip and Grand Cherokee rear disc brakes.
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Would the 2.71 case fit into my 8.25 housing? I heard the case maybe different?? or is it the carrier only??
 
What I have is the ring and pinion gears and the open carrier that the ring bolts to. I "think" the gears I have will bolt to your sure grip but don't know for sure. Someone more knowledgeable than I on the 8.25 will surely chime in.
 
If its a real mild car, you can get away with an early jeep cherokee 8.25 trac lok LSD. That's what i have in my car. So far its working pretty good.
 
dodge freak said:
2.45 gears? You sure U really want those--that car is going to feel like 6,000 lbs taking off from the light. Oh sure, @ 75 mph it be OK, in fact really nice--problem is getting up to speed. It would be OK in 75 mph zones were you can go 85--90 and 2nd gear would be 3.55 so it pull to 125--130 nicely--once its at 90...

traffic sadly doesn't move that quick up here
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Really? it'd be that awful? even with the 2.94 low gear in the 904?

My buddies Diplomat with 2.24 gears and some mods isn't that terrible IMO. Yes, it will flat out haul on the top end!!:prayer:
 
chances are his trans doesn't have a 2.94 first gear. Those were used in the 80's when 2.45 gears were common. Not all 904 trans have 294's many were the 2.45..which I like better cause 2nd is 1.45...with the 2.94, 2nd is 1.54, the engine bogs down on the 1--2 shift, not squeal the tires like the 2.45 to 1.45 shift.

Carriers all fit but from 97 on up the axles are 29 splines, the older axles are all 27 splines, so you need a 96 or older carrier.
 
dodge freak said:
chances are his trans doesn't have a 2.94 first gear. Those were used in the 80's when 2.45 gears were common. Not all 904 trans have 294's many were the 2.45..which I like better cause 2nd is 1.45...with the 2.94, 2nd is 1.54, the engine bogs down on the 1--2 shift, not squeal the tires like the 2.45 to 1.45 shift.

Carriers all fit but from 97 on up the axles are 29 splines, the older axles are all 27 splines, so you need a 96 or older carrier.
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The car I am putting the rear into has a rebuilt 904 with the low 1st gear. I have a truck rear with 3.55's laying around. I heard that another carrier will not fit into my housing because a 2.45 has a specific housing????
 
Carriers all fit.

Certain carriers are used with 2.45 gears, for 3.55 you need the 2.73 and up carrier.

the 3.55 will slip right in but if its from these newer suvs--1997 and newer, the carrier fit and all but the axles will not go back in. You need an older pre-1997 27 spline carrier. if its got abs ring the axles will NOT fit

But all carriers fit all housings, its gears and axles that may not.

3.55 would be prefect expect for long highway drives @75 mph plus. It feel like a different car compare to the 2.45's.

Oh by the way, 80% of these newer cars have such poor acceleration after 80 mph its hard to judge how quick your car is. I'm sure that Dip with 2.24 does seem good at high speeds but a 2.94 gear would pull even better and still be good for 140--if the engine has that much power.

with your 2.94 1st gear, 3.55 would be it, 3.91 would be too much but I done it, had a "dead spot" after the 1--2 shift... 2.45 would be livable with the 2.94 1st
 
dodge freak said:
Carriers all fit.

Certain carriers are used with 2.45 gears, for 3.55 you need the 2.73 and up carrier.

the 3.55 will slip right in but if its from these newer suvs--1997 and newer, the carrier fit and all but the axles will not go back in. You need an older pre-1997 27 spline carrier. if its got abs ring the axles will NOT fit

But all carriers fit all housings, its gears and axles that may not.

3.55 would be prefect expect for long highway drives @75 mph plus. It feel like a different car compare to the 2.45's.

Oh by the way, 80% of these newer cars have such poor acceleration after 80 mph its hard to judge how quick your car is. I'm sure that Dip with 2.24 does seem good at high speeds but a 2.94 gear would pull even better and still be good for 140--if the engine has that much power.

with your 2.94 1st gear, 3.55 would be it, 3.91 would be too much but I done it, had a "dead spot" after the 1--2 shift... 2.45 would be livable with the 2.94 1st
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The extra axle is from a '78 Dodge truck. I think it might work??
I have heard the carriers won't fit into the 2.45 housing..I just don't know...
 
The carrier bearings changed in 76, the OD got bigger but the ID stayed the same. If your trying to put a newer carrier into an pre-76 rear or vice-versa you will have to use the right bearings for the rear that you are working on. I dont see why a 2.76 and up carrier wouldn't fit in a 2.45 housing, I always thought the 2.45 gears wouldn't fit into the 2.76 housing because of the massive pinion gear.
 
Hoping to re-open this discussion for still more advice. I too have similar issues: scored a '73 complete suspension from a Dodge Dart for Big Red, 8.25 rear with 5 leaf springs, 2:71 open rear (size confirmed), BBP, big discs up front, big drums in the rear, correct A-arm, yadda yadda.

Happy with it and the price. All stuff in excellent shape. Sent the rear out to a local reputable shop to rebuild and set up with the off-a-shelf, NOS 8.25 Sure Grip that came with all the other goodies. . .comes the sad report in today: the carrier is .25" shorter than the open carrier at the ring gear mount when they are set side by side; the carrier adjuster ran out of adjustment trying to set the pinion gear tooth depth of engagement. There does not commercially exist a spacer, and longer gear retaining bolts would be needed as well- not that that is advisable anyway.

Apparently, I came away with a "jackpot" of sorts: the NOS Sure Grip I scored is for '70-'74 8.25 rear with 2.52 or 2.45 ring and pinion! In other words, it is a paper weight or boat anchor; who would want Sure Grip in those gears? I can return it for the $100 I got it for, but that's all he has available (closing parts warehouse deal).

Actually, I want the 2.71 for fuel economy and low RPM on Texas Highways at 80 mph (Besides, I already own the gearset!) ;-) Car is set up with poly bushings, frame ties, Formula S springs and torsion bars, performance shocks and front and rear sway bars to cut nice corners at speed in the Hill Country around Austin. Maybe do some light parking lot cone rallys some day. The 2.76 gearset (original was a 7.25 rear with a Sure Grip! Go figure. . .) formerly under it did well enough for acceleration in first in the 904 for over 300,000 miles of my abuse. . .and it worked okay with the mildly worked 318 I have in it now. . .but it was tired and needed a change to something heavier.

Now my choice to finish this part of the build seems to be Eaton Truetrac or open rear. Seems Mopar Performance does not offer a Sure Grip for anything taller (numerically lower) than 2.76. . . So says their website. . .

So, who likes Eaton Truetrac, is it worth $400 more on this money hemorrhage I'm into, will it make any real difference in how the car drives and corners enough to notice? I know a number of us here do auto cross and road rallies- what do you do for your rear end with regards to driving those corners? Probably very seldom see snow or ice, seldom rain slick streets- but it will be driven.

Thanks as always guys and gals. I haven't been on here for far too long due to various personal hills to climb this year. . .but still plugging along on her here and there. Just passed 2 years in a 1 year personal finishing goal. . .you know the drill.

I know, I know- Pictures!

:-D

Mike
 
The Eaton Truetrac is the best LSD for cars used on the street, road course or auto-cross bar none. It's strong, doesn't wear out and it's operation is seamless. Not the cheapest, but the best.
BTW, it doesn't need whale snot gear oil additive either.
 
lrazor said:
The Eaton Truetrac is the best LSD for cars used on the street, road course or auto-cross bar none. It's strong, doesn't wear out and it's operation is seamless. Not the cheapest, but the best.
BTW, it doesn't need whale snot gear oil additive either.
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Happens Mr. Ehrenberg replied about the same way:

"I'd go with the TorSen diff (TrueTrack) in a nanosecond. And that 2.76;1
gearset will be sweet, don't be talked out of it! ( I mis-typed the gear ratio to him).


Look back at the ScatDak series for diff setup hints...that axle is SUPER
easy to work on!

But....the rear sway bar might be overkill, inducing oversteer. Won't really
know until you try it though.

Hopefully you scored the Dart's spool-motor-mount, double-shear idler arm
K-member, too."

Thanks Irazor. Just got to find something to sell to make it happen- my rear builder is waiting.

Mike
 
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