Rear end

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It's clearly an 8.25 which is plenty strong. If you're just itching to spend money, send me a grand and say you have an upgraded rear end.
 
RustyRatRod said:
It's clearly an 8.25 which is plenty strong. If you're just itching to spend money, send me a grand and say you have an upgraded rear end.
Click to expand...
What that was probably the most useless advice I've got so far..Good try tho
 
504DusterIR said:
What that was probably the most useless advice I've got so far..Good try tho
Click to expand...
Well, I did nail down that it IS an 8.25. All everybody else did was that "looks like" crap. Useless? Maybe I'll remember you said that next time you ask for advice.
 
You know, I see you just itching to spend money with no real idea why your combo is soft.
You need to figure a few things out first.

number one is to check out your engine;
do a compression test.
While the plugs are out, look at them!
then check the power-timing.
then make sure that when you floor the gas pedal, that the 4bbl actually opens all the way and that the choke is not stuck on, that your exhaust is open, and that your engine is coming up to a decent working temperature.
One dead cylinder is 12.5% soft.
All 8 cylinders at 10% leakdown is almost the same as one dead cylinder.
Maybe you have a burned valve, or a bad cam, or just crappy cam timing. or a plugged exhaust.
These are the basics
Number two is the trans
do a stall tested and an efficiency test.
Number three is the rear end;
figure out exactly what ratio is in there
Number four is the chassis.
Make sure the brakes are not dragging, that the U-joints are ok, empty your trunk, leave your porky friends at home, and air up the tires.
number five is inlet air
What elevation are you at?
What size is your Magnum, for sure?
How is she getting air?
and is she getting enough air?
The hardest part to making power is getting the air in.
And finally;
Who told you your combo was soft?
That's a trick question.
If you told yourself it was soft, then soft compared to what?
If somebody else told you it was soft, do you trust his judgement?
 
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Put the rear of the car on jack stands. Check the rear ends bolts for a metal tag that will state the ratio within. If it is not there, continue with the following.

Chock the front tires, then the trans in neutral. Rotate the rear tires and count the driveshafts revolutions. This will come up with the approximate gear ratio. A white out pen is good to mark the driveshaft.

Or, take the cover off and service change the rear end oil.

To swap gears and the differential, parts are available. Suregrip units are reasonably priced as well as the ring and pinion.

On we all know what the ring & pinion ratio is, true & better suggestions can follow. FWIW, I also will suggest a upgraded torque converter well after the gear swap, if the new ratio doesn’t do it for you.

Considering you said it is a daily driver, I wouldn’t use a ratio above 3.21/3.23. I’m also assuming you may see some interstate driving.

Where in Fl. are you?
 
what kind of driving do you like to do? run on the freeway and keep up with traffic? run hard from 0-60? get an idea of what you want your cruise speed RPM with a calculator like this: https://www.tremec.com/calculadora.php

keep in mind, this will estimate cruise RPM probably 100-150RPM low, because this calculator does not take converter slip into play. try figure out your current ratio as well, to determine what ratio you may want to go to.

IF you decide to replace the rear, you can probably sell your current one for a decent amount, I'd be interested if it was in indiana, michigan, or ohio....don't know what the A body parts situation is down there, but up here, you can't find much. your best bet for upgrading the rear is to look towards a ford 8.8 out of a ranger or explorer, especially if you want to move to a 3.55-3.73 ratio, disc brakes, etc....a lot of them are sitting in the junkyards with limited slips, too. an A body 8.25" is about 57" or so drum face to drum face. a ranger rear is 58.5" mount face to mount face, an explorer is 59.625". the ford axles have the pumpkin offset, if you shorten one side to center it and use the same side axle shaft on both sides, it ends up being 56.625".

XJ 8.25's are an option, too. autos are mainly 3.55's, manuals 3.07, might find a tow package with a 3.73, might find with a limited slip....only problem is they're 60"-60.5" drum face to drum face, which means you'll need to use high offset (like +30-45mm later model mustang) wheels to not have the wheels hang outboard of the fenders.
 
Is this a option?
Take the guys out of the Jeep rear and use it in the one you have?
 
RustyRatRod said:
AJ/FormS said:
You know, I see you just itching to spend money with no real idea why your combo is soft.
You need to figure a few things out first.

number one is to check out your engine;
do a compression test.
While the plugs are out, look at them!
then check the power-timing.
then make sure that when you floor the gas pedal, that the 4bbl actually opens all the way and that the choke is not stuck on, that your exhaust is open, and that your engine is coming up to a decent working temperature.
One dead cylinder is 12.5% soft.
All 8 cylinders at 10% leakdown is almost the same as one dead cylinder.
Maybe you have a burned valve, or a bad cam, or just crappy cam timing. or a plugged exhaust.
These are the basics
Number two is the trans
do a stall tested and an efficiency test.
Number three is the rear end;
figure out exactly what ratio is in there
Number four is the chassis.
Make sure the brakes are not dragging, that the U-joints are ok, empty your trunk, leave your porky friends at home, and air up the tires.
number five is inlet air
What elevation are you at?
What size is your Magnum, for sure?
How is she getting air?
and is she getting enough air?
The hardest part to making power is getting the air in.
And finally;
Who told you your combo was soft?
That's a trick question.
If you told yourself it was soft, then soft compared to what?
If somebody else told you it was soft, do you trust his judgement?
Click to expand...
I told myself it was soft ,before I build the duster I daily drove a 2008 Saturn 2.4 engine an it ms definitely more quicker
Click to expand...
michiganpat said:
what kind of driving do you like to do? run on the freeway and keep up with traffic? run hard from 0-60? get an idea of what you want your cruise speed RPM with a calculator like this: https://www.tremec.com/calculadora.php

keep in mind, this will estimate cruise RPM probably 100-150RPM low, because this calculator does not take converter slip into play. try figure out your current ratio as well, to determine what ratio you may want to go to.

IF you decide to replace the rear, you can probably sell your current one for a decent amount, I'd be interested if it was in indiana, michigan, or ohio....don't know what the A body parts situation is down there, but up here, you can't find much. your best bet for upgrading the rear is to look towards a ford 8.8 out of a ranger or explorer, especially if you want to move to a 3.55-3.73 ratio, disc brakes, etc....a lot of them are sitting in the junkyards with limited slips, too. an A body 8.25" is about 57" or so drum face to drum face. a ranger rear is 58.5" mount face to mount face, an explorer is 59.625". the ford axles have the pumpkin offset, if you shorten one side to center it and use the same side axle shaft on both sides, it ends up being 56.625".

XJ 8.25's are an option, too. autos are mainly 3.55's, manuals 3.07, might find a tow package with a 3.73, might find with a limited slip....only problem is they're 60"-60.5" drum face to drum face, which means you'll need to use high offset (like +30-45mm later model mustang) wheels to not have the wheels hang outboard of the fenders.
Click to expand...
All this is very good Information ,I'm at work an then I going to school right after so after I'll try to respond, I drive to work an school no highway driving done yet ..the fastest speed limit is 55 mph
 
Go to a self serve car wash with spray wands, and blast all that crud off the cover. Be prepared to get splattered with some of it....lol. If you get that junk off the cover and bolts, you will be able to see the gear ratio tag unless someone has removed it. I'll start the betting that it's 2.45 gears! :eek:
 
JDMopar said:
Go to a self serve car wash with spray wands, and blast all that crud off the cover. Be prepared to get splattered with some of it....lol. If you get that junk off the cover and bolts, you will be able to see the gear ratio tag unless someone has removed it. I'll start the betting that it's 2.45 gears! :eek:
Click to expand...
Yea I was thinking my gear ratio is of that, some charts that was sent to me say that small block V8 passenger car had gear ratio in the 2's
 
rumblefish360 said:
Is this a option?
Take the guys out of the Jeep rear and use it in the one you have?
Click to expand...
guessing you meant "take the gears"....

not sure if there were any differences/changes that happened between the early 70's and early 90's that might preclude that....IIRC there were some major changes to the 7.25" in the late 70's that made stuff like that not swappable.
 
What I would do first (after the GREAT advice to clean it first!) is pull the cover off, and actually see if it has a suregrip, and what ratio it is. Then put some appropriate fresh fluid in it, and decide what you wanna do.
I agree, the 8 1/4 should be fine, with a sure grip added, and a reasonable gear.(3.23/3.55)
For a stronger rearend? HERESY!, but I would suggest a mustang 8.8. As strong as a 8 3/4, much more available, and MUCH cheaper. You can find them with disc's, "posi's" and good gears. An explorer rear works too, if you narrow one side and use two short axles.
 
JDMopar said:
Go to a self serve car wash with spray wands, and blast all that crud off the cover. Be prepared to get splattered with some of it....lol. If you get that junk off the cover and bolts, you will be able to see the gear ratio tag unless someone has removed it. I'll start the betting that it's 2.45 gears! :eek:
Click to expand...
mark me down for 2.76.
 
33IMP said:
What I would do first (after the GREAT advice to clean it first!) is pull the cover off, and actually see if it has a suregrip, and what ratio it is. Then put some appropriate fresh fluid in it, and decide what you wanna do.
I agree, the 8 1/4 should be fine, with a sure grip added, and a reasonable gear.(3.23/3.55)
For a stronger rearend? HERESY!, but I would suggest a mustang 8.8. As strong as a 8 3/4, much more available, and MUCH cheaper. You can find them with disc's, "posi's" and good gears. An explorer rear works too, if you narrow one side and use two short axles.
Click to expand...
33IMP said:
What I would do first (after the GREAT advice to clean it first!) is pull the cover off, and actually see if it has a suregrip, and what ratio it is. Then put some appropriate fresh fluid in it, and decide what you wanna do.
I agree, the 8 1/4 should be fine, with a sure grip added, and a reasonable gear.(3.23/3.55)
For a stronger rearend? HERESY!, but I would suggest a mustang 8.8. As strong as a 8 3/4, much more available, and MUCH cheaper. You can find them with disc's, "posi's" and good gears. An explorer rear works too, if you narrow one side and use two short axles.
Click to expand...
I came across articles talking about using mustang 8.8 an I also saw a video on youtube where they used a Ford rear end but had to shorten some parts an an short axles an they ended up cutting the flange an moved them not sure inward or outwards to fit, Now with the mustang 8.8 what modifications would need to be made ?
 
504DusterIR said:
I came across articles talking about using mustang 8.8 an I also saw a video on youtube where they used a Ford rear end but had to shorten some parts an an short axles an they ended up cutting the flange an moved them not sure inward or outwards to fit, Now with the mustang 8.8 what modifications would need to be made ?
Click to expand...
How would I tell if it a suregrip ? An I'll watch some videos on how to take cover off ( is it as simple as removing the ten bolts) an how to change fluid, most likely would benefit from a fluid change ( not sure when or if it has ever been changed, Im off from school tomorrow so if I get time I will wash it an possibly take it apart an send more photos
 
I know someone was asking above where I'm at and the sea level? Im Okaloosa County FL
 
The mustang rear could probably be used, as is. The explorer rear uses a long axle and a short one, and needs to be narrowed (probably cheaper than a mustang). You don't mess with flanges, you take a section out of thelong axle side, and use another short axle.
You would probably have to shorten your driveshaft and adapt for a ford size u-joint. Also, of course, remove the four link stuff off the mustang, and add new leaf spring pads. Explorer still uses leafs, but the pads will still have to be moved.
Unless you feel you NEED more beef, getting your 8 1/4 squared away is a better idea. Im gonna use an 8.8 explorer under my 57 chevy sedan delivery with a 454, in place of the plastic stocker. (NOT really plastic, but you get my meaning).
 
michiganpat said:
guessing you meant "take the gears"....

not sure if there were any differences/changes that happened between the early 70's and early 90's that might preclude that....IIRC there were some major changes to the 7.25" in the late 70's that made stuff like that not swappable.
Click to expand...

The spine count change on the axles.
There is a slight difference in the ring gear to allow anti spin/anti lock.
They are swapable from what I understand.
This is worth checking into.

504DusterIR said:
How would I tell if it a suregrip ? An I'll watch some videos on how to take cover off ( is it as simple as removing the ten bolts) an how to change fluid, most likely would benefit from a fluid change ( not sure when or if it has ever been changed, Im off from school tomorrow so if I get time I will wash it an possibly take it apart an send more photos
Click to expand...

Raise the rear end of the car with jack stand under each side suspending both wheels like I said early and spin a tire. If the other tire spins with it, it’s a suregrip (posi) if the other tire spins against the tire your spinning. It’s a peg leg.
 
'96 and later Chrysler Corporate rear 8.25 10 bolt changed from 27 spline to 29 spline. The Ring and pinion stayed the same throughout the years into the 2000s... There is a carrier break though.. if you have 2.45s the higher ratio gears will not bolt up to that carrier. look for 96 and older for guts. 3.21 or 3.55s should serve nicely.
 
Ok so much good info so much research to do an process, So with all the info so far would it be cheaper an easier to change out the gears in the 8.25 I have ,I have yet to clean it an open it but I also have my bets on it being 2.76 and if not sure grip I install it an change the gears ? I hope y'all understand what I'm trying to say lol
 
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