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Rear end swap list.....let's make one


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Think I found my donor truck....93 Jeep Cherokee 4x4 for $300, can pull the rear diff, master cyl and some other parts like wireing etc....will make the build a lot cheaper.

Anyone upgrade their master yet to 2 resv. style? I know it will mean altering the pushrood and stock holes, but well worth it. I may even look at replacing to newer shackles and spring for the back....get rid of my 1 ton 1000 leaf system now.

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In the early posts the comment was that a Chevy diff would be desirable since the front discs would be from Charlie's kit.

I installed Charlie's kit on my 55 C-3-B8 and it used Volare rotors with the 5 on 4.5 bolt pattern. His kit does use GM calipers, so maybe that's the confusion.

I'm also looking for a new diff and was told by Randy's Ring and Pinon that truck differentials prior to 1957 may look like an 8-3/4 but that they were different and that he could not supply any gear sets for mine. My only choice is the original 4.10 or the OEM optional 4.86. So be careful about buying an old diff with the intetion of changing ratios.

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In the early posts the comment was that a Chevy diff would be desirable since the front discs would be from Charlie's kit.

I installed Charlie's kit on my 55 C-3-B8 and it used Volare rotors with the 5 on 4.5 bolt pattern. His kit does use GM calipers, so maybe that's the confusion.

I'm also looking for a new diff and was told by Randy's Ring and Pinon that truck differentials prior to 1957 may look like an 8-3/4 but that they were different and that he could not supply any gear sets for mine. My only choice is the original 4.10 or the OEM optional 4.86. So be careful about buying an old diff with the intetion of changing ratios.

You mean installing newer gears into a stock carrier?(pumpkin) I can see that that might be more difficult, so I think most would opt to just go to a whole new diff completely...as I am. Anyone know if Charlie's kit will work with jeep rotors? Wanted to try and keep everything the same for ease of ordering parts.

Will be ordering the kit in a few days anyway...

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Well after reading all the info on this particular post it looks as though there are no direct late model rear ends that will work on our pilot houses as a bolt in. I have a 48 with a spitfire 251 in front of it and would like to have a highway gear of about 350+ or something if I can find one here in my area I can afford. Junk yards around here became scarce when the steel price was up a year or so ago. It is hard to even find good parts on what is left.

Biggest problem will be finding someone who will cut and reweld the perches as I don't own a torch or trust my welding on something this critical. I'll keep just diggin and see what I can find that will satisfy old bessy.

Edited by tinlizzy
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I've heard Ebody mopars and early dakotas are a bolt in to 39-47 trucks. But I don't know how much the trucks changed with the restyle for 48.

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Well after reading all the info on this particular post it looks as though there are no direct late model rear ends that will work on our pilot houses as a bolt in. I have a 48 with a spitfire 251 in front of it and would like to have a highway gear of about 350+ or something if I can find one here in my area I can afford. Junk yards around here became scarce when the steel price was up a year or so ago. It is hard to even find good parts on what is left.

Biggest problem will be finding someone who will cut and reweld the perches as I don't own a torch or trust my welding on something this critical. I'll keep just diggin and see what I can find that will satisfy old bessy.

I wouldnt worry too much about the torching and welding...there is very little to be done, you can cut the old stuff off with a grinder and if you have a sketch of what you want any small welding shop should be able to do it very reasonably., literally 15 minutes of welding..It makes a HUGE difference in the drivability of the truck, ...the thing it appears I did wrong from someones previous response to my post was use the wheel cyl to set the pinion angle...(see earlier posts)...but it seems to work very well so I dont know...dont forget these are american pickups ..Not swiss watches we are working on...just give it a try...if it doesnt work..try something else, if you send me a PM I can email you a sketch of the perch layout for the cherokee axle...minus the pinion angle :)....good luck

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Although the pinion angle issue has been mentioned, it has not been given enough attention. The pinion angle must be kept very close to that of the engine/transmission (imagine a line straight through the crankshaft and trans tailshaft) so that the u-joints maintain similar velocities. This does not mean that you want a straight line completely through the engine-trans and rear axle. There needs to be an offset between trans and axle. The offset can be vertical, horizontal or at virtually any compass point, but it must be there.

Here is where a digital level becomes a valuable tool. The centre line angle of the engine and trans can be checked and then compared to the pinion of the stock axle. If these are the same, or very close, then check the angle of the spring perch. You now can compute the difference between the pinion and perch so that when you reweld the perch, the axle can be mounted anywhere, in the truck or on a bench, in virtually any position, and with your level you can establish the correct perch angle. No guessing.

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I know this sounds too simple, but I remember reading on the forum that someone stacked up 4 cinder blocks on a level surface, 2 on each side to support the axle.

Put the old axle on the blocks and let the pinion droop/hang down.

Then he did the same setup with the new axle, and using the old axle as a reference he placed the new perches at the same spot on the new axle as the old and bingo!

All lined up and ready to go in.

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  • 2 months later...

Today I just finished installing the center section from a '48 Windsor - 3:73 ratio - in my Pilothouse. I have 30-inch tall radials, and this comination lets me run just as fast as I like to keep up with freeway traffic. Wouldn't want the ratio any taller.

If you contemplate tis swap, it's a direct bolt-in, BUT you must use the Pilothouse axle housing. You the axle shafts along with the center section from the donor vehicle, and the pinion yoke from your original truck dfiveshaft. Took me several hours of fumbling to learn this lesson.

Also, the shop manual tells you how to adjust axle shaft end play with the shims behind the backing plates. What it does not tell you is that the two axle shafts butt ends inside the differential. You must adjust each axle separately, but with both axles installed. It is impossible to do just one axle. Ask me how I konw . . . .

Also, I have my old 4:57 rear complete with Windsof housing and brakes/drums that is free to anyone who can use it. Just call me if you're interested, and come pick it up - I won't try to ship it - it's heavy.

717-354-0276

Good Luick

Edited by grey beard
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I finished up my diff swap long ago...but only last week did I try to put the drive shaft on.....no idea what I was thinking there when I installed and didn't measure, but I think I was expecting the slide out portion to go out the extra couple inches I needed.

SO...anyone who converts a 1ton to a cherokee or jeep wrangler axle, be prepared to have a new shaft made up, or your old one extended...either way about $200-$500 depending on if you add or go new. You also have to get a conversion u-joint but that was easy, just took both to Napa and they came up with the right one.

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Like many, I have searched for a suitable replacement differential for my 55 C-3-B8. Yesterday's junk yard search revealed that for my truck the Jeep and Explorer diffs are too narrow. I don't know my original dimensions, but after converting the front brakes to discs with the kit from Oldaddy, my truck measures 62.5" between wheel mounting surfaces.

1987-90 Dakota pickups measure 63" between wheel mounting surfaces and are available in 3.21, 3.55, and 3.90 ratios. Units from 4X4 have the 8.25" Chrysler ring & pinion. Units from a V-8 powered Dak will be the 8.25HD. Now that I know what I need, the search is on to find one! The brake drums are small diameter, but are nearly 3" wide and have the 5 on 4.5" wheel stud pattern most of us need.

P.S. The Pick-N-Pull where I found the Dakota would NOT remove the diff for me at any price! I didn't have the tools or the inclination to climb under a wreck sitting on cement blocks to remove it myself. I don't know if others have similar experience with these types of yards.

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The 8.25 rear end of the Dakota can be easily brought up to a larger rear brakes by tranferring the backing plates and all associated brake components from the 7.25 rear gear as found on Diplomats and Chrysler 5th Aves..etc...I have the Dakota rear gear and upgraded brakes on my 51 Plymouth Suburban..

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if i remember properly, jeep cherokee rear ends are sometimes disk brakes, as it was an option, as was POSI-TRACTION, which i learned about after the fact. the jeeps are about 1.5" narrower, but nobody knows the difference.

The one I got from a 93 Wrangler was only about 3/4" narrower drum to drum...so nobody would ever know the difference...other then my 1 ton is way lower now...but also removed 4 leaves from the springs.

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I know this sounds too simple, but I remember reading on the forum that someone stacked up 4 cinder blocks on a level surface, 2 on each side to support the axle.

Put the old axle on the blocks and let the pinion droop/hang down.

Then he did the same setup with the new axle, and using the old axle as a reference he placed the new perches at the same spot on the new axle as the old and bingo!

All lined up and ready to go in.

The way I did that way back when was to put the old rear on the cinder blocks and measure from the center of the U joint on the old axle to the floor, write that measurement down, then put the new axle on the same cinder blocks on the loose perches and rotate until you get the same measurement and tack the perches in place.

That will give you the same pinion angle as the old rear end.

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Using two levels and a speed square to ascertain what angle the pinion in my 36 Plymouth rear end sets in relation to the spring perchs. A small level on the perch, a level set across from the top of the pinion, and a line up straight with the face of the pinion with the speedy, and a mark on the level, which shows 5 degrees angle. Joel

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I just bought a cheap angle gauge...lol...can't remb the proper name this moment, but I just set the truck in it's typical position then measured it...found only about 1-2 deg on my 1 ton and perfect flat in other spots...so I just set my pinion level and the adjusted the perches to match...HOWEVER...remember that when the vehicle is under power the rear diff tips up so you will want to somewaht compensate for that or you can get some vibration....but 1-3 deg. is about all you need to figure out......so what I'm saying is don't weld them with the pinion in an up spot...make sure it's down so when the power sets in it's riding close to where the old stock one was at stop.......confused yet?

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the angle of the pinion is not relevant to the car, it is relevant to the angle of the transmission output shaft..the phasing of these two components is the prime consideration of the these angles and is determined by imaginary lines through the pinion shaft and the transmission, these need to be parallel (not a direct line) to each each other..same consideration is taken even if components are offset of each other..

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I don't understand the vehicle, it being level, or measurements relating to how far the pin sets off the floor, ect., having anything to do with it either. If the goal is to re-set the new rear end in the same location as the old (which is assumed to have been working) then, all of the consideration is simply where the perches are in relation to the angle of the pinion on the rear end, and getting the new setup as close to the old as possible, right? If that is accomplished, than all the other variables such as load movement, ect should also be the same as they were originally, shouldn't they. It is actually not even neccasary to KNOW what degree the angle is, just to replicate it, so all it takes is a tape and two levels, and no other special tools, or measurement devises. A sliding T-bevel would work just fine, or just getting a good mark on a board, ect.

Installing a rear end is about as simple as it gets working on anything, to me. I don't measure anything until I have it out and on the ground, and then it's just the distance out to the center of the perches from the center of the diff, (checked as an over-all measurement, and also the same in from each hub, ect.) , then get the angle like in those pictures above, then reset them to the same setting on the new rear end, which I did by attaching an upright to the yoke of the "new" one, clamping that in a striaght line to the mark on the level I made with the old one, set it level, (thus establishing the angle on the yoke, then setting the perches in their designated places using the small level.

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Yes, yes , yes and yes. When you're replicating the original, that's all that's necessary. Some of us can't leave well enough alone (:D) and start changing things around from where they used to be and that's where the engineering and physics principles have to be paid attention to.

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Joelokie...what you are saying is basically true "if" the intent is to swap just a rear gear this is pretty much as you descibe..however I must point out the one varaible in your statement that could prove to be a bit of problem and granted may be but slight in most cases "assuming it worked (was correct phase) to begin with" to know a car was correct by its driving characteristic prior to the change is an excellent starting point..dropping the driveshaft and doing a static check of the phasing prior to removal of the rear gear would be prudent..especially with the age of these cars and unknown practices of the PO and unknown or excessive wear/compression of the original rear mounts.

correct phasing of the drive shaft is the measured parallel lines of the components in relation to height and offset and if any drive shaft be cut and reconnected with new flanges..the u-joints must also be in alignment to take advantage of full deflection of the u-joint without bind and damage...technically at most driveshaft speeds seen by a street car vibrations is not a major factor at 2-3 degree error..however if you get weak chassis components and extended travel of suspension on acceleration the angel will flex and can cause problems..short life of u-joint, and bad vibes/tramping is some of these negatives..I have seen some pretty bad examples of out of phase drivelines and their resultant damage and bad ride qualities..

All in all you should be safe in your approach but nonetheless should be measured in realtion to the driving component just to be a bit leaning to the safe side you might say...and you would not believe the number of transplants I have seen that have not taken this phasing into account..close can get you a cigar but it may be difference in a fine Cuban compared to a hobo's used stogie..

Edited by Tim Adams
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