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Unread 09-18-2013, 07:45 PM   #1
ZJLimited318
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1994 ZJ 
 
Join Date: Dec 2010
Location: Racine, Wisconsin
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1997 Laredo, bad rear diff

Well, I've got a ZJ again.

This one has a bad rear diff, binds up and u have to back up and can only go about 4 feet at a time or it'll lock up.

Don't want to mess with it, just want to swap the whole thing out.

Only problem is the dang thing is the dana 35, with 3.55 gears. Great! Closest diff I can find is 60 miles away and its $400. Thats seems crazy money for a rear diff with 150k.


So what I'm wondering is if I picked up another jeep (junker) and it turned out to have a dana44 3.55 or d35/d44 with 3.73.

Could I just swap both axles to make it work? But then would the driveshafts still have the correct hookup to the transfercase?

I looked on car-part.com and it shows 8 different front diffs and multiple different types of driveshafts. Really don't want to bite the bullet for a $400 rear end when I can get a whole dang jeep for that.

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Unread 09-18-2013, 08:17 PM   #2
jabba974
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Make sure that both front and rear have the same gear ratios...Check out cars-parts.com It is a salvage yard parts locator, I have used it alot to find parts near me...

Edit: didn't read the part where you looked there..lol There should be a tag on the axle that would identify your axl...either that or pull off the diff cover and count the teeth on the ring gear and divide it by the number of teeth on the pinion... You might be able to find out whats bad..if its just the spider gears, then that might be an easy fix...ring gear, not so much...
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Unread 09-18-2013, 08:26 PM   #3
ZJLimited318
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It feels pretty bad. You can only move a couple feet forward and the rear end completely locks, back up a foot and it unlocks, to let you go only a couple feet forward.
Fun! haha But its a real nice truck otherwise.

I already know I have a dana 35 with 3.55 gears, as mentioned in the first post. Was hoping to get another ZJ for parts and was wondering how much problems I'd run into just swapping most axles say if I got a set of 3.73's. And then not sure if I would have right driveshafts to bolt to 242 t-case?
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Unread 09-18-2013, 11:03 PM   #4
stovie
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I'm not to sure about how to do the swap but my sister has had bad experience with the back rubber seal getting hard, start leaking oil and end up killing the diff. It was making a whining sound so she took it to a mechanic to check it out and he said it was fine, two weeks later it died and had to be rebuilt that happened three times so she sold it to me for $450
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Unread 10-01-2013, 12:12 PM   #5
ZJLimited318
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So does anyone know what would be involved with trying to swap both axles?

Seems most parts trucks I find are V8 3.73 truck and I've got 4.0 3.55.
Or would it be better to find a replacement like I already have?
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Unread 10-07-2013, 03:26 PM   #6
stovie
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Have you drained the diff and checked the teeth?? I was just thinking you could see about draining the diff(getting the chunks out if it's not a problem with the teeth themselves) and then see about driving it after if possible?? I mean what more could happen after that?? Break it more then it is already?
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Unread 10-07-2013, 04:13 PM   #7
MyZJ98
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Sounds pretty bad locking up so hard like that. If its staying parked with plans to swap, pull the cover and see what you find. Maybe you will be surprised and its something much less than you'd expect.

Regardless, just swapped my d35 with 3.73s last week. To avoid modifications including welding, your only swap options for the rear end would be a d35 or d44a from another ZJ. The only thing that will matter is the gear ratios, all the rear ends are the same size, no matter what motor, trans or t case you have, so don't sweat that so much. Just search Craigslist and car-part.com for similar year d35's or d44a's with the same gear ratio as your front. As mentioned, if you don't already know it, the gear ratio should be stamped onto a metal tag on the axle itself, typically found on the diff cover. Once you source a new rear end with matching gears, you just gotta swap it out.

The swap is pretty straight forward, just take your time on everything. Here's s simple break down:
Before lifting, loosen all control arm bolts ahead of time.
Lift it as high as possible by the body and support with jack stands, so the axle can droop.
Remove wheels and driveshaft from rear end, and let the axle droop.
Disconnect shocks, sway bar links, track bar at the axle, and upper control arms.
Remove brake calipers and zip tie to body, remove rotors.
I had to swap brakes on mine, but that's a whole other thing.
Disconnect the misc stuff from axle like diff breather, abs lines and brake lines & brackets. Carefully lift an zip tie outta the way.
Disconnect lower control arms and pull old axle old.
Slide new axle under, and replace in reverse order.

Really not bad, just a matter of taking things off and putting them back. Replace what you break along the way. Make sure you cover everything in PB blaster or oil a week in advance, every day until you do the swap, you will see why...

Right now, just focus on finding yourself a new rear end with correct gears, and maybe lower mileage (although mileage doesn't necessarily matter on a well cared for rear end, might even find one with newer bearings...). Expect to pay between $150-$250 for a used rear. I wouldn't pay much more than that honestly.

Hope that helps a little, I'm no pro, but was forced to do this swap myself last week with little time to prepare and perform. Not a bad job overall.

Good luck
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'98 ZJ Laredo, 4.0L, 140K, NP242, stock. (Sold @205k)
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'97 ZJ Limited, 4.0L, 109K, NP249, stock.(Current)
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Unread 10-07-2013, 05:08 PM   #8
lionshooter
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Same problem with my 93. Pinion bearing disintegrated and it locked up. I found one today at U Pull it for $70. Same axle, also on a 93. Same 3.55 ratio. Clean and tight, so I am going to go for it.
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Unread 10-17-2013, 10:35 AM   #9
ZJLimited318
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Here's my problem though. This jeep has 3.55 gears which seems to be "very rare" around my area at least. Found a couple but they want $350-$400. No way I will pay that when I can get a whole other jeep for $500 or so.

Thats why I was asking, if I just got a whole different jeep that had 3.73 gears, could I just swap both axles. My only issue is I'm worried I wont have correct driveshaft or something. As I was reading there were many different types of driveshafts used.

Car-part.com shows:
1997 front DS options
6 cyl, NP249 transfer case (CV type Fr joint, u-joint type Rr joint)
8 cyl
6 cyl, NP242 transfer case (U-joint type joints)

1996 Front DS options
4.0L, CV joint style Fr yoke, from 11-2-95
4.0L, CV joint style Fr yoke, thru 11-1-95
4.0L, U-joint style Fr yoke
5.2L (8-318), from 11-2-95
5.2L (8-318), thru 11-1-95

1994 front DS options
AT, 8 cyl, CV joint style Fr yoke
AT, 8 cyl, U-joint style Fr yoke
MT (6 cyl)
AT, 6 cyl, CV joint
AT, 6 cyl, w/o CV joint


These are just a few listed. I have no problem swapping out the diff, even if I have to swap out both from a parts truck to save a few bucks I'll do it. But don't want to get hung up on some stupid driveshaft issue not having the right ones.
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Unread 10-17-2013, 10:40 AM   #10
PolkaPower
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Well all 4.0's came with 3.55's. Swapping to the 3.73 axles would be as simple as locating them from a 96+ V8, unbolting the old ones and bolting the new ones in. Your rear drive shaft may need to be a little shorter as the D44a is like an inch longer than the 35C. But you could just get the drive shaft from the donor vehicle. It would be an upgrade with gears and strength provided you found them in good condition.
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Unread 10-17-2013, 11:25 AM   #11
stageninja
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Quote:
Originally Posted by PolkaPower
Well all 4.0's came with 3.55's. Swapping to the 3.73 axles would be as simple as locating them from a 96+ V8, unbolting the old ones and bolting the new ones in. Your rear drive shaft may need to be a little shorter as the D44a is like an inch longer than the 35C. But you could just get the drive shaft from the donor vehicle. It would be an upgrade with gears and strength provided you found them in good condition.
What polka sez, take ds from donor & your golden. If donor has up country pkg. or is an orvis, take skid plates, tow hooks, springs & shocks.
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Unread 10-17-2013, 03:56 PM   #12
ZJLimited318
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Why does it have to be 96+?

Most parts vehicles I'm finding are 94-95
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Unread 10-17-2013, 04:25 PM   #13
PolkaPower
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Quote:
Originally Posted by ZJLimited318 View Post
Why does it have to be 96+?

Most parts vehicles I'm finding are 94-95
It doesn't have to be but 94-95 had the D35c in it which is a crappy axle. They used the D44a in the 96+ V8's. It's a much stronger axle but it has a couple draw backs. It can warp and eat up carrier bearings. It has an aluminum center section that can get bashed easy off road but with a truss and skid you can run 35's. I replaced my bearings at 129k miles. Been great and I have put over 10,000 miles on it since. The D35c is just really weak and I wouldn't pay any amount of money for one.

Ring and pinion from D44a on left and D35c on right.
screen-shot-2013-10-17-5.25.18-pm.jpg

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Unread 10-17-2013, 10:49 PM   #14
SLOspeed
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Quote:
Originally Posted by PolkaPower View Post
Well all 4.0's came with 3.55's.
Not true, 4.0 with tow package had 3.73's.
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Unread 10-17-2013, 10:56 PM   #15
SLOspeed
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Quote:
Originally Posted by PolkaPower View Post
Well all 4.0's came with 3.55's. Swapping to the 3.73 axles would be as simple as locating them from a 96+ V8, unbolting the old ones and bolting the new ones in. Your rear drive shaft may need to be a little shorter as the D44a is like an inch longer than the 35C. But you could just get the drive shaft from the donor vehicle. It would be an upgrade with gears and strength provided you found them in good condition.
96+, the D35 was used behind 6-cylinders which usually had the 242 transfer case with an an EXTERNAL slip yoke.

D44a was used behind the V8, which usually had a 249 transfer case with an INTERNAL slip yoke.

The difference between the internal and external slip yokes is, what? 4 inches in the driveshaft?

The difference between the d35 and d44a is around 2 inches in the driveshaft.

So, unless you can find a 96+ V8 with a 242, you'll have to have a custom driveshaft made to get the D44a to work.
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