Please Explain This! - 4wd Issue

[JaysJeep]

Front tire after 1 rotation of the rear

 

[HOrnbrod]

That's nice - but you already knew the ratios were different. You still don't know what the actual ratios are.

 

But I'm having an issue that I can't explain. When it's in 2wd, it goes great. But when I put it in 4wd, the rear driver side wheel seems to move slower than the rest, and just skids along. It almost looks like it is trying to go backwards.

 

If it were mine, I'd like to eyeball the gears after that too, especially on a "new to you" truck.............

[Jeepman]

If it were mine, I'd like to eyeball the gears after that too, especially on a "new to you" truck.............

BINGO.....

 

Diff fluid and RTV are Cheap enough, and getting the actual ratio's if different will be

better then guessing what the ratio's are as the turn the pinion count is not all that accurate...

[DirtyComanche]

Honestly, at that point the whole driveline is rather suspect.  If the rear is a D35, I'd pull the cover on the D30 front and go looking for a new (better) rear to match the front...  Might want to check all your ujoints and the tcase chain while you're at it.

[JaysJeep]

A 4.0 auto would have come from the factory with 3.55 in front and rear.  A manual would have come with a 3.07.

 

It looks like you one of each.

 

Math: (3.55-3.07)/3.55= 13.5%

 

That is close to 1/8th (12.5%)

 

Was the truck originally 4wd?  Is the front axle CAD or non-CAD?  (Is there a "box" on the passenger side with vacuum lines connected? Yes=CAD, No=non-CAD)

 

Was it originally auto? manual? Swapping from one to the other along with one axle may be the problem.

 

 

 

Edit: All 4wd MJs came with the CAD front axles.

 

I looked up the VIN. It is originally 4wd an originally manual. Still in that condition. 

[gogmorgo]

My guess is the existing D35 got lunched and the first one found to replace it went in just to get it back on the road. Imma say 3.55's in the back.

But that's just another guess.

[DirtyComanche]

My guess is the existing D35 got lunched and the first one found to replace it went in just to get it back on the road. Imma say 3.55's in the back.

But that's just another guess.

 

Most likely.  Finding a Comanche rear axle can be a bit of a challenge if you're sticking to conventional means.  "Close enough" or "We'll swap the front later" or just pure ignorance is likely the rest of it.

[gogmorgo]

And if that's the case, it's good news cause 3.55 D30's are a dime a dozen.

[yxmj]

Or the PO did not take the 5 minutes to take the diff cover off and find out for sure what the ratio was....speculated it was x.xx:1 and put in one guessing it was the same.....but that would just be a guess on my part....