4WD binding up (not sure where to start)

[Saicksss]

Got a 97 TJ earlier this year and have been tackling all kinds of issues to get it as a reliable driver, learning tons along the way from the forum. However, I just decided to test out the 4wd system and have now found yet another snag. Jeep runs and drives in 2wd perfectly, and shifts into 4hi very well, dash lights up and clicks in nicely no strange noises, ive adjusted the linkage and no change.

However, the jeep binds up within about a foot and starts to build a ton of pressure and wont move. tires start chirping and something is clearly wrong, its as if the brakes are being pressed. This is not the normal 4wd on pavement situation, the jeep will not move in a straight line even a few feet.

My first guess based on historical threads was a difference in gearing so today I jacked up all 4 corners and started testing some things, and the rear axle is geared for 3.73 as expected, I was told by the PO that the front should be the original 3.73 as well. Did a rotate test and found that the rear is indeed a 3.73, but kept getting a weird result on the front axle... it seemed to only be about 3 revolutions of the front driveline to turn the wheel 1 revolution

I put the TJ in 4hi and started it up, as youll see in the video below and the pass front wheel is clearly spinning faster than the rears (manually rotating the tires I found it was about 2.4revolutions for every 1 on the rear tires) and the front drivers side seems to be reacting very oddly. It only turns a little bit when you first turn the driveline and then just kind of stops (as seen in the manual driveline moving video)

I am a total newbie to 4wd systems and am utterly confused as to what is happening here (is this some sort of slip differential trickery?) or where to move to next on my diagnostics. is this potentially the drivers front axle is broken? would there be any reason to why a gear with a ratio of 3ish would be in the front?

It seems clear this is why there is a binding happening on the road when I try to go into 4wd but not sure where my next steps should be to get it working properly. Would like to get the 4wd sorted out before harsh canadian winter sets in

2 videos of the front wheels below

4wd engaged

hand turning the front DL

any ideas, tips, or explanations would be appreciated!

 

[Foxhound67]

I'd pull the front cover off the diff and see what's in there. You can try to count the teeth to determine the gear ratio. Strange that the drivers tire isn't turning, hard to tell in the video but it isn't still touching the ground is it?

 

[Foxhound67]

Maybe drivers side bearing bound up? Would explain why when you turn your DS only one tire spins, spiders in an open diff will do that

 

[billyp]

Agree to me sounds like different gear ratios in front and back.

 

[Saicksss]

So found the identifier tags and wire brushed them back to readability, front is a 3.07 and rear is a 3.73.... would it have come this way from factory or would gears have matched? it blows my mind that this would ever be purposely switched to have nonfunctional 4wd by someone

is this gear ratio diffference enough to explain the binding, and the only way to fix would be to either bump the front up to a 3.73 or the rear down to 3.07 correct?

and the drivers tire was free floating completely as well

 

[machoheadgames]

Open up the diff and confirm for sure, definitely sounds like mismatched gears to me. That the PO said the front "should" be the same 3.73 is a bit concerning, it would be odd for them to not know. I'm guessing they broke something and swapped any axle they could find in no matter what the ratio was.

 

[billyp]

So found the identifier tags and wire brushed them back to readability, front is a 3.07 and rear is a 3.73.... would it have come this way from factory or would gears have matched? it blows my mind that this would ever be purposely switched to have nonfunctional 4wd by someone

is this gear ratio diffference enough to explain the binding, and the only way to fix would be to either bump the front up to a 3.73 or the rear down to 3.07 correct?

and the drivers tire was free floating completely as well

Gears would have matched or 4 wheel drive would never have worked. If I had to guess, they broke one of the axles and switched out the entire assembly.

Yes that would explain the binding. Regear is only option.

Wondering if your axle shaft is broken on the free wheeling one. Only way to really tell us open the cover, turn the wheel and see if you can see anything turn inside.

 

[machoheadgames]

So found the identifier tags and wire brushed them back to readability, front is a 3.07 and rear is a 3.73.... would it have come this way from factory or would gears have matched? it blows my mind that this would ever be purposely switched to have nonfunctional 4wd by someone

is this gear ratio diffference enough to explain the binding, and the only way to fix would be to either bump the front up to a 3.73 or the rear down to 3.07 correct?

and the drivers tire was free floating completely as well

No, they would not have come factory like that. That is a huge difference in gear ratio, you'll have binding like that with any mismatched gear ratio though: 3.73&4.10, 3.73&3.55, etc.

As for the driver's side sitting there, I would want to open the diff and make sure the spider gears all function right and make sure that the driver side brake caliper isn't sticking, and also make sure that the left axle shaft isn't simply broken.

 

[Saicksss]

perfect thanks guys I will open up the diff next to inspect what is going on inside, and see what my options are to re-gear the front to match the rear 3.73s, and check if the front left axle shaft is broken

brakes are functional, had a seized caliper so that has been fixed recently with all new calipers and rotors and pads

appreciate it! regearing seems daunting but youtube and this forum have been great resources

 

[Foxhound67]

I just did mine, it's not too bad if you have the tools, plan to spend all day if you haven't done one before and ask questions, post pictures, etc

 

[Lou]

This happens when something in the front end blows up or the jeep is in an accident. PO puts in whatever axle they can get cheap and sells the jeep.

 

[OldBuzzard]

The front tires turning at different rates is pretty normal on an open diff. A little bit more drag on one side, say from a disk brake, will cause that side to turn slowly or not at all, and the other side to turn faster, or double speed. Put the passenger front tire on the ground so it can't turn, and the driver tire will probably spin at double speed. That's also how you check the gear ratio on an open diff. If you have a 3.07 diff, turning one tire with the other side blocked should give 6.14 turns of the driveshaft. You don't have to open the diff to get a pretty accurate ratio, if you mark the tire and driveshaft with chalk and each has a good reference point (on the floor, and a spot on the driveshaft referenced to the skid plate).

But yes, you will have to regear that front diff. I doubt you have anything broken, no horrible noises, just mismatched gears.

 

[Foxhound67]

This happens when something in the front end blows up or the jeep is in an accident. PO puts in whatever axle they can get cheap and sells the jeep.

Either that or they want to regear for tire size changes and only do the rear to save money because they "never use 4wd" and then it becomes someone elses problem

 

[97TJNM]

If it was me, I'd look for a 3.73 geared dana 30 entire front axle on Craigslist or Marketplace. If you look around a bit, you can probably find one cheaper than the cost of having a shop do the regear. And swapping in a front axle is a 1 day job, at worst. That said, if you're going to regear it yourself, that's probably the cheaper route.

 

[billyp]

If it was me, I'd look for a 3.73 geared dana 30 entire front axle on Craigslist or Marketplace. If you look around a bit, you can probably find one cheaper than the cost of having a shop do the regear. And swapping in a front axle is a 1 day job, at worst. That said, if you're going to regear it yourself, that's probably the cheaper route.

I think a used one is probably the best idea if you can find one. I'd bet you can find a used one cheaper than the cost of an overhaul kit and the tools needed (unless you've got the tools) to do a regear.

 

[Foxhound67]

Assuming you don't have the tools, in order of price lowest to highest:
1.Buying a used one and changing the fluid
2.Buying tools/parts to do it yourself
3.Paying a shop

 

[bucky]

So you did not find this issue when you test drove it before purchase? At least it can be fixed with some labor and a few bucks. Welcome to the TJ world.

 

[Saicksss]

Thanks for the suggestions everyone, waiting on a quote to get a local gear shop to re-gear and starting to hunt for a front axle to swap in, a used swap in will be ideal to not blow the bank on a junky side project car.

And no I was practically given the vehicle from the PO who needed it taken away that day... And I've been putting off testing out the 4x4 because I had a hunch something was going to create another headache and needed to keep the jeep driveable for the past few months while we waiting for our RAV4 to get made