4wd binding in High, not binding in Low

[Herb31]

Hi all. I'm new to this forum.

On gravel, going straight, I shift into 4 high and the CJ feels like the brakes are on. It will move forward, but it is very jerky.

I shift into 4 low and it seems to work fine.

Could it be that I have mismatched gear ratios front and back? I have checked the Tcase linkage and it appears to be solid and not worn.

 

[CJim7]

Hmm...
Mismatched gears would cause the problem you describe...but that would also show up when in 4-lo.

Im thinking there's something going on in your Transfer Case when in 4-hi

 

[Old Dog]

Hmm...
Mismatched gears would cause the problem you describe...but that would also show up when in 4-lo.

Im thinking there's something going on in your Transfer Case when in 4-hi

I would pull the diff. covers off and check the gear ratios just to be sure. They will thank you for the fresh oil anyway.

 

[BajaEdition]

I agree about the ratios would be the same or it shows up nomatter what gear you are in
but as old dog says, change the diff oil anyway to check
sound to me like you have Tcase issues, what T case do you have?

 

[BusaDave9]

Try 4x4 high but with the hubs unlocked.
Also try 4x2 but with the hubs locked.

If that works fine then it could be the TCase is trying to turn the front axles a different speed than the rear.
I am wondering if the front is stuck in low. You checked the Transfer Case linkage but it could be the shift fork for the front came loose inside the TCase.

I assume you don't have twin sticks installed. If you do we can test the front drive separately from the rear.

 

[Herb31]

I do not have twin sticks. I will test as you say, 4X4 with the hubs unlocked. I have tried 4X2 with the hubs locked..it works fine. I am also going to jack her up this weekend and spin the wheels and count axle rotations to determine the gears front and back. I figure that will be easier than removing the diff covers, for now anyway. I will report what I find. Thank you all very much for the help.

I have the Dana 20 Tcase, single shifter.

 

[BusaDave9]

Check this out:
http://www.jeep-cj.com/articles/powertrain-3/how-to-tell-what-gear-ratio-is-in-your-cj-34/
But I think it would be very unlikely any mechanic would regear only one axle. If you can replace or regear axles you wouldn't be making that kind of a screw up.

 

[CJim7]

Check this out:
http://www.jeep-cj.com/articles/powertrain-3/how-to-tell-what-gear-ratio-is-in-your-cj-34/
But I think it would be very unlikely any mechanic would regear only one axle. If you can replace or regear axles you wouldn't be making that kind of a screw up.

I've seen it LOTS of times Dave....somebody takes a rig into a shop to replace blown R&P, shop doesnt have the right gears in stock, customer is in a hurry...assuring the shop and himself he will "eventually" regear the front to match, shop installs the gears on hand...owner sells rig without dealing with the front axle.

I still dont think that's the problem...once again, that issue would raise it's ugly head in 4-lo also.

Another thing to consider is worn front axle ujoints, bearings, and front driveshaft components (slipyoke, unoints). These may not show up at lower speeds (4-lo) but may show up at higher speeds when in 4-hi. Maybe.

 

[Herb31]

I spun the axles today and confirmed it....front axle rotated 3 1/2 times with two tire rotations. Rear axle rotated 2 3/4 times with two turns of the tire.

Dagnabbit!

So, I guess it would be best to re-gear the rear to match the front, eh?

Any idea how much this project is gonna cost me?

 

[BajaEdition]

do a full rebuild when you regear
around 1000 to1300
but then it is done right

owning a CJ is not cheap, you are dealing with 25 plus years of someone else owning the Jeep and doing half repairs, you are dealing with old technology and it has been bruised offroad
you are dealing with wore out parts

but the rewards are great.

 

[CJim7]

I spun the axles today and confirmed it....front axle rotated 3 1/2 times with two tire rotations. Rear axle rotated 2 3/4 times with two turns of the tire.

Dagnabbit!

So, I guess it would be best to re-gear the rear to match the front, eh?

Any idea how much this project is gonna cost me?

sounds like the front is 3.55 ratio and the rear is 2.73.

The reason it didnt buck around in 4-low is the front was naturally pulling as the rear was "drug" along slightly. This is a better situation then the rear pushing and the front resisting...as far as binding goes. My point however, is at low speeds, the ratio difference is tight.

When you went to 4-hi, the ratio was further seperated by tire speed and therefor more noticeable

 

[BusaDave9]

Now you have to decide what axle to regear.

sounds like the front is 3.55 ratio and the rear is 2.73.

What tire size do you run?
How's the RPM on the highway?

 

[Herb31]

Now you have to decide what axle to regear.

What tire size do you run?
How's the RPM on the highway?

32" tires. Truck doesn't sweat 75mph at all on the highway...I don't know the RPMs, but it sure isn't working hard.

 

[BusaDave9]

32" tires. Truck doesn't sweat 75mph at all on the highway...I don't know the RPMs, but it sure isn't working hard.

You would have very low RPMs with that gearing. I would regear the rear to match the front. That would increase the RPM on the highway but that would be good. Better acceleration. This would also give you the chance to install a locker or Limited slip.

2.73 gears are off the charts tall. Shoot for the green area. The numbers in the middle are RPM at 60 mph.
3.55 is still slightly tall. (that's what yellow means)

 

[1986cj7]

sounds like the front is 3.55 ratio and the rear is 2.73.

The reason it didnt buck around in 4-low is the front was naturally pulling as the rear was "drug" along slightly. This is a better situation then the rear pushing and the front resisting...as far as binding goes. My point however, is at low speeds, the ratio difference is tight.

When you went to 4-hi, the ratio was further seperated by tire speed and therefor more noticeable

Yes the best situation would be to have the front tires pulling slightly more then the rear. But when I was regearing I had trouble to find a gearing setup that would alow the front to pull slightly more then the front without being to far apart and causing the binding and trouble you are having. In most 4wd tractors this is the case the front is geared a little higher to cause the front to pull slightly more then the rear. But most gear sets or to far apart to be usefull aplication.

 

[CJim7]

I spun the axles today and confirmed it....front axle rotated 3 1/2 times with two tire rotations. Rear axle rotated 2 3/4 times with two turns of the tire.

Dagnabbit!

So, I guess it would be best to re-gear the rear to match the front, eh?

Any idea how much this project is gonna cost me?

sounds like the front is 3.55 ratio and the rear is 2.73.

The reason it didnt buck around in 4-low is the front was naturally pulling as the rear was "drug" along slightly. This is a better situation then the rear pushing and the front resisting...as far as binding goes. My point however, is at low speeds, the ratio difference is tight.

When you went to 4-hi, the ratio was further seperated by tire speed and therefor more noticeable

Wait a minute. Im wrong here. According to what you are saying, the front is turning faster then the rear. Therefore, the front is higher geared (numerically lower) then the rear. The 3.55 front and 2.73 rear I quoted earlier would result in less tire spin up front and more in the rear.

With an open differential, you have to rotate the tire twice and divide that by pinion rotation.....so according to your investigating, you do have a 3.55 front and a 2.73 rear.

Where I was wrong, is that the rear is effectively pushing the front....not the other way around as I stated

You are experiencing severe bind in the Transfer Case . Worse then if the front were higher geared and creating pull, the pushing action of the rear axle will tear up the case.

 

[Herb31]

Worse then if the front were higher geared and creating pull, the pushing action of the rear axle will tear up the case.

Yeah, I really hope I haven't buggered up the TCase while trying to sort out this problem.