Eaton / Detroit locker seems like it's unlocking at 55 mph

CherokeeKid

CherokeeKid

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I've searched but not found an existing thread with anyone experiencing the same issue as me... Hopefully I've not overlooked it.

My 03 TJ X has a detroit in the rear Dana 35 with super 35 axles and 4.56 gears. Generally behaves as expected, occasional noise on tight turns with non-neutral throttle input, a clank when taking off in first after reversing once in a blue moon, etc.

However, at ~55mph+ it seems like it's unlocking, on average once every few miles for a split second. When driving above 55, I often hear a popping sound from the rear end and the jeep kind of jerks to one side, generally the drivers side like its unlocking and only transferring power to the passenger rear wheel for a split second. The jerk isn't violent, feels more like a gust of wind. Tire tread & pressure is even, same sized tires all around, weight transfer is even, etc.

Once more, Harmon Four Wheel Drive in Tulsa (seems to be a reputable shop) recently troubleshot the issue and couldn't find any reason for this behavior. They tore the locker apart and reinstalled with new bearings and seals while everything was apart and setup the rear end again. Their only suggestion is to go to something selectable or LSD. I've never heard of a properly functioning Detroit, lunchbox, TrueTrac, etc. behaving this way.

Any thoughts?
 
Was anything done to it prior to it starting to act up? Change to new tires? Rim? Brake? Axle shafts? Anything at all that has to do with the rear axle? How many miles did you have on it before it started to act up? Any wheeling trips? How long has the Super35 kit been in the vehicle?
To add to what Jerry asked, measure the height of each rear tire.
 
Wildman said:
Was anything done to it prior to it starting to act up? Change to new tires? Rim? Brake? Axle shafts? Anything at all that has to do with the rear axle? How many miles did you have on it before it started to act up? Any wheeling trips? How long has the Super35 kit been in the vehicle?
To add to what Jerry asked, measure the height of each rear tire.
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Both rear tires are and have been at 25 psig, I've checked repeatedly.
Both rear tires are 31.5 inches exactly, I just measured to confirm.

As for when this started, I'm not sure...

Some background... Purchased Jeep from second owner in November 2020. Original owner had Detroit installed in rear, lunchbox in front, 4.56 gears, SLE, double Cardan driveshafts front and rear, tummy tuck with motor mount and body lift. Second owner got this Jeep around 2014 with 44K on the odometer. I purchased it in Nov. 2020 with 99K miles. Apparently this issue has been present ever since the second owner got it.
Axle shafts(TEN Factory super 35) were replaced under warranty when Harmon Four Wheel Drive inspected/rebuilt the rear diff. as some pitting was observed on the axles.
 
Okay not knowing when it might have started sucks....

When Harmon 4WD inspected the locker and the shafts did they also check to make sure that housing is straight? I have no idea if a bent axle housing could cause this issue but just throwing ideas out there.

Have you or the 4WD shop contacted Eaton about the problem? They might have a better idea of what to look for.
 
Wildman said:
Okay not knowing when it might have started sucks....

When Harmon 4WD inspected the locker and the shafts did they also check to make sure that housing is straight? I have no idea if a bent axle housing could cause this issue but just throwing ideas out there.

Have you or the 4WD shop contacted Eaton about the problem? They might have a better idea of what to look for.
Click to expand...
Wildman,
Thank you, Harmon did contact Eaton about spring load/bearing pre-load and Eaton essentially washed their hands of it. Perhaps I should call them directly.

As for bent axle housing, it seems to not be the case based upon my magnetic
angle finder I used before buying this Jeep.
 
CherokeeKid said:
Wildman,
Thank you, Harmon did contact Eaton about spring load/bearing pre-load and Eaton essentially washed their hands of it. Perhaps I should call them directly.

As for bent axle housing, it seems to not be the case based upon my magnetic
angle finder I used before buying this Jeep.
Click to expand...

Okay. The bent housing was just a shot in the dark because I knew someone who kept having issues with their ARB and it turned out to be a bent housing.

Yes if you called them and explained the issue maybe they can point you in a direction to help.
 
Any chance your transfer linkage might allow 4hi to partially catch a bit?
Try pulling the front d.s. and replicate the problem. Then try pulling rear shaft, run in 4hi and duplicate.
Like Wildman, just spitballing here. But if it came with this issue it could just be acting like the rear axle.
 
Have you looked inside the diff? Turned the gears and checked the teeth?
 
Control arms are factory, no adjustment. I did take a look at upper and lower bushings and arms, bushings don't seem worm out and arms aren't bent. Wheelbase measures the same on both sides(within about 1/8").

I did check the transfer case shifter, its aftermarket. In 2wd, the shifter is contacting the plastic console. It feels fully engaged though, I disconnected linkage to confirm. The trans. case shift arm won't engage 2wd anymore than it does when connected to linkage. I plan to try some stuff anyways to see if I can make it worse/better. I'll drive on highway in 4hi, drive without front driveshaft, drive without rear driveshaft.

I personally have not had the diff. covers off yet. I'm guessing Harmon would not have put it back together if there was a problem with the ring or pinion, I'll call them to ask what they recall.

Thanks for everyone's suggestions thus far, I do appreciate it!
 
CherokeeKid said:
Control arms are factory, no adjustment. I did take a look at upper and lower bushings and arms, bushings don't seem worm out and arms aren't bent. Wheelbase measures the same on both sides(within about 1/8").

I did check the transfer case shifter, its aftermarket. In 2wd, the shifter is contacting the plastic console. It feels fully engaged though, I disconnected linkage to confirm. The trans. case shift arm won't engage 2wd anymore than it does when connected to linkage. I plan to try some stuff anyways to see if I can make it worse/better. I'll drive on highway in 4hi, drive without front driveshaft, drive without rear driveshaft.

I personally have not had the diff. covers off yet. I'm guessing Harmon would not have put it back together if there was a problem with the ring or pinion, I'll call them to ask what they recall.

Thanks for everyone's suggestions thus far, I do appreciate it!
Click to expand...
And you verified your left/right side tire pressures are identical?
 
Jerry Bransford said:
And you verified your left/right side tire pressures are identical?
Click to expand...
Yes sir, digital and analog tire pressure gauges check out at 25 psig both left and right, front and rear.
One thing I tried today was driving on the highway in 4hi... and didn't experience any of the unlocking noise or side to side jerk... Not exactly sure what this means. Plan to try to narrow down the issue. Though sound seems like its coming from the rear, I'll remove front driveshaft and drive it then remove rear driveshaft and drive it and see how it acts.
 
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You didn't notice the clunk because the drivetrain was bound up from being in 4Hi on the highway. The TJ's part-time t-case wasn't designed to be driven in 4x4 on pavement.
 
Jerry Bransford said:
You didn't notice the clunk because the drivetrain was bound up from being in 4Hi on the highway. The TJ's part-time t-case wasn't designed to be driven in 4x4 on pavement.
Click to expand...
I've no idea what's causing what seems to be an unlocking issue when driving straight on the highway above 55 mph in 2hi, what I know is that the issue isn't observed when driving straight on the highway above 55 mph in 4hi regardless of the original design intent.
I was under the impression that with identical front and rear gear-sets, there should be no binding.
What does this suggest? Should I now look into the front diff? Look into unlocking/locking hubs? Trying to understand how the binding would essentially fix the problem and would like to replicate binding in 4hi while in 2hi.
 
CherokeeKid said:
I've no idea what's causing what seems to be an unlocking issue when driving straight on the highway above 55 mph in 2hi, what I know is that the issue isn't observed when driving straight on the highway above 55 mph in 4hi regardless of the original design intent.
I was under the impression that with identical front and rear gear-sets, there should be no binding.
What does this suggest? Should I now look into the front diff? Look into unlocking/locking hubs? Trying to understand how the binding would essentially fix the problem and would like to replicate binding in 4hi while in 2hi
Click to expand...
 
If I come across as an ass, its not my intention. Very frustrated with my Jeep right now. I appreciate everyone's input and especially yours Jerry. Just hope to figure this out...
 
CherokeeKid said:
... I was under the impression that with identical front and rear gear-sets, there should be no binding.
Click to expand...
They're not identical, the Wrangler's front and rear ratios are .01 apart, as in 4.55/4.56, 3.73/3.74, 4.10/4.11, etc. due to the different ring gear diameters. Only the Rubicon f/r ratios match due to their matching f/r Dana 44 axles.

And even if they match there will still be binding aka windup since the front tires rotate slightly faster than the rears when driving on curves and turns.
 
Jerry Bransford said:
They're not identical, the Wrangler's front and rear ratios are .01 apart, as in 4.55/4.56, 3.73/3.74, 4.10/4.11, etc. due to the different ring gear diameters. Only the Rubicon f/r ratios match due to their matching f/r Dana 44 axles.

And even if they match there will still be binding aka windup since the front tires rotate slightly faster than the rears when driving on curves and turns.
Click to expand...
Gotcha, thanks Jerry. I'll look into this to see if it helps explain why I don't have this diff. unlocking issue when running in 4hi. Maybe the binding helps load up the rear diff. or something keeping it from unlocking.
Or maybe it has nothing to do with that, going to pull driveshafts next and see what happens.
 
Is this happening with neutral throttle or more when starting to accelerate or decelerate? I had a Detroit Locker for years in my previous daily driver TJ that spent a lot of time on the highway.
 
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