Is it a transmission, transfercase, ujoint or rear diff problem?

stevemcgee99

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I've lost confidence in my diagnostic ability...

Now I have a squeaking noise from the back of the M1009, can hear it from inside. I thought it was the loose tire squeaking, but I tightened it down. The squeak seems to respond to speed. I'm wondering if my rear end is bad.


Occasionally there's a “Ping” shifting to D, or to R.
I have some vibration or grinding noise when coasting/decelerating around 45mph. Not really during acceleration.

Looks like transmission fluid leak, probably from the T-case.

Thought I might have a ujoint problem, now I think it’s worse. Can’t rotate or wiggle the drive shaft. Don't notice any deformation or anything that looks like bad ujoints I've had before. But I haven't taken them off yet.
 

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DeadParrot

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Check the brake shoes and pads. They often come with a metal finger designed to start making a squeaking/scratching noise when near EOL. A non finger equipped shoe could be starting to grind on the drum.

The Ping during shifting could simply be wear in the rear end letting things start to turn before the slack gets taken up. My 75 C10 has been doing that for a couple of decades. The ping survived a complete set of new u-joints.

The cost of a new gasket and a couple quarts of rear end oil make doing an inspection cheap compared to the cost of gear replacements.
 

cucvrus

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I would say definitely a rear driveshaft U Joint. Easy jack the rear axle up and support it. Put the transmission in neutral and check for slop and play. Look closely you should see millings and rust in the U joint area. Take the drive shaft off and check. Easy fix. But fix it before it is the front one and falls down and fits the road. New driveshaft after that. Good Luck.
 

cucvrus

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I looked at the pictures. I would also pull the transfer case drain plug and check the fluid level. If you have an over fill condition in the transfer case it could be the transmission rear seal leaking the transmission fluid into the transfer case. If you drain the over filled condition and check it another time in a month of driving and find the same condition and over filled that is the issue. I would reseal the front and rear transfer case seal while I was in there and grease the CV joint on the front drive shaft. That leak off the transfer case is doing a fine job of rustproofing and lubing the CV joint. Good Luck. Report your findings.
 
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stevemcgee99

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Noise got worse. During drive/acceleration, too. Got gear oil, gasket, RTV and new jack stands. :)

Will check out the ujoints and see if any Eaton chunks pour out the rear end after work tomorrow.
 

stevemcgee99

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I’ve got the ujoints replaced. Rear one was bad.

Seems like transfer case is leaking.
No fluid dripped from the filler hole.
Loosened the drain and some came out.

When I put my finger in the filler hole I don’t feel any fluid in there. Shouldn’t it be up to the hole?


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cucvrus

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Yes you should have it full enough to touch it with the first digit of the checking finger. Leaking transfer case is common. Replace both seals front and rear and try that. I had barbed wire wrapped in my driveshafts a few times. Last time I smelled the gear oil before I knew I was wrapped up again. It was wrapped up so tight it pulled the pinion seal out and luckily I was 2 miles from home. Take Care and check back. Good cordless impact is a plus to get the front yoke nut off. Good Luck.
 

Sharecropper

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Your leaky front transfer case seal may be more than the seal. You could have a scarred yoke shoulder to go along with a bad seal. I did a write-up on this a while back -

 

stevemcgee99

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Refilled and some leaked out until I put the slip shaft back in. Dripping through weep hole and also front output dust cover.

I believe my transmission is OK but the two t case output seals are bad.

Hopefully it can wait.


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Keith_J

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Does the transmission lose Dextron? You could have a rear transmission seal which is draining into the transfer case. This can overload the transfer case seals due to heat from the flood. That is why the fluid level for Dextron is 4 inches lower..the fill hole is designed for gear oil. When running, the gear oil is slung all over, reducing the level to reduce churn heating.
Nothing really changed with gearing or bearings when they changed to Dextron, it has excellent wear properties. It just flows much better and offers better fuel economy.
 

stevemcgee99

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The level was low. And definitely still leaking but I recently checked the transmission and added a pint or less. Will check again.

But seems like it’s the transfer case seals.

Thanks for the info on different oil levels.


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cucvrus

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I never seen gear oil in an aluminum transfer case of any make or model. The needle / thrust bearings in the aluminum cases are much different than the big ball bearings for lack of a better name in the old cast iron transfer cases. I don't remember what year the NP208 came standard on GM trucks but it always used Dexron ATF fluid. 800px-Dexron_(B)Dexron.jpg Good Luck. Change the seals and drive on. I clamp a good set of vise grips on the flange of the rear seal and hammer the vise grip hinge the seal comes out. The front one you need to get creative. Clean the areas thoroughly and tap a new seal in place. Tap not bang them in place.
 
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