Transfer Case Issues

[JohnVee]

I can't find any past threads with my exact problem so I'm asking for help here.

Background:
My truck is a 1978 (9/77) 40. I've had it 1.5 years. PO had MAF rebuild the transfer case about 8 years (~12,000 miles) ago - I have the receipt for this. It leaks about a drop of fluid from the speedo cable housing over a week of sitting still. No other fluid leaks of any kind.

Problem:
I first noticed a clicking sound and vibration coming from the T-case lever. Doesn't seem to happen at low speeds. Hard to hear over engine/exhaust noise over 20MPH, but it's there. I've now noticed that the lever gets very hot. After 10 miles you won't want to touch it for more than a 2 count.

Findings:
-Upon noticing my problem, I checked fluid level. T-case was about 1/4" below the fill hole. I drained the fluid. Looked fine. Very small amount of metal filings on the magnet (sorry that I forgot to take a pic). Refilled with Mobil 1 75W-90 to the fill hole. Problem still there.
-Our club had a show with other 40's coming from up to 25 miles of highway away. I checked the T-case levers of 3 of them as soon as they arrived - all were warm, but nothing like mine.
-Yes, the lever is definitely in 2WD, not 4WD, but there is about 1/8"-1/4" of wiggle room towards 2WD if I push firmly, but it immediately returns when I let go. And the noise and vibration are still present in that full-forward position.
-It shifts smoothly in and out of 2WD-4WD Hi-4WD Low while standing still.

I don't know if the problem exists in 4WD as I've been hesitant to drive it the distance to somewhere that wasn't paved. I have had to Reverse a few times in the past to get out of 4WD.

I appreciate any and all help that you guys can give.
-john

 

[DaveWest5150]

are your hubs locked?

 

[JohnVee]

^^^
No, they're not. I check on that pretty regularly.

--john

 

[miker]

Could it be because of an outside heat source? Perhaps the way the exhaust is routed on yours vs. others? Do you have an exhaust leak?

Is the transfercase itself getting as hot as the lever?

For the t-case shifter, there is a lower shift boot made of rubber and then the upper boot which is made of some kind of vinal material. If the lower boot is missing or torn, I could imagine that more heat could collect around the shifter lever.

Other places you may want to check out:
Transmission - is the heat coming from the trasmission? Maybe drain and inspect trans fluid.
Parking brake - is it dragging and creating heat?

I have no idea what might cause the clicking noise, maybe the e-brake? The clicking would bother me until I figured that out but may or may not be related to the heat.

 

[JohnVee]

Thanks, Mike. Pretty sure my exhaust isn't the issue as the lever temp wasn't that bad even in last summer's heat. No leaks in the exhaust for sure as of last week. I'll check your other suggestions this week. My "modern-car mechanic" changed my tranny fluid last month and said it looked fine.
--john

 

[Fast Eddy]

It leaks about a drop of fluid from the speedo cable housing over a week of sitting still.

Easy to fix. There's an o-ring inside the speedo insert cone thingee. You need a dental pick to get it out.

Problem:
I first noticed a clicking sound and vibration coming from the T-case lever. Doesn't seem to happen at low speeds. Hard to hear over engine/exhaust noise over 20MPH, but it's there. I've now noticed that the lever gets very hot. After 10 miles you won't want to touch it for more than a 2 count.

Hmm. The h-n-l shift fork could be worn weird. You could take out the seats, fuel tank cover, tranny tunnel, linkage and the top of the case to inspect it. It's kind of a PITA, but easier than dropping the case. If you do it, measure the thrust clearance between the high-range gear and the output shaft gear and the low-range gear and the output shaft gear.

If the thrust clearance to the low-range gear is about zero you might get the symptoms you are describing. Ever hear little screeches like a fan belt slipping?

Findings:
-Upon noticing my problem, I checked fluid level. T-case was about 1/4" below the fill hole. I drained the fluid. Looked fine. Very small amount of metal filings on the magnet (sorry that I forgot to take a pic). Refilled with Mobil 1 75W-90 to the fill hole. Problem still there.

The level was ok. Not sure I like Mobil 1 in this application, but it's not causing your problem.

the lever is definitely in 2WD, not 4WD, but there is about 1/8"-1/4" of wiggle room towards 2WD if I push firmly, but it immediately returns when I let go. And the noise and vibration are still present in that full-forward position.

Sounds normal. Does it vibrate differently when pushed forward? It is much more likely that a hot transfer case is the h-n-l shifter than the 2wd/4wd shifter.

I don't know if the problem exists in 4WD as I've been hesitant to drive it the distance to somewhere that wasn't paved.

Assuming you have locking hubs, you can put it in 4wd with the hubs unlocked at any time.

I have had to Reverse a few times in the past to get out of 4WD.

Totally normal.

 

[JohnVee]

Easy to fix. There's an o-ring inside the speedo insert cone thingee. You need a dental pick to get it out.

***I'm not worries bout this leak but will fix it soon since it looks so easy. Thanks for the tip.


Hmm. The h-n-l shift fork could be worn weird. You could take out the seats, fuel tank cover, tranny tunnel, linkage and the top of the case to inspect it. It's kind of a PITA, but easier than dropping the case. If you do it, measure the thrust clearance between the high-range gear and the output shaft gear and the low-range gear and the output shaft gear.

If the thrust clearance to the low-range gear is about zero you might get the symptoms you are describing. Ever hear little screeches like a fan belt slipping?

***I've not heard the sounds you describe. Would they be easily heard over the engine? I've worked heard to eliminate all other squeaks and rattles so I hope I would hear this if it were there.

The level was ok. Not sure I like Mobil 1 in this application, but it's not causing your problem.

***What do you like? M1 was all they had when I picked it up while the 'case was draining.

Sounds normal. Does it vibrate differently when pushed forward? It is much more likely that a hot transfer case is the h-n-l shifter than the 2wd/4wd shifter.

***No. Same vibration but the clicking noise becomes muted.


Assuming you have locking hubs, you can put it in 4wd with the hubs unlocked at any time.

***I was told the opposite (perhaps by the original manual?)...Can drive with hubs locked in 2WD, but never drive unlocked in 4WD.

****ALSO**** I forgot to mention that the clicking & vibration happen only when in gear. Coasting in neutral is fine. Revving engine while coasting in neutral is fine.

***My guess is that the heat is being generated by the friction that causes the clicking noise. I like your shift fork idea, Eddy. I'd love to open it up like you describe to check it out but it would all be Greek to me once I got to that point and I wonder if I'd be better off letting the pro's handle it instead of looking at it for a week or more trying to learn the inner working of a gearbox? I'm getting to be vehicle-handy but a gearbox seems intimidating. Thoughts?

***Transmission drain and fill is on the list for this week in the meantime.

***And thanks to everybody who's taken the time to read and respond to my post. It means a lot to have strangers willing to help.

--john
(now that I've previewed this post and see that the quotes didn't turn out as expected, I'll figure out how to do it right for the next time before typing so much.)