transmission squeak

[powderfinger]

I have a "squeaking" noise coming from the transmission on my 85 720, at least I am pretty sure it's the transmission. I am guessing it is a bad bearing inside the transmission but I am used to bearings grinding when they are bad. The squeak is always there until I push the clutch in and take the load off the transmission then it goes away. As the weeks go by it is getting louder. Has anyone else had this issue? I am hoping it isn't too much of a pain to replace.

 

I know where a complete truck is sitting that I can get for $200 that has a manual transmission and an engine in it, engine needs work. I was thinking about buying it and just swapping the transmissions but there is no guarantee that transmission is good either since it also has about $250,000 miles on it.

[datzenmike]

Why not remove the fill plug about half way up the side and check the oil level?????? Oil should be level with the hole. Top it up or even replace it if you don't know when it was done last. Should be GL-4 every 30K.

 

It does this in neutral with the clutch pedal up???

 

Does it do it while driving? Does it do it in every gear?

[wayno]

You need to quit driving it/running the engine and drop the transmission before a bearing comes out of the race and does major damage that is not easily repaired.

It sounds like you have a bad lower counter shaft/cluster gear bearing, this is a common issue with these transmissions, if you keep driving it you could possibly destroy the front cover and/or the bearing hole in the case which will make the front case useless as it likely already has the large counter shaft bearing, pull the transmission and fix it before it explodes/grenades.

Since you have kept driving it the gear oil will likely be a silver or black color or somewhere in between, if the noise goes away when you push in the clutch and put it in gear while the engine is running, then it likely also made some kind of noise while driving it, was it quieter in 4th gear?

 

[datzenmike]

Counter bearings carry the load in every gear but 'forth', which isn't really a gear at all but a straight through connection from engine to driveshaft. All other gears experience a side load that tries to thrust them apart. This is absorbed by the bearings, most notably, the front counter bearing. If quieter in 4th when accelerating / decelerating it's probably the counter. 

 

 

 

 

Bearings tend to sound lower frequency. A rumble, or growling sound. A 'squeak' is more like a dry U joint.

 

4 hours ago, powderfinger said:

  The squeak is always there until I push the clutch in and take the load off the transmission then it goes away. As the weeks go by it is getting louder.

  

If this is while in motion, under load, I would first check your U joints. Lets hope it is as this is a $20 fix.

[powderfinger]

Thanks for the quick replies. I changed the fluid with GL-4 about 2 months ago. It makes the noise in neutral and while driving. I can definitely hear it in neutral, 1st, 2nd, and pretty sure 3rd. After that the road and wind noise are loud enough that I can't really hear it. I guess it's possible that it doesn't do it in 4th and when in 5th it does but the other noises are louder.

[datzenmike]

OK does it make noises when stopped?

[powderfinger]

 

4 minutes ago, datzenmike said:

OK does it make noises when stopped?

 

yes

[datzenmike]

Rats, rule out the U joint.

[scooter]

probably counter gear bearing

[powderfinger]

yep, just got a great deal on a transmission jack which will make this much easier on my lift. I actually ended up getting two transmission jacks, one doesn't have the top plate. Neither were working because they didn't have any fluid in them so the guy sold them both to me for $25 :-) I got them home, put hydraulic fluid in them and they both work perfect!

 

 Hoping to pull the transmission this weekend.

[powderfinger]

Well, I got the transmission out but I can't for the life of me get the front cover off to be able to see the two front bearings. is there a trick to getting it off when it is stuck? I don't want to pry on it too much because it's aluminum.

 

I believe the main shaft bearing in front may be bad because there seems to be a little too much play in the front of the main shaft. I back bearing feels good and I believe the center bearing is okay as well. Can't tell if the counter shaft bearing is bad yet because I can't get to it.

[datzenmike]

 

 

Remove the 5 bolts and hammer on the clutch arm pivot ball through the clutch arm hole with a socket extension like above. It should loosen and pop off. Do NOT hammer on the nose that surrounds the splined input shaft.

 

Keep in mind that severely damaged counter bearings can destroy the cover plate inside making removal harder.

[powderfinger]

Thanks, that's exactly what I was doing. I guess I just didn't hit it hard enough. I don't think the bearings are severely damaged. I think the transmission would have sounded worse if it was that bad. Guess I'll find out soon enough.

[Stoffregen Motorsports]

I had a similar noise in a Datsun trans once, and at the very moment I started hearing the noise, I realized with horror that I forgot to fill the trans with fluid. It had a tiny bit in it and I just plain forgot to add more.

 

I got it home in time (before it blew up) and filled it up with gear oil, then took it out for a test drive. The noise was still there, but then something strange happened, the noise started to go away. After that, I put about 10K more miles on it before I sold the truck.

 

Near as I can tell, with a little help from reading, the heat of the unlubricated bearings caused what little oil was in there to "coke" onto the bearing races. By adding oil and running it, the coke film quickly wore off and everything went back to normal.

[powderfinger]

Finally got it apart after work today. Everything looks really good, the reverse gear has some wear on the front corner of the gears which I expected on a 35 year old transmission but other than that everything looks great. How much side to side play should the front shaft have when the front bell housing/cover is still on the transmission? I thought the main front bearing was bad when I first got the transmission out of the truck because there was a little side to side movement of the front shaft but now that everything is apart that bearing feels good and it wasn't exactly a press fit of that bearing in the front cover. It slid out easily once I separated the cover from the middle part of the transmission.

 

The countershaft bearing doesn't feel like it is worn too bad but I do hear/feel something that isn't quite right, it isn't perfectly smooth when I hold it and turn it.

 

I will probably go ahead and replace both while I have it apart to be safe. I haven't inspected the bearing on the tail side yet. 

Quote

 

 

[datzenmike]

Once unsupported by the front cover the main and counter shafts will move very slightly, relative to each other. The bearings must spin smoothly. If you think you can feel anything at all it should be replaced. There are two bearings in the adapter plate that hold the main and counter shafts and two larger bearings one on the end of the counter shaft that fits into the rear case and one about half way along the mainshaft also supported by the rear case. The rear two you can spin by hand and examine but the two buried in the adapter plate are harder to examine, mostly visual for damage.

[powderfinger]

Thanks, I am hoping the two in the adapter plate are fine. I don't visually see anything wrong and I don't feel anything when spinning the shaft. I will check the two rear bearings tonight if I get home in time and then get any that I need ordered so I can get the truck back on the road to keep the miles off my big truck.

[Stoffregen Motorsports]

The best way to inspect a bearing is to spin it. I use compressed air and some WD40. Spin them and listen for noise. If any noise is present, the bearing is either dirty or toast.

 

***Obvious disclaimer goes with using air to spin a bearing***

[alexg89]

just my 2cents of chiming in

Ive had multiple trans go bad (hoping not by my doing but because they are sourced used) because the cages on the bearings in the center section let go 

They will make all kinds of racket in every gear other then 4th.. squeaking, rattling, few have locked up on me .. its been a nightmare 

This was one of many 

[Crashtd420]

Same here.... center bearing was split in half.... only once I took the bellhousings off did I realize it.....

Wasn't planning on a rebuild just a housing swap.....

 

My bearing. ...

 

 

 

 

[datzenmike]

I found a Z22 5 speed at the wreckers. The oil that poured out looked like silver paint and the drain bung had a couple of BBs on it. Have seen parts if the bearing race before too. It's that riveted metal strip that wraps around the balls.

[bottomwatcher]

Looks familiar. Mine have always been the front countershaft ballbearing. The rear is a roller bearing definitely stronger but I guess can't take much for thrust loads. I am guessing that is why they use the ball bearings for the front and center?

[datzenmike]

Curious. All the 71Bs I have seen are ball bearing.

 

 

This is a 71C and it does have a roller bearing on the rear counter shaft

 

 

[bottomwatcher]

The reason I was thinking about this was I had my spare 71C apart last week considering a rebuild. Everything looked pristine so I sealed it back up. Looking at the manual showed roller bearings on the rear of the countershaft of both the B and C but I don't remember them in the B. I do have an old B I can check next week. This got me curious.

[datzenmike]

What manual? They may have just used a single picture for both B and C. Pretty sure the B does not have rollers.