Tom400CFI

Bought my base '92 LT1 6 speed, 5 years ago @ 150k miles and it't been fantastic; all I've done besides drive it, road and drag track it, is change oil, an opti, and upgrade brakes and shocks.

After 5 years and 50k more miles on the car, it's time for some PM;
Trans fluid change
Rear diff fluid change
All U-joints
inspect wheel bearings
Intake manifold oil leak
front idle pulley replace (squeaking)
....Among other things.


The drive line joints I figured were due for two reasons;
1. they're age is unknown
2. I get some "clicking/snapping" noises when I start from a stop or back up (thinking rear axle joints), and my drive shaft vibrates a lot above 75 mph. Very annoying. Unfortunately, all the joints seem to be in fine shape. They're all "wet" still, needles look fine, no discernible play in them...I admit was I a little disappointed in what I found, given the symptoms.

I'm going to replace the U joints anyway since I have it all apart, but I don't think that was causing the "clicking/snapping" sound nor do I feel it was the cause of my drive shaft vibes.

First question is that IDK what is causing the clicking, if not the U-joints.

Second, What is the max spec for clearance of the slip yoke/tail shaft bushing? I can wiggle the slip yoke ~.5mm as measured off the C-beam w/a vernier caliper...no a great measurement, but the slop looks greater than the measurement I tool. I think it's too much but is there a spec for that?

kimmer

I also get a clicking noise off and on and my u joints are fine, I'll be watching this. [calipers?]

WVZR-1

I believe the condition of the slip-yoke would be an indicator of the condition of the extension bushing in the transmission extension. There's so little pinion angle on the C4 drive-shaft it would seem unusual for the bushing and slip-yoke to be damaged UNLESS there was a joint froze or really bad that created the interference that would wear the bushing. What was the condition of the slip-yoke? You mentioned being apart already. Maybe replace the extension bushing while you're there?

I'd say it's way past time for PM on the fluids so regardless of your choice I'd think there will be a dramatic difference in the feel of the ZF. Your last ZF service was 50K ago? Which fluid did you use then?

Idler could be as inexpensive as a bearing to fix.

Red 91

Search teflon washer for the clicking

esham

Tom400CFI

I'll take some pics but the slip yoke looks fine to me.

Previous fluids are unknown. Fluids that were in the car when I bought it. I know...I should have done this PM service THEN...but plan back then was to fix the car (didn't start), then sell it for $$. Unfortunately (for that plan), I liked the car too much...and the C6 got the boot instead.


Thanks for the reminder about the teflon bushings. I recall that now that it has been mentioned. There are none in my car...so that seems like the culprit.

WVZR-1

You would have seen slip-yoke wear I'd think.

You would have to remove the rear spindle/hub to check the condition of the washers. If you've not removed them then there's nothing to inspect. If you do the washers make sure you pay attention to the orientation of them. Washer part # 14076924. If you decide to do rear hub/bearing make sure you do the washers.

#48 in this image:

http://parts.nalleygmc.com/showAssem...=0&modelYear=0

Tom400CFI

I completely agree. There is wear on the slip yoke, but not much. I can measure up to .004" (0.1mm) in variation to the slip yoke. Here is a pic;


...and here is a vid or it in the trans, shaking it. I think I need to replace that tail shaft bushing.



Thanks for the parts break down. I have removed the shafts from the hubs. The entire rear drivetrain is currently out of the car, and apart. I do have washers in that location, but they are steel. I thought they were supposed to be plastic. Pics of one side's washer that I found in that location...

WVZR-1

Those are correct and the "Teflon" as it's reported is a surface treatment that I have to be honest can't be confirmed with a new one in your hand. Get two new anyway!

QCVette

Get two new anyway.

On my '94 I had one clicking. It was only from a stop and usually when I was turning left from a stop. The left rear washer was the problem. I replaced it and no more clicking.

The one that was clicking and several others since then that I have taken out all show some wear marks and there is no way I could tell by looking at them which ones might cause the clicking. For a few dollars, every time I work on the bearings or have it apart I put in a new one.

Good luck.

Tom400CFI

Will do then. Thanks.

Any consensus on the slip yoke? I think it's fine for further use w/a little polish....

WVZR-1

You could see if there's a shop in the area that does "hard chrome" and grinding. I would think if you're in any sort of a metropolitan area there could be. An industrial machine shop might supply a reference for you. The expense? Might be very economical. You could supply the service bushing with the slip-yoke to be used for sizing. That could be the other choice, buy a service bushing and check it for sizing to the yoke to decide. The bushing is inexpensive! You would use a TH400 bushing to check the sizing.

Bushings are actually sometimes honed to a spec after installation into the transmission extension. Some bushings are very tight. In your case that might be GOOD!

Tom400CFI

More good info. Thanks a bunch for the input.


Below is meaningless shots of the rear, before and after cleaning. I feel compelled to post b/c I think the C4 rear bits and pieces look so cool.

Here is what ~1/2 hr w/a pressure washer and some Eagle 1, Etching wheel cleaner can do....
Before:



After:

QCVette

Wow. Night and Day difference.

Did it take any scubbing with something or just the cleaner and pressure wash?

I like the way they came out. I don't want polished, but I want to clean and brighten up all the aluminum. This might be about what I am looking to do.

Great job and thanks for posting the pictures.

Tom400CFI

THanks!...and you're welcome.

No scrubbing at all. The Power washer basically made quick work of the caked on stuff to start with, getting it down to the exposed, but dull aluminum. After that, the power washer probably did little more than a garden hose would, as the Eagle 1 is so effective. It is an acid (I think hydrochloric acid) and it litereally eats away the top most layer of aluminum. So, you spray it on, let it sit for a few minutes, and then hose it off w/high pressure water, and wearing safety glasses. Stuff works awesome. The results you see were literally 1 application, ~3 minutes of sitting, then spraying off.

I agree w/you; my car is a driver so polishing is not going to happen...but CLEAN...that is happening.

Jay7199

Interesting.. my 93 6speed does the same click from a stop.. gona watch this thread.

QCVette

I took a look at the store. It is not hydrochloric, it is hydrofluoric acid.

That is one chemical that scares me. I used to work at a company that made medical ultrasound probes and used hydroflouric. It is NASTY stuff. It will cause severe damage to the eyes and/or respiratory system. It is rapidly absorbed through the skin and you may not immediately even know it. It will create a deep tissue and/or organ problems not just the surface of the skin.

A line quoted from the MSDS reads:
"Danger! Contains hydrofluoric acid."

My lab technique is not the greatest and on the car, I usually wind up getting stuff on me or scrubbing/wiping the surfaces so I get wet hands.

If you are using it, be careful. Use protective gloves, googles, and maybe a breather mask. I may still try it, but use extreme caution.

HlhnEast

You might consider getting new U joint straps and bolts as well. I have the same issue with a chirping and clicking and I have replaced the u joints and the rear bearing with a new "teflon" washer. I torqued the straps tight and within a week the clicking and chirping is back. I check the bolts and they have loosened up. I didnt use any blue loctite which I should have but I have purchased 2 new Spicer strap/bolt kits and they have loctite already on them. I have been dealing with a multitude of firing issues the last few weekends and havent gotten to them yet. Hopefully I will know this weekend if that is the issue.

I will post up if it solves my issue and will also keep an eye on this post to see what yall come up with.

Tom400CFI

Good input. Thanks for the additional idea/suggestion.


I agree. That is why I mentioned safety glasses above. I wore long sleeves, rubber gloves, and safety glasses. Getting the stuff on you is a no-no. But....it works.

QCVette

For the cleaner, I was thinking about trying it on some underhood aluminum, like the alternator, intake manifold, AC compressor, etc. I would like to brighten them up. Have you tried it on anything else?