1988 Manual Tranny issues

[system-f]

I am 99.9999% sure something is going on in the diff and am going to get another tranny tomorrow, but would also like your input.

The problem, a clicking noise that ONLY happens in slightly in 1st and 2nd, and loudly in 3rd, 4th, and 5th. This is NOT a CV shaft clicking noise and those are brand new (yes I have had faulty new CVs, but I highly doubt they are the problem)

1. Noise is directly related to wheel speed, NOT engine speed.

2. If I push in the clutch while moving the noise goes away OR if I give JUST enough throttle to keep the car coasting.

3. If I am moving at 40mph and I shift into 3rd, 4th or 5th WITHOUT changing speed the noise stays at the same frequency.

4. If I coast at 40mph in neutral and just barely push the shift into any gear you can hear the clicking noise as the syncros try to come into contact. Normally this would create no noise unless you somehow pushed hard enough to actually grind the syncros.

5. The transmission is out and 5th gear looks fine, input shaft has little to no play.

6. The clutch, pressure plate, and throw out bearing look and feel perfect. At the worse I have a little glazing on the flywheel and pressure plate.

7. the bushing in the flywheel seems to be within spec.

Ideas? My best guess is shot diff bearings or intermediate shaft bearings. Once the other transmission is secured I will tear this one down. Does any one know if it is even cost effect to rebuild these things and if so where can you get parts?

Thanks

[Dr_Snooz]

I'm not really understanding #4. Are you saying that the syncros are making the noise? Looking at #3, are you in the habit of going 40 mph in 2nd?

Usually these trannies go out by throwing 5th gear. Third gear can also develop shifting issues. The diffs are pretty rugged and it's not likely that. I seem to be able to find lots of trannies with blown mainshafts, but that's my burden and not anyone else's. I would be more likely to think you have a bad wheel bearing or possibly a CV installation issue. I'd also check the brakes.

The trannies are worth rebuilding. Rebuild kits are available from Transtar, but hard parts are hard to find. It's better to have a donor trans at hand. Of course, you run a fairly high risk of the same parts being bad in both your donor and core transmissions.

www.mantrans.com sells a very good rebuilt manual transmission so consider them if you don't want to do the rebuild yourself. I think they have access to a lot of hard parts too.

[system-f]

I have had plenty of bad CVs in any one of my 3 3gens and this is not a bad CV. I also have had the 5th gear failure in my last 3rd gen hatchback, 5th gear has already been inspected and looks great. Let me elaborate on the noise. It sounds like a gear grinding but not so violent.


I'm not really understanding #4. Are you saying that the syncros are making the noise?

I assume it is the syncros. If you are coasting at speed and the engine is at idle while the transmission in neutral the input shaft speed and the counter shaft speed are very different making shifting into a gear impossible. Normally if you try to push the transmission into gear in this case it would be impossible to go into gear but silent. In my case it is still impossible to go into gear but there is that noise.


Looking at #3, are you in the habit of going 40 mph in 2nd?

No, this is my daily driver/beater. I love this car. I should have said in 3rd gear at 40mph which is still spinning the engine, but not that bad.

Wheel bearings could be replaced, but not the issue...the noise goes away completely when power is removed from the drive train same with CVs. This noise actually sounds like a gear grind. One very important factor I failed to mention is that I did rear end someone in this car a week or two before the problem. This was a very minor accident but caused a host of other problems. The transmission case is in perfect order and has no impact damage that I can see, but I have no doubts that the accident set in motion the factors that are causing my problems. I will pull the transmission apart when the used one is secured. Do you know if the puller is required to seperate the case? Is there a generic couter part that will work? If not I will fab one.

Thank you for your help and response.

[carotman]

I don't think it's related to the input shaft since the noise doesn't change if you keep the same speed.

It could be related to the differential or intermediate shaft like you said.

Maybe a missing tooth in a gear.

[system-f]

I picked up another transmission at the junk yard for $165 that seems to be in great shape. 5th gear has very little wear.

[Dr_Snooz]

It's possible you damaged something inside the trans in the crash. I got a scrapper trans from the yard that I rebuilt. There was nothing to indicate that it was damaged, but it was. When I was done, it didn't want to shift into any gear and made a lot of noise. The mainshaft exploded in about 300 miles. I had to throw the whole thing out. You'll have to pull the thing apart to find out what's wrong but it's possible you won't see anything wrong.

For what it's worth, www.mantrans.com does really good work rebuilding MTs.

[system-f]

Once again thank you for the help. These are the kind of sources I need and will also help with my two 4x4 SUVs if they ever require drive train work.

I do see that the fuel injected and carbureted engines show different model number of manual transmissions, but I thought they were the same. Is there a gearing difference between fuel injected and carbureted?

[Dr_Snooz]

The final drive ratio is different, but they will bolt up the same.

[rdaniels]

system-f,

I'm experiencing the problem you describe above. Did you find/fix the cause?

rd