nomind

Okay, so my 85 has a T5 swap in it. It got stuck in third gear, I pulled it down, and found the keys for the 3/4 syncro were toast (7 pieces). Replaced the keys, put it back in, and as soon as I hit third gear, I heard them come out again, and it was stuck in third again. Anybody got any suggestions? I kinda need to get this thing back on the road again quickly. Would replacing the whole 3/4 syncro assembly maybe help?

jmd

iTrader: (4)

They shouldn't drop out with new retainer springs and properly set clearances.

Overshifting the synchro (farther than it needs to go into gear; happens sometimes from abusive shifting) can cause it. A "loose" setup mainshaft to maindrive clearance could cause it.

Usually the keys and retainer springs wear much quicker than the surfaces of the synchro hub & slider that could potentially cause the keys to drop out.

85Z28NOS

iTrader: (2)

It sounds like the retaining rings arent very good anymore. you can get them at a decent price but might as well replace the syncros too. I to had busted my keys. I opted to rebuild my trans since I had to take it apart to get to them. I did how ever go with some billet keys they make for the 5.0 crowd that are alot stronger. Didnt have any more trouble with mine to date.

sofakingdom

iTrader: (1)

The reason they're coming apart, IS NOT the "synchro" at all.

There's no such thing as "overshifting"; the sleeve slides over the ring and hub until it hits the back side of the gear, where it stops.

The reason they keep coming out is because there's too much space between the clutch gear (has the 4th stuff on it) and the mainshaft (has the sleeve and 3rd gear on it).

The reason there's too much space is because the preload that the clutch gear bearing is supposed to be putting on the clutch gear, pressing on the thrust bearing between it and the mainshaft, has gone away.

The reason the preload is gone is because the whole front of the transmission is being subjected to forces it wasn't designed for.

The reason there are unintended side loads and whatever else on the clutch gear, is because the pilot is unsupported.

IOW, you don't have a transmission "problem"; you have a transmission "symptom", wherein the actual problem resides outside the transmission but the transmission is the part that gets destroyed by it.

When you replaced the pilot as you put it back into the car, did you install a bushing, or a bearing?

nomind

Pilot bushing wasn't replaced, as it only has about 10k on it. If it is something that I screwed up with the initial install, which is very possible, what do I need to do to correct the underlying cause? Just replace the pilot bushing correctly, and repair the trans?

sofakingdom

iTrader: (1)

You need to find out why the preload between the clutch gear and mainshaft is gone; repair that damage; and restore the preload.

A wiped-out or non-existent pilot bushing is the most common cause. But if in fact that's what the root cause is of the trans being destroyed, then you have to (a) fix whatever is trashed in the trans; and also (b) put a new pilot in the crank. One or the other by itself doesn't constitute a solution.

Doesn't matter how many or few miles ago it was replaced. The trans does not look out at a gaping hole and say "well it's only gone 10,000 inches since installation so I'm good with the end of my shaft slinging around loose in a quarter inch of space anyway". Either it fits or it doesn't. If it fits right and has 200,000 miles on it, it's good. If it's loose and just got put in yesterday, it's bad.

nomind

I appreciate the advice, it was exactly what I was looking for. I'm picking up the parts to repair the trans, shims to reset the preload on the input shaft, and a new pilot bushing. I really hope it goes better this time, cause I really need to have the car back on the road.

sofakingdom

iTrader: (1)

If you have it that far tore down, I'd suggest going on ahead and "rebuilding" it completely; which is, replace all the wear parts, specifically, bearings. No sense in accidentally leaving something that's wore out, un-renewed.

The "kit" has all the bearings, seals, O-rings, etc.; as well as the shims for the clutch gear bearing. You can get that from 5speeds.com (betcha never woulda thought of THAT URL), Hanlon, maybe a couple of other places.

You can download the complete service manual from Tremec.

nomind

I have the complete manual. Luckily, there is a shop here that has everything I need. I'm picking up seals, bearings, and the brass rings, along with said parts today.

nomind

Thanks again. Pulled it out, replaced the parts, reset the preload on the input shaft, replaced the pilot bushing, and I've put 100 miles on it in 3 days.

sofakingdom

iTrader: (1)

What was actually "bad"?

nomind

I think it was the preload on the transmission. The input shaft had some play in it when I pulled the trans out.