Transmission Assembly question

[cygnusx1]

I just finished replacing all the bearings and inspecting all the synchros in my 1982-83 five speed. I assembled it all in the vise, but without the case yet. The case is off so I can test it all. It shifts though the gears nicely on the bench, and all is smooth...except when I engage reverse. When I engage reverse, it is difficult to spin the input or output shafts by hand, there is quite a bit of drag. It spins with a wrench on the splines but it feels like there is a lot of drag. Possibly the 5th gear synchro dragging??

When in reverse, if I force the reverse shift rod 1/16" forward or backwards against the detent, the trans frees up perfectly. It's almost as if the ball detent for the reverse rod sets it slightly off from where it needs to be.

I went over and over the manual, and everything is assembled correctly, facing the proper directions. I tried the old and the new synchro with no difference. I have a hunch that when I install the case, it may free up, by the nature of aligning everything. Any ideas?

I don't remember if there is normally drag in reverse, with the case removed, or if it's unusual.

Only someone that has rebuilt one can probably answer this one.

[Zed Head]

Something off with the shift fork? Apparently they can bend or crack without breaking completely. The roll pins holding the fork on can shear also, maybe yours is halfway there. The fork might be directional also.

Have you seen duragg's rebuild opus on Hybridz? Might make you want to spend a little more time on it before you put it back in.

High RPM shifting dynamics - Drivetrain - HybridZ

[EuroDat]

I cant remember mine being harder to turn in reverse. It sounds like something is wrong with the selector.

My 280Z has a tranny out of a 280ZX and I changed all the bearings, syncros, nuts and such when I rebuilt it last year.

I posted photos of the selectors in a thread started by Leonv. You can see in there http://www.classiczcars.com/forums/engine-drivetrain-s30/49070-transmission-id-quiz.html

Chas

[Zed Head]

Is the gear assembly sticking out sideways or straight up?

Maybe the shafts are hanging from the gear set weight and causing misalignment.

It's pretty easy to stick the front case back on though and find out what will happen in use. I would do that anyway without sealant just to make sure things are right. I had one on and off several times and wished I hadn't been so confident with the sealant. Had to clean it up and start over. Don't forget to put it in to gear before putting the front case on or you'll probably lock it up when it goes in to two gears at once.

[cygnusx1]

The trans is horizontal so the shafts are cantilevered which is not ideal, but they turn nicely in all gears, including reverse when I force the R fork forward or backwards 1/16" or so.

I think I will do that (put the case on) because I can't think of anything else to try. I wish I had a second trans opened up right now to compare. The forks all move very nicely and all look straight on the bench. I had all the split pins in and out several times and they look good too. I will put the case on dry, and see what happens. Thanks for the tip on putting it in gear first. I had forgotten that one, since the last rebuild I did was about 25 years ago. .

My only concern would be that one of the center bearings is thinner/thicker than the original and is causing some misalignment that only manifests itself with reverse engaged....I doubt it, but that's all I can figure.

Edited April 5, 2013 by cygnusx1

[cygnusx1]

Nope, installing the case didn't loosen reverse. I added a 40 thousandths thick shim to the front of the R shift fork, to limit it's forward position when reverse is selected. The shim is tapped into the front bearing cover and acts as a shift rod stopper for R. With that shim in place reverse spins normally. I don't know why or what is off but I can't find it using the manual specs and instructions. It's probably a tolerance issue with something. We will see. I think it will be fine since all forward gears are fine and the selector hubs line up properly when gears are selected.