Landseer

Just opened-up my 83 5 speed gearbox. ( my car is 84, this box appears to have been substituted along the way )

This box shifts very well, gear to gear.

Gearbox has been popping out of 4th on decel since I bought the car in '07. I can hold it in fourth on decel, but it really wants to jump out, on abrupt decel, almost with enough force to self-select 5th.

Visual inspection shows nice, complete and full dogteeth on all gears. And I think minor nick-tracks around the center of what I think are second and fifth. Rest looks good, cursory look. (other than chipped reverse gear and broken reverse lockout) Overall, much better condition than I feared, but consistent with its good-shifting character in general. Might be a rebuilt box.

Each gear is selectable by hand. The appropriate shift fork and selector rods kind of lock-in on the gear and you can't really wiggle shift fork, fore/aft, when that gear is engaged. Except for fourth. In fourth, the 4/5 selector fork and shaft, together, have a bit of motion fore/aft. Its clearly in fourth gear, but the rod and selector are not locked there as firmly for fifth. Thoughts?

Why is this? How can I fix it? What holds it in fifth so much more firmly. (EDIT --- Bad observation on my part. Fork/shaft also has movement when 5th is selected. Other selector forks don't behave like this one.

The second and third pictures, below, shows the parts I'm talking about. They might not be in fourth in this particular picture, but you get the idea.

Who's got some experience with the innards of these babies?

Landseer

Bump. Gonna need some help on this one guys.

DR

Here is a pic that may help...fixed this one with the same 4th pop out problem.

Landseer

Thank you, DR, for posting.

BTW, your guy, Dr. Crumley, mentioned this at SITM and took me down this path to pulling the trans out this weekend. Many thanks to both of you.

My box is the earlier one, with the roll pins instead of locator bolts.

But I think together we have solved this. It definitely is unwanted / imprecise movement of the shift fork that is causing 4th rejection.

I removed, just now, the detent plug for the 4/5 shaft. Guess what! Had a plug ( #1 in picture below , a sealing ring, but no spring and no detent!
Stuck my allen wrench up the hole and can feel the divot on the shaft. Nothing in the hole, though. (EDIT --- shouldn't be a detent --- WSM shows this is an access channel, detent is loaded deeper in the case on the opposite side of the shaft. Dang.)

I wonder if the detent is installed correctly. Gotta pull the shaft to see.

Mrmerlin

I was going to suggest to inspect the locator ***** and springs for the shift shafts

Landseer

Thanks Stan, I think that's what needs to be done. Just edited my post with better info.

Might also be a distorted fork.