Trans Rebuild: What is this part?

[SpeedracerIndy]

In the middle of rebuilding my 915 and trying to figure what this part is, and if it is supposed to look like this. It is the fork attached to the access pannel. Item #6 in the image. I am wondering if it is supposed to be worn like it is in the pictures (arrow). Also, when I took the transmission apart, the fork was loose, and wondering if that could have caused my grinding while the car was in 2nd gear. Trans would grind really bad if I pulled down on the shift lever while driving in 2nd gear.

[rcecale]

CD, don't recall seeing that notch in mine when I had it off, however, in this pic it doesn't look like it was there.


Also, early on in my thread, John Walker made reference to that fork being loose and told me to check it to be sure it was firmly attached. Mine was.

It acts as a pivot point for the shift linkage, so if it was loose, I would think it could/would cause shifting problems such as not shifting all the way into gear.

Randy

[john_colasante]

My feeling is that notch will not make any difference in shifting because the shift actuator contact point is between the forks. That notch may be for clearancing of the shift fork.

[Jadams1]

Mine did not have the wear marks either.

[konish]

CD,
Static shift fork is the item depicted as #6. Can't help you with the wear marks, however if they don't typically have them I think we can all assume that something isn't quite right(?)

R/
Dustin

[SpeedracerIndy]

Thanks! That's pretty much what I expected. If you look at mine, you can also see that it looks like it has been excessively hot by looking below the wear marks I pointed out. I have inspected every part of the gears and syncros and could not find where the fork was rubbing. Since it's brass though, I wouldn't expect it to harm the gears. I am certain that it is the cause of some of my shifting problems. It was pretty loose. I could move it about 1/4 cm in each direction.

As I look at my pics, I can see how the fork is supposed to guide the shift lever. Here is a pic of the access panel before I took everything apart:


From that pic, I can't see what the fork could have been hitting though.

Here is a pic of my syncro and dog teeth from first gear. Good pic showing how a syncro and dog teeth are NOT supposed to look. The syncro is upside down though since I had it apart and set it down the wrong way. Second gear was much worse than this if you can believe it. Sorry for the poor quality pics, I am just figuring out how to take close ups with my digicam.


Just for an excuse to post a pic, here's 3rd and 4th syncros, the way they are supposed to look:


Any of the experts know what the fork was rubbing against to cause this? And, is this something that should be replaced, or will it work ok the way it is?

[rcecale]

Originally posted by CDiercks
I have inspected every part of the gears and syncros and could not find where the fork was rubbing.

Looking at the notches in your fork and while I am far from being an expert, I would guess that there isn't a rubbing problem. The notches just seem too squared to the fork itself to be there other than intentionally. Why? I have no idea, but they just seem too uniform to be an "accidental wear" thing.

If the gears themselves were rubbing against the fork, you would have noticed that. Also, they would be rounded, not squared off and flat, like they are. The heat marks could be from when the notches were milled into the forks. They could also be from some sort of heat treatment as well. For what it's worth, I wouldn't worry about them...but again, I'm no expert.

Originally posted by CDiercks
Sorry for the poor quality pics, I am just figuring out how to take close ups with my digicam.

If you have a zoom lense on your cam, try standing back a ways...18 to 24 inches, if possible and use the zoom feature to get closer. It soothes a lot of the glare when you use the flash.

Also, a little side-lighting, from a flashlight or shop-light, helps.

Randy

[wevoid]

CD,

The wear marks on your pivot fork are the result of contact with the adjacent gears from one or a combination of the following;

The fork being loose

The gear stack moving as a result of the pinion bearing rataining plate being loose

The pinion thrust bearing being excessively worn

By the looks of the one M6 stud that is showing excess thread above the nut, that one might have either pulled, or been replaced with a longer stud after the initial stud was lost / removed.

The grinding noise can come from this fault - light pressure on the gear lever, can rock the now mobile pivot fork, or gear stack until it touches the 3rd or 4th gear on the pinion shaft, hence the wear and the noise. Extra force on the lever would have either selected neutral, or weighed heavy on the pivot fork and made the noise even worse.

The part is heat treated, induction hardened, that leaves a peculiar heat witness pattern on the fork, yours seems to have added color from the heat asssociated with the friction of rubbing on the edge of the gears.

The part is still fine to use. Make sure the 3 off M6 studs are tight in the bottom cover and new nuts / washers are used to fasten it. Do not use nyloc nuts, the heat is sufficient to render the nyloc ineffective.

If I work on this install, I use all steel lock nuts, after I have glued the studs into ther cover with red loctite.

Regards

Hayden

[SpeedracerIndy]

Thanks for that detailed explanation!!! That makes perfect sence. I also wondered about that long stud. I will take it apart to make sure it isn't pulled. What about using locktite to keep the fasteners from comming loose again, is that advisable?

[wevoid]

CD,

Sure, Loctite is good insurance, beware that at the oil temps in the transmission, some of the Loctite products have significantly redced performance. It's a good extra layer of insurance over new hardware.

I like the all steel locknuts, due to the fact that if the stud yields in the aluminum cover, then the nut will not spin off, as a std. nut and split washer might permit....

On our GateShift kit, we use through bolts (for assembly reasons) that are sealed with o-rings, then lock wired on the outside. It is also possible to modify the O.E. bottom cover to use through bolts, it's a good way to salvage the bottom cover if you have lost your confidence in the M6 threads tapped into the cover.

Regards

Hayden

[oneblueyedog]

Funny thing when I resealed my transmission during rebuild, the fork on that plate was loose as can be. The lock washers had broken underneath the nuts. The studs in the plate were boogerd up from the shifter fork wobbling around. I repaired the damage and peened the nuts after torquing them down.

It shifts great now!

Lee
78 SC