915 Stuck in Reverse

[cdadaa]

Looking at my rebuild photos, I don't see the switch pin. I don't think I put it in!! It didn't show up during the tear down either....hmmmm

Could this be the cause of the current situation?

[AMSRoadRunner]

I am about 75% certain that the shift rod thingy that actually moves the fork for Fifth and Reverse is not quite adjusted correctly and I will occasionally have problems getting into or like in your case, getting the trans to drop out of reverse.

To fix this (yes, the tire on the worn suspension bushings) I just run it between Fifth and Reverse a couple of times then from fifth carefully drop into neutral.

Hope that helps!

[Jon B]

Dan,

If you can shift into 3rd or 4th while stuck in reverse, and the transmission locks up, then your midcase interlock/detent plunger (#4 below) fell out of position. It's now sitting above the 3rd/4th shift rod. It's very likely that you pulled two shift rods foward, but only one back into neutral, leaving the trans stuck in reverse...

[john walker's workshop]

i'm assuming that this trans was never driven and you probably left it in reverse when the end cover was installed.

[cdadaa]

Is this roll pin you referred to (on the R-5 shaft)?

Yes, initially the car was driven about one block starting out in 3rd when I stopped to adjust the shifter.

[Jon B]

Originally Posted by cdadaa

On the initial test drive, it had 3rd 4th & R. After adjusting the shifter, it appeared that I got 1st, then I fiddled with the adjustment a little more and that's when everything stopped.

John,

That's often a possibility as well, but in this case he did test drive the car before it became stuck in reverse. There may be other issues involved as well. By the way, if you're stuck in reverse, the reverse light should be activated with ignition on. If so, the rollpin is in place, but has nothing to do with shifting.

[Jon B]

Yes, the rollpin is still on the 5th/Reverse shift rod in your photo, just ahead of the bronze fork. The rollpin only activates the reverse switch, it has no shift function, but allows you to drive the rod back into neutral.

[cdadaa]

Jon,

Do you suggest I disassemble the tranny and check the mid-case detent plunger? I remember working with the mid- case a couple of times during assembly due to the plunger slipping out. Could the plunger slipped out due the original mis-aligned shifter?

Thanks...Dan

[Jon B]

Dan,

If you can shift into 3rd or 4th while stuck in reverse, and the transmission locks up, then the plunger is absolutely out of position. It can only happen during assembly. In your photo above, the transmission is being assembled upside down, but it can occur anytime the midcase is handled. Yes, it's a good idea to correct the situation. The original poster to this thread just admitted he's still having issues. While the shift lever tower normally makes it difficult to engage two gears at once, it's a risk I wouldn't take myself. In the meantime, if you want to pop it back into neutral, follow the advice on page one, but realize it's a temporary fix.

[john walker's workshop]

when the trans is out of the car, remove the two tap-in plugs, one on top of the diff housing and one on top of the center housing and see if you can fish a detent out of the hole(s) with a pencil magnet. if so, you have a problem.

[cdadaa]

I will drop the engine and tranny this coming weekend and first check out whether I came access the plungers from the plug holes followed by disassembly. I'll keep you posted on what I find.

Thanks for your help and suggestions.

Dan

[cdadaa]

John, et al,

I pulled the engine and tranny today. I've got the nose cone off right now and I have no reverse switch pin! Not a clue what happened to it?? Does anyone have the specs' for this pin so I can fabricate one as I see they are NLA?

I pulled the plugs and fished out a plunger from the hole closest to the nose cone (front of car). Nothing from the other hole. I haven't removed the mid-case yet. Can I fix the plunger without disassembling the mid-case?

Thanks...Dan

[Jon B]

Dan,

This is exactly what I said had happened, the plunger fell out of position and was sitting above the 3rd/4th shift rod. No, it cannot be put back in place without pulling the midcase. This was probably Andrew's problem as well, it's a common reason why 915's find themselves "stuck in reverse".

[cdadaa]

Thanks,

I'll dig into the mid case tomorrow.

Regards,
Dan

[Jon B]

The reverse switch pin for a mag-cased 915 is part# 915.303.145.00. Are you sure it's NLA from Porsche? If so, someone probably has an extra they can spare- sorry, I don't.

[cdadaa]

I removed the mid case housing. As determined yesterday, short detent plunger is on the outer part of the shift rod.

Next step...place the short detent plunger on the inside of the 3/4 shift rod hole on the mid case housing and reassemble??

What configuration should the gears and shift rod be in for reassembly (i.e. neutral)?

BTW, the shift rod tightening bolts were never loosened, so I'm assuming that they don't need any additional adjustment.

Thanks...Dan

[john walker's workshop]

normally, you would slide a jig over the two roller bearings and shift rods and then eyeball the shift sleeves to be sure they are centered between their opposing gears. after the jig is on, slide on the 5th gear inner race and the big hub after that and snug the nut to pull everything toether. then adjust. so do your best with that. the notches in the two shift rods need to be on the same plane and have a small clearance between them.

[cdadaa]

Thanks John,

I do have the jig and will align as you suggest. I haven't removed the input or the pinion shafts today because I didn't find anything in the second plug hole yesterday, so I'm assuming that was okay.
I just replaced the other small detent plunger and it dropped nicely into the correct position INSIDE the case housing. During assembly last time I was working on the tranny upside down and it must have positioned itself on the outside.

Thanks...Dan

[Jon B]

Dan,

If you don't have the Porsche manuals, the top photo shows the adjustment between the 1st/2nd and 3rd/4th shift rods, roughly 2mm-3mm. As John says, make sure the forks center the sleeves between synchros. Shift one rod into gear, then make sure the other is locked out, so you'll know the rear plunger is in position. Put the rods in neutral when installing the midcase. Make sure the nuts holding the guide fork to the access plate, bottom photo, are secure.

[cdadaa]

Thanks All,

Got it all together and will re-install the engine and tranny this week. I'll let you know how it comes out. Thanks for the help!

I ended up fabricating a reverse switch pin from directions posted on this Pelican Parts forum.

This is an awesome forum!

Thanks again....Dan