915 5th / Reverse problem

ja911sc · 11-04-2003, 10:01 PM

I'm having a shifting problem with my 78 911sc. The problem started after my wife drove the car last week. She had no problems while driving. Anyway, I went to move the car and could not get the shifter into reverse. No grinding, but no gear either. The first thought I had was a shifter problem. I moved the car into the garage and pulled the shifter out. The previous owner installed a factory short shift kit, so I wanted to make sure there were no issues with it. It passed visual inspection - no loose parts. I moved on to the coupler. The coupler has a little play in it - less than .125" forward / backward. I used the Pelican directions for adjusting the shift linkage with no luck. I tried to manually "pull" the transmission into reverse by rotating the coupler counter clockwise (facing front)to the stop and "feeling" for 5th/reverse. Pulling the coupler / shift rod towards the front of the car all I can get is 4th gear. Has anyone else had this problem before? Before I took everything apart - there was resistance in the fifth & reverse positions that would not allow the shift lever to push into the gates.

Eugene at Pelican Parts · 11-04-2003, 11:54 PM

Just to clarify, do you mean
A: when shifting into 5 or R, there is absolutely no resistance, and the gears do not engage?
or
B: the shifter won't move all the way to the right into the 5-R plane at all?

Either way, if you have already confidently eliminated the shifter and coupler mechanisms, you'll have to open up the end cover of transmission to investigate further. If it is situation A, it's likely that the 5-R shift fork pinch bolt has loosened up, allowing slop in the operation of the slider. However, if it's B, then perhaps the 'finger' on your shift rod is not lining up and slotting into the 5-R selector shaft correctly. Here's a poor angle of what you'll be looking at.

Did it shift well through all the gears before? Although it's not difficult to examine beneath the end cover of the transmission, you should consider a full rebuild if the other gears are giving you any trouble. Better to do it all at once, as many of us often say to ourselves.

khyden · 11-05-2003, 12:53 AM

Hello,

one small question regarding shifting with the 915 gearbox. Is there any users of the product made by seinesystems (www.seinesystems.com) "Spring-loaded mechanism for your shift housing. For your 915 or 901 transaxle! Spring-loaded feedback prevents expensive engine damage."?

Kris

ubiquity0 · 11-05-2003, 06:55 AM

Kris- do a search . There have been a few threads on this & I think the guy that makes it posts here.

1fastredsc · 11-05-2003, 07:10 AM

I wish i had had that picture 6 months ago. I just finished rebulding my 915 about 2 months ago (it would have been quicker but i'm doing the motor as well). Not to scare you but i did the complete rebuild for other issues besides my reverse problem. And the reverse problem i had was similar to what you describe except that i was stuck in reverse. After opening the trans, it turned out that gear selecting fork got loose and stayed in reverse while the selecting shaft slid freely through it. All the other gears worked just fine except that reverse was permenantly engaged. You'll have to drop the engine/trans, open the rear most access to the trans to reveal 5th and reverse, and you'll find out almost immediately what's up.

Early_S_Man · 11-05-2003, 08:20 AM

Another possibility is that the guide fork #6 has come loose from the cover plate #5 in the diagram below. Drain the oil and remove the plate to check for the three M6 nuts -- #8 that may have come loose. Fairly common occurrence that needs to be addressed with Blue Loctite!

ja911sc · 11-05-2003, 08:30 AM

It doesn't appear that the shifter will move into the 5th/reverse plane. The lever will go to the right with the normal resistance from the shifter. However, if I try to push the lever "up" into 5th or "down" into reverse there is a lot of resistance (I haven't tried to force it in either gear for fear of damage).

ja911sc · 11-05-2003, 08:36 AM

Alwayswong:

It was shifting fine prior to this problem. It also appears the problem is limted to 5th/reverse as I can shift in and out of the other gears easily with no grinding.

1fastredsc · 11-05-2003, 08:42 AM

Yup, with the exception of being stuck in reverse your problem sounds identical to my car's. Take the back cover off and inspect.

ja911sc · 11-05-2003, 09:00 AM

I guess I'll be pulling it out this weekend. Thanks to all for the responses. I'll keep checking the post for any other suggestions & update when I get my hands dirty.

Eugene at Pelican Parts · 11-05-2003, 09:20 AM

I'll second that. Once that cover is off, make sure you replace the paper gasket, the shift rod seal, and the O-ring atop the shaft that the reverse gear is on. Other seals that do not require further disassembly are the axle seals, the mainshaft seal, guide tube o-ring, and shift plate gasket.

Try not to drive the vehicle or at least don't fuss around with the shifter too much since it's likely you can get stuck into gear. Also, with the shift fork loose, it's possible the slider could nick reverse at any time. Anyway, just be careful and good luck.

power · 04:38 PM

I'm with Warren on this one. A long time ago when I first purchased my 911 T (it has a later 915 Transmission, I think around same year as yours) I had a similar problem to yours. The problem was fixed by taking off the guide fork cover plate and monkeying with the guide fork. I can't remember the exact details, although I rememeber you can see a whole lot through the open cover and it becomes a lot easier to diagnose without having to remove engine/transmission. I think the dongle (number 2 in Warrens diagram) had been forced outside of the fork somehow (probably due to heavy handed shifting at that time) and I re-aligned it sealed it up and has been fine ever since. Of course I had expert guidance from the board members.....I think JW actually told me to look there.