915 Transmission Issue Query - was stuck in reverse
 

Hi,

I was hoping someone could assist me. I have looked through a number of on line sources.

I have a Carrera 3 MY77 and I was doing an oil change last weekend. Having changed the engine oil, and replaced the distributor, I put the car into reverse to back out of the garage. When I tried to put the car back into neutral the gear was still engaged. The position which felt more or less like neutral was still in reverse. It wouldn’t go into any other gear properly, and appeared to be like it was in two gears when it wasn’t in the neutral position. I checked the linkage and found one of the bushes on the coupling behind the seats was damaged. I temporarily fixed this but it wasn’t the issue. I changed the gear oil in case it would flush something out but no joy. I then checked online and found a reference to the reversing light pin which may be stuck out (pelican parts post). I pushed the pin back which sorted the problem. This was a relief.

My concern is that it may reoccur, at a time where the car isn’t over a pit. A post online had raised this before and suggested that play in the linkage can cause this issue. Has anyone here come across this issue before. I will be replacing the transmission linkage bushes and cup before I use it but it would be good not to be living in fear of putting the car in reverse.

Any thought would be appreciated. Someone told me that removing the pin would stop it reoccuring, however I would no longer have reversing/ backup lights.

Also, could someone let me know if 75W90 fully synthetic transmission oil appropriate for the 915 transmission? I hadn’t intended to change the oil so didn’t have any choice at the time.

Many thanks,

Ciaran

Hi Ciaran,

I entered "reverse detent" into the search engine then isolated the search to the 911 Tech forum.

http://forums.pelicanparts.com/porsche-911-technical-forum/583705-915-stuck-reverse.html

http://forums.pelicanparts.com/porsche-911-technical-forum/413466-915-stuck-reverse.html

http://forums.pelicanparts.com/porsche-911-technical-forum/202942-915-wont-go-into-reverse.html

Not sure if this will answer your problem but it gives you something to chew on.

Folk's use SWEPCO and Kendall pretty frequently here.

http://forums.pelicanparts.com/porsche-911-technical-forum/651996-i-have-915-lsd-transmission-fluid.html

http://forums.pelicanparts.com/porsche-911-technical-forum/630938-915-trans-fluid-question.html

Here is the search engine. You have to be logged on.

Pelican Parts Technical BBS - Search Forums

I had an issue where the pin at the head of the shifter shaft ripped out of the shaft. bushings were good but when shifting through gears the pin was sliding in and out of the hollow shaft and not moving it. Check the whole system from base of the stick to coupler, inspect the shaft for a crack or split.

Regards
Dave

Many thanks for the quick feedback. It is greatly appreciated. I have searched through the posts, and learned much about the way that the transmissions work. It seems that this detent issue is a pretty common issue however I’m still not sure of whether this detent issue is an original build issue or whether it can happen at a later stage. The transmission was rebuilt by a previous owner over 10 years ago and has covered approx. 10,000 miles since. This is the first time the problem occurred in my ownership (7 years). If something has moved out of its original place, could it be rattling around in the casing?
If it is the detent, can this be rectified with the transmission still in the car? If it is not a detent issue, would it be possible that the play in the linkage allowed excessive movement which was pushed back in place by the backup light pin?
Again, many thanks for your help.
By the way the previous owner created a fantastic website of the bodywork at 1977 Porsche 911 Carrera 3.0, Silver Coupe, restoration, bare metal repaint, engine rebuild, gearbox rebuild , for information.

I took some advice that I read in this forum after my 915 "stuck in two gears."

Never shift into or out of reverse unless you are DEAD stopped...foot on the brake stopped.

Have not had the problem since...should not have said that.

Remember that these cars were designed to have the engine and trans droped as one piece, quickly. Granted its not like tying your shoe but it is a relatively simple process when compared with many other cars. So in the worst case if you have to drop the trans and get it open its not a miserable job. But try and find the issue before doing any thing drastic like that.

If you have had the car for 7 years and put 10K on, you can use this as an excuse to drop the engine and do the valve guides etc. while you are in there this way the drop is not in vain if you dont find any thing in the trans.

Regards
Dave

Ciaran,

It was after I pulled and replaced my engine when my 915 was locked into two gears. I am sure that I backed my car into the garage and then probably banged the shift shaft when it was still in reverse when pulling or replacing the engine. A push on the reverse switch pin and problem solved, and.. knock on wood, has not repeated. Hopefully your issue is related to worn shifting components and once you tighten them up it will not happen again.

Wade

That's good advice Dave. I love doing my valve adjustment with the engine/tans out of the car. It inspires confidence and you get a chance to clean and detail everything before putting it back. I've made a custom jack that supports the engine and trans securely so I can do the job myself. All I do is get the car up on jack stand and rock it on the torsion bar ends to get the shift rod in and out of the tunnel. I've done it so often now I can get it out in about an hour and back in again and buttoned up in less than two.

Ciaran,

My 915 transmission shifts much better with non synthetic gear oil than with synthetic.

When I ran synthetic, my transmission hung up like you describe, since I switched to non-synthetic it hasn't. (knock on wood).

Shane

Thank you all for all the feedback. I'm very grateful.

I reinstalled the shift coupler last night, with new bushes, and replaced the nylon cup under the gearlever, and took the car for a drive. The gearbox felt similar to before but tighter as I'd have expected.

I was thinking about the various posts/ advice. I think that I'll adopt the following strategy. Change the oil to Swepco or Kendal type, and use the car for a while. I don't tend to use it too often anyway. I'll drop the engine when I source some heat exchangers and have a look in the gearbox while its out, and check and adjust the valves.

In the meantime I'll try to minimize the use of reverse gear.

Many thanks,

Ciaran

I would only add that you might leave the cover off to allow coupler access, and take time to fine-tune the coupler-to-rod adjustment over time as you drive the car. A little tweak can clear that stiff 3rd gear or allow the required play when in 5th.

Jdub, what do you mean with the required play when in 5th gear? I have a '86 Carrera and my 915 has now play in 5th what so ever. The shifter feels rock solid, all the other gears have some play when engaged. I only purchased it last month, so I'm a bit new to this.

915 Locked in reverse
 

I have gone over this and other forums recommendations on getting the 915 un-stuck. What I did not see was my symptoms.

Pulled into the drive in first gear, stopped, put into reverse to get aligned with going into the garage, then when going back to first the car did not move forward and bogged down. Put in reverse bogged down went nowhere, put it in neutral, it backed up reverse lights on.

If I pushed the clutch in it rolls both forward (into the garage, yay!) and back-wards with no problems.

I did do the shifter busing and coupler repairs and then adjusted per the book and from Pelican forum. It worked better, but third seemed to grind occasionally. No problems with reverse or 5th. More adjusting is needed this I can already tell.


So short story long.. the reverse switch and pin may work in this case? Maybe I'll try rocking the car first. was that for and aft or port to starboard rocking?

Some seem to have drained the tranny fluid others have not.

Thanks for your time.

CB.


Okay, an update. I have not done my fine tuning on the linkage yet, but here is what I wanted to post. I took a "is it plugged in" approach to my reverse
situation and I simply rocked the car from above the rear wheels to see if I could reinstate the pin or what ever caused my initial prob.

Well I am amazed to say that when I rocked the car from the passenger side I heard a slight "click" I rocked it a couple more times and another "click". Hopped in the car started it up put it reverse and WOW it went backwards!! Then the true test 1st gear.. it went forward!

I am thankful to the OP who mentioned shake the car!

August 23, 2014
Comments: I did the shift adjustment and replaced all the busing and installed a new coupler. Drove the car found all the gears, 3rd had a bit of a grind on occasion. Well took the car out for a spin last evening and when pulling into the garage, I went from 1st to Reverse at full stop backed up then when going back to first no movement. The engine bogged down as well with the clutch released.

With the help of my wife I was able to have her depress the clutch which freed reverse, and got the car into the garage.

I can go thru all the gear positions, but only in neutral will reverse work.

So is it wise to re adjust the linkage before going for the reverse pin under the reverse light switch?

I also read about rocking the car or running thru the gears hard could free the reverse in neutral prob.

Pointers, tips and solutions welcomed. I have only had the car for a few weeks...
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Comments:what I wanted to post. I took a "is it plugged in" approach to my reverse situation and I simply rocked the car from above the rear wheels to see if I could reinstate the pin or what ever caused my initial prob.

Well I am amazed to say that when I rocked the car from the passenger side I heard a slight "click" I rocked it a couple more times and another "click". Hopped in the car started it up put it reverse and WOW it went backwards!! Then the true test 1st gear.. it went forward!

I am thankful to the OP who mentioned shake the car!

What a life saver this thread is. Was adjusting my 915 today and got stuck in reverse \ ?gear....managed to engage reverse only and move car with clutch pedal down. I then tried to engage another gear (couldn't get neutral) ....removed the reversing switch and push the pin fully home. Changed gear oil at the same time. Works fine now.

I never knew 2 gears could be engaged at the same time, assumed my gearbox was shot.

Thanks !!