915 problem - no 1st, 5th, Reverse

[aldente295]

Yesterday I pulled away from a set of lights and at about 3000 rpm in 1st, the car jumped out of gear with a bit of a 'bang'. I pushed in the clutch, put it back in first, and... no first. Just revved. I threw it in second, and it engaged but was making a loud whining noise (similar to the noise you hear when you go in reverse).

I pulled over and had a quick look underneath; nothing obvious. I went through the gears and found the following:

1st: Nothing. Just revs
2nd: Engages, but with a loud whining noise esp. at low revs. Didn't feel 'right'.
3rd: seems to work normally
4th: seems to work normally
5th: Nothing. Just revs.
R: Nothing. Just revs.

I managed to get it home, and played around with the shifter adjustment, hoping that somehow it had just become misaligned or something.

I jacked up both rear wheels, put it in 2nd, and rotated the wheels. I could feel the diff engaged. Put it in 1st, nothing - free spinning.

I then drained the tranny fluid and opened the inspection cover. No metal chunks came out, the guide fork was in place and tight (drat) and the gearsets and dogs that I could see all looked perfect.

Then I put it back in 2nd, and spun a rear wheel while watching the gears inside the housing. No gears moved - it was just spinning the diff (which I believe is the correct behavior).

I then put it into 1st, spun a rear wheel - and the gears continued to spin as if it was in Neutral, even though I could see the gears appeared to be engaged. Put it back into neutral, and the gears continued to spin with the wheel.

So... tell me the bad news. What do we think happened?

I'll mention that this 915 box was purchased as a rebuild 2 years ago, when my original tranny died.

thanks guys - hopefully PP is back online again.


Al

[ivangene]

open your tunnel between the rear seats on the floor...move the shifter fore/aft while trying to keep the coupler from moving - how much "play" is there...might be those bushings under the shift tower (cup/ball)

if that is not worn too bad, try the same test but use move the shifter side to side and see how worn the coupler is....

maybe your bushings failed - simple to test

I get quite a few couplers that literally crumble into bits when the bushings are touched

[gregwils]

If it is the coupler bushings, count your blessings, the send Ed (ivangene) a PM to order his bushings. I had just replace my bushings 5,000 miles ago, but replaced them with Ed's because of all the positive feedback. Guess what, I have nothing but great things to say about the improvement in how my car shifts.

[DRACO A5OG]

OMG! this happened to me BUT worse, I hope it isn't in your case.

I dragged my car out of 2nd while on a freeway on ramp, pushed the clutch in to goto 3rd then I heard a loud Pop and she would not go into 3rd, whined then all gears lost. SNAP my main shaft at 2nd gear. All after a trans rebuild and wrench warned me about it.

+1 do as Ed suggested. +1 if itis a bushing or coupler, get his coupler you will not regret it.

[aldente295]

Thanks guys. Unfortunately the bushings are solid - replaced awhile back. I'm pessimistic of an easy fix because of what I saw when spinning the wheel in 2nd vs 1st. Very curious that I would lose three gears all at the same time. Can't be good.

[HawgRyder]

Perhaps the coupler to trans shaft is loose?
If the set screw gets loose...you will have too much side play resulting in not enough throw (left and right) in the trns shift shaft.
Also...it could be a little further into the trans...the shift fork set screws.
Bob

[aldente295]

Yeah I did check the coupler, and the screw was a bit loose. But tightening it didn't help. I actually removed the coupler altogether, and was able to manually select all 5+1 gears. Also, the fact that I could get 2nd told me that I was in the right plane for 1st, and being able to get 3rd and 4th told me that I wasn't out of adjustment top to bottom. So I 'should' have been able to get 1st.

Even peering through the inspection cover, I can see that 1st has been engaged - but no power is being transferred to the wheels.

What's the relationship between 1st, 5th and R? Could breaking something with 1st cause these other two gears to stop working?

[aldente295]

Rightio... on Sunday I dropped the motor. I'm still holding out a tiny bit of hope that the problem isn't 'terminal', but I had the day available to do the drop, so figured I'd better take it.

The transmission's now sitting on my workbench. Are there some tests that I can perform, to determine what problems exist? Imagine you were going to buy a transmission from someone - how would you determine if all of the gears were working etc?

Thing is, that the box was rebuilt only a short time ago, and it was working perfectly prior to the incident on Saturday. There's no evidence of metal shards or anything in there - I'm at a bit of a loss to understand what exactly happened.

Any ideas on tests I can try on the bench? Or should I be removing the nose cover?

[ivangene]

wow...I mean I have thought...Im hungry...I'll make a PB&J and just did it

but GEE, I have a few minutes I will pull my engine out and put the trans on the workbench

DUDE!!!

you rock!
I have my doubts this will be a problem for you for very long. I have no trans experience.....YET - best of luck finding something simple in there

[aldente295]

LOL thanks Ed. This was my second drop, so a lot faster this time.

....And I'm not convinced I needed to in the end. I pulled the nose cover off last night. Everything looks and behaves normally. I can't see any evidence of any damage.

And yet I still can't understand how the shifter could have gotten so far out of adjustment as to cause the issues I was experiencing. I can understand not having 5/R if you're not getting far enough to the right. But how do you also lose some front-rear adjustment in the left plane (no 1st, 2nd partially in) and yet the 3rd-4th plane is fine?? Baffling. I'm going to need to play with it some more.

[schumicat]

I wouldn't rule out the shifter itself if something wore out or broke internally. It is not hard to remove and you can check the shift rod and bushings at the same time if you haven't already.

Originally Posted by aldente295

LOL thanks Ed. This was my second drop, so a lot faster this time.

....And I'm not convinced I needed to in the end. I pulled the nose cover off last night. Everything looks and behaves normally. I can't see any evidence of any damage.

And yet I still can't understand how the shifter could have gotten so far out of adjustment as to cause the issues I was experiencing. I can understand not having 5/R if you're not getting far enough to the right. But how do you also lose some front-rear adjustment in the left plane (no 1st, 2nd partially in) and yet the 3rd-4th plane is fine?? Baffling. I'm going to need to play with it some more.

[aldente295]

That's exactly what I was thinking on my way to work this morning. I'll be pulling up the shift tower tomorrow.

[aldente295]

Results were inconclusive...

The cup under the shifter is intact and looks perfect. I replaced it a couple of years ago, so I would have been surprised if it wasn't in good condition.

The bushing that goes around the shift rod (the one in the bracket bolted to the bottom of the tower) is also intact. There is, admittedly, some slop there, but not a massive amount. How much is too much? Given the relative cost of replacing vs the pain of pulling the shift tower off (which I've already done anyway), I might as well replace it. But I'm not confident that this is the issue.

HOWEVER, if it's not that... I'm really at a loss. The only other thing I can think of is that somehow one of the shift guides has moved - ie the one on the 1st-2nd shaft. BUT with the nose cover removed, I'm able to put the inspection cover back on, and actually try shifting into all 6 gears while still being able to see what's going on. All gears appear to fully engage as I manually push, pull and turn the shift rod. The shift guides between 1/2 and 3/4 line up with the 5/R notch when I'm in Neutral. Everything continues to look completely... normal.

Another suggestion I've had is that perhaps the band on 1st has slipped out from under the dogteeth, preventing it from engaging first. Not sure how this would have affected engaging second, or 5/R... It's very hard to see 1st even with the inspection cover and nose cover off, I may see if I can pick up an inspection camera to have a peek right into the bowels of the thing.


As much as I'm hoping that there's nothing actually wrong, nothing would be more depressing than putting it all back together, putting the engine back in and having the same problem still there!

Anyway, I'll order the bushing and wait for the Swepco I ordered to turn up, and think about getting a wee camera. I'm away this weekend anyway, so won't have much of a chance to do much on it for the next week or so. I'll keep turning it over in my mind. Let me know if anyone has any other thoughts...

[aldente295]

Well, I rolled the dice and kinda lost.

Swapped out the shift bushing, checked and rechecked the operation of the gears and still couldn't see anything wrong. Decided to put it all back together and see if the problem magically went away... It did not. Started 'er up and had exactly the same symptoms - no 1st, 2nd noisy and no 5/R. Arrrrrrrrggh. One of the most depressing moments in recent memory.

Bit the bullet and drove it (gingerly) to my local mechanic. He's scratching his head as well, so it's clearly not something 'simple' that I've missed. So the sad truth is, I'm going to need to rip it all open again. Hence my other post asking if it's possible to just drop the tranny itself, to save the pain of having to repeat the entire engine drop exercise again. I think I know the answer, but I have to ask...

Once I get the transmission free, I'll be bundling it into a large bag and taking it to a pro for a deep dive diagnosis....

[aldente295]

Dropped the engine and trans again tonight. 2hrs 24mins! :-) Transmission's bundled up in a little sack, on its way to the shop tomorrow morning. So hopefully I'll have an answer to the puzzle this time tomorrow...

[aldente295]

...And I have the answer.

Input shaft has sheared :-(

My mechanic was swearing down the phone, because he's telling me that the shaft has clearly been WELDED to repair some sort of fault. I'm going to look at it tomorrow. He's never seen such a thing before, and is sure that's why it failed so soon (I bought it rebuilt less than 2 years ago). So I ain't so happy with the rebuilder I used right about now... Luckily everything else looks good inside, so hopefully it's just a matter of replacing 1st, then putting it all back together.

Unfortunately he's having some trouble locating a 1st/shaft assembly here in Sydney, so I'm sniffing around for one as well.

I remember hearing about an aftermarket 1st/input shaft that had a replaceable 1st gear. Has anyone used one of these before? Worth looking at? Or better just sticking with OEM?

Anyone have a 1st gear they feel like shipping over to Australia? :-)

[Joe Bob]

Dave at TRE has helped me in the past.....John Walker has a very good rep.....then there is Parts Heaven and dC automotive.......
915 stuff ain't cheap.....

[strikee]

Alan, there was a complete 915 transmission on ebay that just finished unsold for $1700 bucks. Its in QLD though. Just thought I would mention it.

Cheers
Ed.

Porsche gearbox - 915, in good condition. | eBay

[Fishcop]

Al, check the AU forum - I've responded and may be able to help you.