Need help on a recent 915 rebuild as its a disaster

[Trackrash]

Originally Posted by Steve@Rennsport

Did the shop use a lot of Rausch & Spiegel parts????

If so, precisely which ones??

Exactly my thoughts. Some of the aftermarket dog teeth are not in spec.

Also I did not read when you have trouble getting into 1st. If when moving you are trying to downshift into first? Or while the car is sitting still?

[ReconTrojan]

This is all so great thank you.

I have forwarded ALL of your comments. As far as when I am shifting into first, only at a complete stop. The only gears that are accessible consistently are 2-3-5. Reverse today taking it back in took 5 minutes and I thought I would pull the shift knob out trying to find it. When I parked the car they moved it before giving me a ride home- they suffered the exact same problem. No one is disputing this is mechanically not correct

I made the choice today and they agreed to remove the gate shifter, check everything again with it removed and go step by step. The mechanic has 30 years of 915 experience so Im not sure what else can be said. He has worked on my 951 & Spyder and zero issues. When I met him he was rebuilding the transmission of a 959 so competence isn't the issue I think as someone mentioned is an accumulation of lots of things that had has arriving here. The tear down starts Monday morning and I have been assured no other project will bump it till completed.

Thank you all.

[Bob Kontak]

Originally Posted by cmcfaul

as 1st gear synchros are designed to only engage when the car is stopped.

I will say that after my rebuild in 09 I could slide into first when going pretty slow - under 10mph I felt like I was cheating the devil.

Did it maybe twice then never again for obvious reasons.

This was after 20 years of driving the car without a hint of first gear engaging in motion.

[uwanna]

Originally Posted by Bob Kontak

I will say that after my rebuild in 09 I could slide into first when going pretty slow - under 10mph I felt like I was cheating the devil.

Did it maybe twice then never again for obvious reasons.

This was after 20 years of driving the car without a hint of first gear engaging in motion.

I have a 915/70 LSD trans that I bought brand new in the factory crate years ago ($1500 back then, imagine that!) when I put a 3.6 into my '80SC. I have been shifting into first while moving ever since I installed it 24yrs ago with nary a problem. Usually don't downshift to first above 10-15mph or so because I don't find it necessary, but don't see why it wouldn't work. After all, why have a first gear syncro if you're not supposed downshift to it! Could use a non syncro like reverse gear if you're only meant to shift to first when at a dead stop!

[john walker's workshop]

Exactly! They were designed to use 1st while moving slowly. You don't just jamb it in. You move the shifter toward 1st firmly, and wait a split second until the shift is accepted by the syncro mechanism. If it grinds, it's worn.

[Duc Hunter]

My 915 in my project car was rebuilt my RSWerks in Atlanta for a PO. IT is VERY hard to get into first and second gear and had Swepco in it. I threw in my favorite synthetic tranny oil to see if it would help, and also because I had no idea how long the Swepco had been in the car sitting (car was not running for years). When I swapped it out to plain old Dano gear oil to break it in. It is getting better and better. On mine it is almost like teh gates are closed..it just won't go into gear (1 & 2). As I work it now though it is getting better and better. I have a Rennshift and woudl not change it out for anything. My mechanic thinks they put in stiffer bushing springs (think that is what he said) which may make it shift stiff for a while.

[ischmitz]

Let me make a couple of points as I went to almost exactly what you did. I had to replace my input shaft to the later version and upgraded 3rd/4th slider/operating sleeve as well to make it a stronger box. I flipped the 1st and 2nd gear synchros (almost zero wear since last swap) and got a new 3rd/4th synchro bands. So more or less a complete rebuilt just like you. In the process I decided to treat myself to the Wevo internal gate shift kit and the Wevo shifter with the PSJ coupler.

I talked to a lot of people about whether the Wevo gate shift kit is a sensible upgrade. To my surprise I got mostly negative comments along what John Walker stated.

- "will make it shift like an old Ferrari with the gate pattern machined into the shifter cover"
- "you will need to develop new muscle memory to find gears"
- "shifting will be very positive and notchy"
- "will take away from the 'charm' of a 915"
- "adjustment of the shifter coupler will be extremely difficult to get perfect"
- "waste of money"

And the list goes on and on, you get the drift. I also talked to Hayden about that and he was very open about there maybe being a small change. But he assured me the gate shift has been installed many times and almost everyone liked it.

Well, despite all the negative comments I went ahead anyway and got the kit and we installed everything. Honestly I was a little nervous. I put the new shifter and shift coupler in and adjusted the coupler without even reading any instructions. Logic tells you transmission into 3rd gear, lever roughly where it needs to be fore-aft (guided by the springs into 3rd/4th plane) and then tighten everything. With that I took it for a test drive.

WOW, let me be clear. It shifted just perfect. Not a single of these comments came true. And believe me I was looking for any noticeable issue or strangeness when shifting. When shifting into first gear I made two observations:

1. When I move the lever all the way left and then forward it goes in much easier. This is likely the internal gate shift doing its job. When I do the soppy diagonal move it takes a little more force to get it into gear.

2. When trying to put it into first after having been on the clutch for more than 30 seconds it get harder to do this. This is because the input shaft is spinning down to a stand-still. Now the dog teeth need to move the shaft to engage. In this case rather than forcing it I quickly release the clutch a bit, step back on and then put it into first. BTW, staying on the clutch wears out the TO bearing and is bad driving.This behavior has been the case before with my 915 and is perfectly normal and expected for a 915. All in all I couldn't be happier with the Wevo stuff installed. I can't say if having or not having the gate shift kit makes a big difference. In any case I really like the way it shifts now. I would always do it again.

Generally, if you have a hard time getting into first it's either because the input shaft never spins down fully (clutch is not fully disengaging or pilot bearing is grabby) or because it came to a standstill. Should be easy to find out which one it is.

Further I believe you do want to give it some miles/shifts after everything is brand-new before you render a final judgement. The new synchro band surfaces might still settle in a bit. But in the end it should be pure bliss.

Ingo

[KTL]

The strike against the R&S synchro teeth is that they refuse to back-cut the teeth to allow the synchro band to sit inside the teeth as designed. It's supposed to be a 9 degree back-cut. So, technically speaking, their design immediately alters the fitment of the synchro band and it may not measure up to the typical new installation diameter. I think this is laughable since the factory manual makes a point of saying this installed dimension should be checked in order to determine the wear condition of the synchro teeth!

Definitely take a look at the release fork. These transmissions are not getting any younger, obviously, and the forks are starting to crack more frequently. Going forward, I think folks with original forks should make a point of replacing them as a matter of course, just like we typically replace the T/O release bearing.

Here's some pics in this thread showing the cracked fork condition. Clutch/Flywheel Analysis

Agreed 1st gear is not one that is willing to accept a downshift while moving at a considerable speed. 1st gear is such a high ratio that the synchro needs to do a lot of work to match engine rpm & trans input shaft speeds. So to do yourself and your trans a favor, you should double-clutch it to match speeds. I do this all the time in my racecar coming off the track into the pits.

-Push in clutch and select neutral
-Release clutch and bring up rpms to where you think they need to be for 1st gear
-Push in clutch and select 1st
-Release clutch while still keeping rpms where they need to be.

The above is tough to do for people who blip or stab the throttle to match rpms when downshifting. Double-clutching is easier when you're someone who's the type that presses & holds the throttle during your rev-matching/heel-toe technique.

[Elombard]

Interesting Kevin, I never thought about holding the throttle, I am a "stabber". Have to play around with that. Very interesting.

[ReconTrojan]

Thanks for these additional comments. They will add greatly not only to my plight but future ones as they come across this thread.

I had asked months ago when I got the 911 what was the 915 like when new to those that remember. To a person they all said it was just fine/great. Had I to do it all over again I probably would have held out for a G50 but this 911 was perfect for me. I had no problem spending the money I did to make it great. While the gearbox issue was annoying it was only first gear and I lived with it for a couple of months until I decided to make right.

I liked the WEVO shifter, researched the best I could on the internal gate shifter ( not that much information out there but nearly all of it positive)

It's been stated that every Porsche has a story of its own and when I was told that first gear was being a problem I was beside myself after a rebuild. But obviously after driving it and 2nd gear and reverse also problematic everyone involved agreed it was some sort of mechanical error.

I made the choice to remove the WEVO for many reasons but the foremost to eliminate a variable from OEM. We used the best parts on the rebuild as I had researched that and spoke to the best shops. I'm confident its not parts or fluids. Something in the process was not done right or over-looked.

As I type this the gearbox is out and WEVO removed and everything being checked again. I won't take the car back on a simple checklist, every time I look for 1-2-3-4-5-R it works and no noises that were not present before this started. Very simple, everyone is on the same page.

I hope to get it back by Thursday.

As an aside, I had the car for one day and installed the Porsche Classic Nav system....I love it from the 20 minutes I played with it.

Again, many, many thanks for all the contributions. There are not only knowledgable people on here but generous. Thank you.

[ReconTrojan]

*Update*

So the shop has the car. On a hunch they removed the WEVO short shifter and installed a factory shifter from a 911 SC and was told it shifted " fantastic in all gears"

So....

A factory shifter with a WEVO internal gate shifter, shifted well. But a WEVO shifter with said gate shifter sucks.

I told them to remove the gate shifter, restore to stock and leave the WEVO short shifter.

I bought that from them as well. I also told them to call WEVO for a heart to heart and see what the issue here is. My view from 1000 yards and dirty lenses is the gate shifter has to go regardless and I will remove anything not OEM and go from there.

Thoughts?

[ischmitz]

My thoughts: Re-read my post, it works perfectly fine when done correctly. I know because I drive it with both and have no issues. I'm using sport mounts at the transmission and the PSJ coupler. Either your shop isn't adjusting the coupler correctly or the forks in the 915 are not adjusted properly or expectations are off.

[ReconTrojan]

Originally Posted by ischmitz

My thoughts: Re-read my post, it works perfectly fine when done correctly. I know because I drive it with both and have no issues. I'm using sport mounts at the transmission and the PSJ coupler. Either your shop isn't adjusting the coupler correctly or the forks in the 915 are not adjusted properly or expectations are off.

I can only speak to my expectations. Being able to shift into 1st, 2nd and reverse I think are not outrageous. The shops first response upon receipt of the car was how did I possibly drive it in that condition.

[ischmitz]

Originally Posted by ReconTrojan

I can only speak to my expectations. Being able to shift into 1st, 2nd and reverse I think are not outrageous. The shops first response upon receipt of the car was how did I possibly drive it in that condition.

That last part is an interesting statement from the shop. I assume a shop that rebuilds and installs a 915 takes the car out for a test drive before turning it over to the customer. This begs the question if something deteriorated (shift coupler clamp nut loose) or whether the car left the shop in that condition?

I only threw the expectation statement out there because a 915 will never feel like a modern 5-speed or 6-speed gearbox. And maybe you need to have driven a couple of 915 until you get a feel for the spectrum of what a good-shifting and a bad-shifting 915 feels like. You see both extremes out there. Some have a terribly-shifting 915 and non-existing bushings and motor away gritting their teeth thinking it is perfectly normal for a 915. Others have a great-shifting 915 and think it's borderline unacceptable.

That out of the way there really aren't that many variables where things can go wrong. Let's assume the shop didn't make any grave mistakes when putting the stacks back together (order of washers etc.). That leave very little that could have gone wrong. I believe you can put the first-gear brake band assembly in backwards but that's about it. Then the adjustment of the internal forks on the shift shafts need to be spot-on. Ask them if and how this was checked and adjusted.

After that it's coming down to the external shift coupler adjustment. There are two variables: Fore-aft and rotation. Is it possible the clamp wasn't tight enough and this is why it's gotten so bad?

Keep us posted and good luck. I really hope you get this sorted out
Ingo

[ReconTrojan]

Originally Posted by ischmitz

That last part is an interesting statement from the shop. I assume a shop that rebuilds and installs a 915 takes the car out for a test drive before turning it over to the customer. This begs the question if something deteriorated (shift coupler clamp nut loose) or whether the car left the shop in that condition?

I only threw the expectation statement out there because a 915 will never feel like a modern 5-speed or 6-speed gearbox. And maybe you need to have driven a couple of 915 until you get a feel for the spectrum of what a good-shifting and a bad-shifting 915 feels like. You see both extremes out there. Some have a terribly-shifting 915 and non-existing bushings and motor away gritting their teeth thinking it is perfectly normal for a 915. Others have a great-shifting 915 and think it's borderline unacceptable.

That out of the way there really aren't that many variables where things can go wrong. Let's assume the shop didn't make any grave mistakes when putting the stacks back together (order of washers etc.). That leave very little that could have gone wrong. I believe you can put the first-gear brake band assembly in backwards but that's about it. Then the adjustment of the internal forks on the shift shafts need to be spot-on. Ask them if and how this was checked and adjusted.

After that it's coming down to the external shift coupler adjustment. There are two variables: Fore-aft and rotation. Is it possible the clamp wasn't tight enough and this is why it's gotten so bad?

Keep us posted and good luck. I really hope you get this sorted out
Ingo

Ah let me eliminate that confusion. My local shop uses someone we both know that opened his own small 915 repair shop in Pasadena. So they dropped it and reinstalled it. After the reinstall by my local shop is when I drove it first. they had driven albeit briefly and noticed the shifting issues but I needed to get this Porsche Classic installed before my 30 day window ( if there were any issues) so I took the car plus I wanted to check it out myself.

The car was flat bedded to Pasadena and the rest is covered by my other posts.

Both parties are not worried about the extra work needed but just want me happy. We are all fluxed at the recent developments and nothing makes sense but I totally agree with you and have made it clear that there is something wrong and since both parties have had their hands in the car off and on for 5 months on various things I wanted done for over 20k I'm obviously not in the mood for anything less.

Before I took the car in I had pretty much understood the 915. I could get in 1st gear some of time naturally and if I revved the engine most of the time. I was just growing weary of taking off in 2nd gear. The evidence showed first gear damage and the slider 2/3 and I replaced everything. So this isn't or shouldn't be rocket science.

[Matt Monson]

Originally Posted by KTL

The strike against the R&S synchro teeth is that they refuse to back-cut the teeth to allow the synchro band to sit inside the teeth as designed. It's supposed to be a 9 degree back-cut. So, technically speaking, their design immediately alters the fitment of the synchro band and it may not measure up to the typical new installation diameter. I think this is laughable since the factory manual makes a point of saying this installed dimension should be checked in order to determine the wear condition of the synchro teeth!
.

While it appears that the root problem on this car is likely something else I want to address this specific comment. Last week I was taking a gear order from Jerry Woods and we were talking about this issue. According to him R&S have been listening and for at least the most recent production run (which I have no idea when units came to market) they have been doing the backcut. Jerry used to modify all teeth, whether they were own or R&S. He says this is no longer required on the R&S teeth. I would still always measure the loaded dimension with synchro in place but it appears that these parts can now be trusted.

[Reddy Kilowatt]

There is nothing inherent to the 915 that makes 1st gear unusable (obviously). It's a perfectly good gearbox. You just need yours fixed correctly (obviously).

[KTL]

Good point by Matt, and he would know more about that than most. But the fact that those were out there for so long would probably rear it's head for some time to come? Those dog teeth don't fly off the shelf all that fast. Or is the flip side of that, the dog teeth are something usually ordered on an as-needed basis and therefore the older non-back-cut teeth would disappear from the market rather quickly? I honestly don't know.

[Matt Monson]

Originally Posted by KTL

Good point by Matt, and he would know more about that than most. But the fact that those were out there for so long would probably rear it's head for some time to come? Those dog teeth don't fly off the shelf all that fast. Or is the flip side of that, the dog teeth are something usually ordered on an as-needed basis and therefore the older non-back-cut teeth would disappear from the market rather quickly? I honestly don't know.

I think for most shops, and especially DIYers, it is an as needed item. I never kept more than a few of them on the shelf when I was doing rebuilds. I could always get them in less than 24 hours from the standard wholesale houses when I have a build to do. I know that SSF only has the fixed ones, and I suspect that Pelican would be the same way for anyone here looking to rebuild their own box. Some of the old ones will be in circulation for a while, which is part of why I suggest always measuring the loaded stack, and that is something you might want to do before you press the teeth onto the gear.

BTW, when I wrote "new" above it was supposed to be "oem". Stupid auto-correct.

[ReconTrojan]

Thanks guys. All of this information is being forwarded. At the very least this thread will serve as an excellent source of knowledge for those in the future. I hope to post the culprit and cure in the very near future.