915 Transmission Questions

Randy803 · 03-24-2003, 04:27 AM

My 911 was shifting great in all gears except that you could not downshift into first without coming to a complete stop or it would grind. I continued to drive the car as this wasn’t that big of a problem to overcome and I knew it was just the snycro. All of the sudden the car refuses to stay in first and pops out when I start off and third gear refuses to stay in gear now???

My question is -- Could the First gear problem be affecting third gear somehow? I had no third gear issues until first gear bit the dust. I have parked the car until I have a chance to pull the tranny but I am curious as to what I may find inside.

Also, anyone have a perfect condition 1980+ aluminum 915 trans they want to swap even for a 2.7 motor complete and running? Would save me some time..............

JackT · 03-24-2003, 04:32 AM

Have you tried adjusting the shift coupler? It may be that the coupler is not allowing the transmission to go all the way into the top of the shifter gears.

Randy803 · 03-24-2003, 04:36 AM

No I hadnt thought of that, I just asummed since it was working fine and then started the pop out thing in first it was time for a rebuild. From what I have read on the forums that seems to be the standard deal for first, it grinds and then pops out as it gets worse. I will try this tonight and see what happens, Thanks.

JackT · 03-24-2003, 05:03 AM

Randy, I am in Columbia. If you need any help adjusting the coupler, let me know.

john walker's workshop · 11:00 AM

DANGER! (maybe). the little teeth that hold in the syncro, brake band and stop dogs may have broken off. you will most likely find them in the drainplug magnet. the problem is, that all those pieces (syncros, band, dogs), can go thru the gears like a washing machine wringer and do way more damage than you have now. never drive one with this problem until it's been investigated further. it may be the coupler, but be sure.

Randy803 · 03-24-2003, 07:54 AM

John,
Are you saying this IS what has happened to my tranny or might be what happened? I trust your knowledge 100% so on your word I will yank her and start rebuilding. Should I attempt the adjustment or go straight to rebuilding it? Thanks guys!

N11Porsche · N11Porsche's Garage

John Walker is spot on, as usual. 5 years ago, shortly after I purchased my 911SC, those very symptons started happening in my transmission. I kept driving the p-car and made adjustments to the coupler. Problem didn't get better and didn't seem to be getting worse. Then on a drive, far.....far from home, the car would'nt go into any gear or shift. Finally got it into 4th gear and was able to limp home. Drained the transmission and all sorts of gear and syncro parts came out in the oil

$$$ later the transmission was completely rebuild, gears, sycros, bearings, etc. I pulled the Weltmeister short shift and went with the factory short shift as per my mechanic. He said the Weltmeister does have a shorter throw, but because of the leverage created, it puts more stress on the transmission when you shift. Good enough for me. 5 years later the transmission still shifts smooth as butter, both upshifting and downshifting. When I see guys post about the 915 and how it's "normal" to not be able to throw fast shifts either up or down, all I know is mine can be speed shifted either way with no problems. Take John's advice and don't drive it until you have it sorted out. Start with the coupler.......good luck.

john walker's workshop · 03-24-2003, 08:27 AM

just be sure it IS the coupler, or bushings before driving it any more. if nothing looks out of wack, drain the gear oil and check the manget for teeth. little teeth, about 1/8".

Randy803 · 03-24-2003, 08:37 AM

Hey John, I have a 1976 Magnisium 915 sitting on the floor in my shop could I just swap it with the 1980 aluminum if need be? Will it all bolt up? Worst case I would have my car on the road while I muttle my way through rebuilding my tranny.

Gunter · Gunter's Garage

To my knowledge, the '76 has the same 8/31 Ring & Pinion ratio and the only difference is the 2nd gear ratio. I don't know if the '76 has the helper "C" spring.

john walker's workshop · 03-24-2003, 10:35 AM

the 76 will go right in. it has the helper spring, and the axle flanges relate to the CVs. being that both 1st and 3rd have the same problem, you might get lucky and find it's a front bushing or rear coupler bushing problem.

Randy803 · 03-24-2003, 10:41 AM

One can only hope and pray! When I get home tonight I am going to see if the issue can be adjusted out. Thanks to everyone for the helpfull information!

Randy Webb · 03-24-2003, 01:45 PM

When you drain the tranny, put in Swepco 201 - it helps quite a bit. Then start checking the shift coupling (and adjust or rebuild), and the shifter. BUT, the abrupt and very large change makes it sound like you have a spendy problem. The magnetic drain plug and filtering of the fluid may tell you. But do the other stuff 1st -- it's cheap and needs to be done every decade or so anyway. In the worst case, you will have a fine shifting car after doing all the above and fixing the tranny. In the best case, you will have a fine shifting car.

widebody911 · widebody911's Garage

BTDT - your trans is broken. Period. It's fixable, but the more you try to drive it, the more expen$ive it will be.

Gunter · Gunter's Garage

Widebody Thom: Could it be that the 915 doesn't take the output from a 3.6 Liter engine? I mean, they gave a G-50 to a 3.2, so............?
BTW, your mailbox is full

Randy803 · 03-25-2003, 04:10 AM

Ok my trans is toast! I pulled the drain plug and just like you all said lots of little teeth and metal on it. I called Motor Meister and they are sending a truck to pick it up Monday morning to rebuild it. I decided that I didnt have the time or the courage to rebuild it myself. Once again thanks for all the help and advise on this issue.

ChrisBennet · ChrisBennet's Garage

Quote:

Originally posted by Randy803
Ok my trans is toast! I pulled the drain plug and just like you all said lots of little teeth and metal on it. I called Motor Meister and they are sending a truck to pick it up Monday morning to rebuild it. I decided that I didnt have the time or the courage to rebuild it myself. Once again thanks for all the help and advise on this issue.

OMG NO! Call them back. Don't send it to MM!
Do search on this list for Motor Meister!
-Chris

Tim Walsh · Tim Walsh's Garage

DO a search MM does not have a good reputation for rebuilds at all. There are several other places that will do a good job and even do a tranny swap to get you up on the road right away.

DON"T GO WITH MM!!

jet528e · 03-25-2003, 06:44 AM

Agree - have heard only negative about MM - First see if Johnny Walker's Work Shop will take it via UPS. If not, Gary Fairbanks in Norwalk, CT, 203-866-2466, has an excellent reputation and specialized only in Porsche Transmissions (901 & 915). He has a two day turnaround and ships and receives via UPS. Another that I've heard good things about is Lone Hill Engineering 408-623-6123. They also specialize in 901 & 915 Transmission Rebuilding.

Good Luck

CrossT · 03-25-2003, 07:08 AM

I am on the verge of needing a new / rebuild 915. I found one dog tooth on the magnet -- and grinding is hard to avoid going into 1st at anything from standstill -- and the trans has 160K on it.

I am considering getting a rebuilt unit from Vertex and having it locally installed by a Porsche repair shop [vs. a rebuild]. I was wondering if anyone has had experience with a rebuilt unit from them. They are listed in Pano for about $1,300 and 'completely rebuilt with warranty'. I assume there is a swap/core charge here.

Opinions on whether this is a good way to go or is a rebuild preferable??

thx,
todd
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86 cpe