915 Opinions needed...and a way late introduction

[shelbypruden]

Hello all,

Ok, this is a way late introduction (I joined the board in 2005), but here goes:

I'm a TN National Guard mechanic who recently returned from a stint in Kuwait and Iraq's deserts. I've been a european car owner (hence wrench turner) all my life. My 1966 6-volt Beetle in high school is indeed what truly taught me to be a mechanic years ago. Of course, for the Army I was repairing Humvee's, ASV's, LMTV's, and HETT's (Small to Large wheeled vehicles).



I got damaged 1968 shell a few years back. However, I had saved a decent chunk of change while I was overseas, with the intent of getting another 911 albeit complete this time.



I searched while deployed and after I got back for a good while. I finally settled on a 1980SC Vern Lyle was selling here on pelican. Vern had only driven the car some 500 miles and needed to sell for personal reasons. This was previously Scott Kaefer's car. Scott had done some mods, made some posts about it (Ruf bumpers, Bilsteins, Wevo Trans and Engine mounts). I did due diligence on the 1980sc. Having a leakdown and compression done both with great numbers. I also fully went over it. I've done some work to it: H1's, Omp steering wheel, built an Ipod interface for the pioneer radio that came with, Optima battery and battery tray rust repair. All in all Vern and Scott had the car fairly sorted.



I had enough money to go with a G50 car but I didn't for 2 reasons: 1. My favorite 911's used 915 tranny's.... IROC RSR's, RS 3.0's, and RSR 3.0's. I wanted the pure undadultered impact bumper torsion bar experience. This ruled out 964's, 87-89 Carrera's and 993's were already out due to price. 2. G50 clutch kits were insane on the price front.

For years I've read Porsche mags, Porsche books, Post's here etc... about the 915 and how it shifts. So I was prepared for a slow funny shifting trans that the Getrag G50 bests in all ways. "A box that requires thought to shift smooth" to paraphrase the British Porsche mags. I am versed with Getrag's and how they shift, my old BMW and my Ex- Girlfriend's boxster had them. They can shift as fast as you can. I expected a 915 to grind if shifted fast.

I've now had the 80SC 3 months. So back to my 915. If I shift too fast, it grinds especially 1st -2nd or 5th-4th. I assume the cross plane delay 2nd-3rd has is enough that 2nd-3rd doesn't grind. Also the car must almost be stopped to get into 1st. I have the box down on how to shift with no grinding. But here is the main issue: when shifting 1st to 2nd, to get it into 2nd there is say a "notch" I must push over to get it to engage. The higher the RPM's the less pronounced this notch is. This "notch" doesn't occur often 3rd-2nd. It has never popped out of gear. However, I have to think about shifting the 915 the whole time. I have never had to do this in a car before. It has not become natural for me.

Questions for those in the know:
1. This "notch" 2nd-3rd...I know its bad I'm guessing at least a syncho ring maybe a syncho hub?
2. What MPH and RPM, should a healthy 915 be able to go 2nd-1st without a grind?
3. Can you guys shift any healthy 915 fast i.e. Getrag fast if not Getrag smooth, without grinding? Is my pre-ownership understanding of the 915 incorrect?
4. Do you guys think about shifting your 915 or is it natural?.
5. Am I just fixated on it, or am in for a full blown rebuild?

I'll guess I should get some local pelican/pca folk to take my car for a spin and get their impression.

TIA,
Shelby

[bourgeois911]

I've heard all of the above about the 915 but truthfully I don't really think about it too much while I'm driving. Maybe I've just got used to how these things work and I guess you can get used to anything. Linkage comes to mind when you mention "notches", I assume you've already peeked at the bushings and ruled them out as a possibility. I'm not mechanically inclined enough to tear into my tranny so maybe I'm just in denial when I find all the "features" of the 915 to be just normal stuff. I just spent 2 weeks installing new chain tensioners (and I'll probably spend an hour after work tonight cleaining the garage floor because I didn't tighten an oil line DOH!) and I'm ready to just drive the thing for a while. I'm sure I'll obsess over every noise I perceive to be new since the tensioner install until I'm convinced that everything is cool, but you're probably right in getting someone else with 911 experience to drive/ride with you and see if what you're experiencing is is whacky or what passes for normal in a 911. I will say that if driving my 911 was like driving any other vehicle I probably wouldn't own the 911.

Thanks for your service to our country!

[javadog]

It sounds like your gearbox has enough issues that a rebuild would be justified. I am not sure what you mean by "notch" but it may be that your synchro parts are worn enough that a shift takes a fair bit of pressure and a fair bit of time. In other words, as you move the lever through the neutral plane, you get to a point of resistance where the lever stops and, even with a decent amount of pressure, the lever stays there for what seems like too much time, until it finally engages the next gear.

As for the 2nd to 1st downshift, these are only needed when coming to a stop and I always double clutch these shifts anyway. I can't think of a situation where I need to downshift to first at anything above a walking pace.

A 915, or any gearbox using the Porsche syncromesh, can be shifted pretty quickly, if the parts are fresh and everything is adjusted correctly.

JR

[Porsche_monkey]

Pull it and rebuild. They are easy to do. Then you will know it 's right, or at least as good as a 915 can be.

[ChkbookMechanic]

Originally Posted by shelbypruden

Questions for those in the know:
1. This "notch" 2nd-3rd...I know its bad I'm guessing at least a syncho ring maybe a syncho hub?
2. What MPH and RPM, should a healthy 915 be able to go 2nd-1st without a grind?
3. Can you guys shift any healthy 915 fast i.e. Getrag fast if not Getrag smooth, without grinding? Is my pre-ownership understanding of the 915 incorrect?
4. Do you guys think about shifting your 915 or is it natural?.
5. Am I just fixated on it, or am in for a full blown rebuild?

I'm not completely in the know, but I can tell you my experience with my 915 transmission...

1. The few 915s that I have test driven and the own that I own don't have this notch on a 2 - 3 shift. I've driven ones where I couldn't get the car into 1st or 2nd gear because the shift coupler and other parts were not aligned correctly.

2. I almost never put the car into 1st unless I'm about to stop but I can put it into 1st pretty reliably around 15 - 20 mph. rpms I don't really know, I never really look at the tach in my car (or the speedo either now that I think about it).

3. I can't slam the gears in the car like I could my previous vehicles (wrx, miata) nor like my DD (m5) but I can shift it fast enough without grinding it.

4. I don't think about shifting the car at all. I just put my hand on the lever and put it into the next gear. Granted, I don't let many other people drive my 911 due to the transmission and clutch being a lot different than modern ones, the lack of a centering spring on the shifter can and probably will throw off some people as to what gear they are going into...

5. I would not do a rebuild until all the other items around the transmission have been checked (the coupler in the back, the clutch wires, etc.) or you are pulling the engine for some reason and the transmission has a lot of miles on it.

[jtfreels]

Hey Shelby,

The only thing I can add is that it took be a bit to get used to shifting. My car has the factory short shift so its a bit different.
My "style" is to pause briefly in neutral before going into the next gear. If I go too fast then it seems to block, which may be what you describe as a notch.

I'm in the Germantown/Collierville area, cars not actually running right now but should be in the next few days, maybe we can get together and compare.

Jay

[Elombard]

I put a fairly fresh rebuilt 915 in a car a few years ago. It shifted fantastic. If you search I think you will see that you cant shift 915s really fast because of the synchro design. However, if all else is working well I think you will not find this as a hindrance even on the track.

I think you should look at the following if you have not already.

1.) Loosen the tranny and motor mounts a couple of turns and re tighten (alignment with linkage).

2.) pull the shifter tower and linkage (behind the seats) all the way apart and make sure every bushing is good. Sounds like the POs probably went with the high performance bushings and I think they wear out after a few years. they are better than stock in IMHO.

3.) Install a FACTORY Short shift if you dont have one.

4.) Use a round (914??) NOT oval bushing in the linkage at the back (between the seats) if you dont have one (read up on this install, easy to break the casting) or buy one of the better universal joint linkages.

5.) Install the neutral spring centering device (cheap) that they sell or maybe get one of the high dollar shifters.

6.) Make sure the linkage is adjusted PERFECTLY, especially with the round bushing in the U-joint.

IN short if you go all plastic bushings, a used short shifter, and a $100 neutral centering thing you will have a couple of hours and maybe $250 into it and it will shift great...unless you have synchro or other issues inside.

If you have the change there is a fantastic tranny in the parts FS section right now. $4K 7:31 R&P LSD etc. You will really enjoy the burst in performance with the 7:31.

I bet if you pull everything in the linkage apart you will find a bad bushing and /or it has slipped out of adjustment.

DOnt forget to check the round bushing that sits behind the shift tower (guides the linkage bar) in the tunnel, it makes a big difference, they fall apart and are hard to see.

[84toy]

A properly built 915 does not have the traits you hear about. The worn ones do. I shift mine into first all the time without a problem in both 911 and 914. In fact I have a regeared 915 in my 914 and first gear is REALLY tall but I frequently shift into first at 30 MPH with no issue or resistance. (not a mis-print)

If you replace dog teeth, syncros and shift sleeve and don't take short cuts to save money you will have a tranny that shifts pretty good. It won't be as good as a borg-warner syncro setup but won't leave you disappointed either. After rebuild, the linkage setup is critical and make sure you replace ALL the bushings.

Good Luck.

[Bill Verburg]

You likely have other mechanical isues, but I found that I could beat even good 915 syncros when the wrong fluid is used.
Don't use any synthetic trans fluid in a 915
Do use a fluid known to be good w/ theses trans, Swepco comes to mind

[db_cooper]

I will second and call on the chair to approve the first step being a change of gear oil to Swepco. Easy to do and once run for awhile may nullify to need for surgery. The stuff is amazing.

[Elombard]

The POs were heavy hitters I bet its already in there.

[RWebb]

easy to check - see what color the fluid is

you cannot beat or force the synchros on a 915 IF it is properly operating

my bet is that it is an instant slower to shift than a G-50

some like the 915 as it feels more vintage -- more mechanical

as it so happens I just started a fun thread on the G50/915 in OT - look for G-50 and "Wankers" - some comments are illuminating, but of course not all

shifting the 915 will become natural after a while - if you are nervous, under stress, etc. it may lose its natural shifting feel even after you "get" it

on my first 911, I discovered that just changing to a different style of **** knob made the trany. really natural feeling and easy to shift(!)

I agree to check fluid, coupler and shifter bushings, adjustments etc. before hauling the thing out.

You may want to modify it for strength if you rebuild it.

[Elombard]

very good point on the knob I think the factory 915 shift knob is the best knob I have ever shifted. IF you dont have the factory hard plastic knob get one.

[shelbypruden]

Thanks guys for all the input. I checked the bushings between the rear seats on the floorboard, they appear to be brand new. No lateral or rotational play at all. They are round in shape.

I noticed a week after I bought the car the 3 allen bolts were loose on the shift tower. I pushed the tower forward and tightened them. I just tried it with tower all the way back, and 1st became harder and 2nd became easier, not much change in the other gears. I then tried it with the shift tower centered. All the gears have a more similar feel now. 2nd is still more "notchy" than the others, but way more similar. The shift tower change of postition, has I assume, a de facto shift linkage adjustment effect.

This were the trouble started. While testing a guy changed lanes fast with out looking. Causing me slam hard on the brakes, and I pulled right. I slowed from 50-5mph so fast, that a 4 wheel smoke bomb went off. Thankfully there was no contact. 2 blocks later the the cloud was still present in the distance. I will say this: This SC has the best brakes of any car I have ever driven. It has Mintex pads. Even better than my EX's 2.7 boxster's 4 pistions with PFC carbon metallic pads. Stopping power to weight is killer. So driving away I get a terrible shake in steering. Way worse on interstate above 60. This arsewhole cause me to flatspot all 4 of my hankook ventus r-s2's. Of course tires are cheaper than body work.

Anyways, now I'm gonna jack it up and see if Scott Kaefer put the purple swepco in it.

Jay, I'm PMing you my number.

[snbush67]

Shelby,

Swepco is Bluish-green. I think if you find something purple in there it could be Royal Purple.

Welcome on board.

Shane

[BGCarrera32]

The only real 915 shift complaint I have is 1st to 2nd when trying to rip away from a stop light. There is that half second pause there that is not as nice as modern Borg-Warner syncho setups. And this is after having rebuilt mine with new syncho rings and brake bands. Learning to properly double clutch and match revs upon down shifting will certainly ease the shifting and increase the life of the gearbox. (Read High Performance Driving by Bob Bondurant for info on double clutching.)

My opinion is 915s are vague boxes that can be made better with patience, they suck for hoodling around town in traffic, on the track I like them- don't be afraid to wind the pee out them as they seem to shift best when they are spinnin'...

I agree with the others here though that you should not be "grinding" any gears per say. I did all the mods and ultimately it took opening up the box which was no big deal.

And thanks for your service in the Guards. My family and I do appreciate your service.

BG

[HarryD]

Thanks for the service. My boss recently finished a 6 month tour in the sandbox.

My current 130,000 + mile 915 had all kinds of issues when I got it (at 116,000 miles). Before you go rebuild, be sure:

1-Bushings are tip top.
2-The linkage is adjusted properly;
3-Your clutch cable/bowden tube is in excellent condition and installed properly; and
4-Your Clutch is not worn and adjusted properly.

I thiught I was going to need a rebuild whenI first got my car. Once these items were addressed and I use a gentle touch when shifting (three finger tips), I have had no issues unless I try to rush a shift.

[RoninLB]

I've been driving all kinds of manual boxes on cars and trucks from back before they came with syncros.

only what I see in the 915



it's a bastard race tranny
it's not street driving friendly
it was meant to be shifted only above 3,500 without it being work taking care of it
it needs routine internal maintence when street driven
Swepco must be used



I had a choice of a G-50 or getting my 915 seriously fully rebuilt. I chose the 915, wevo internals, externals, coupler, & shifter. No more mystery working the gears. It's as accurate as Robin Hood and just feels solid and confident. It's still a 915 with its quirks that makes it not as mindless and every other street manual box. 1st gear is still a pain but it turned out to be a very satisfying tranny. I maxed out a street 915 and it was well worth it.


you need routine internal maintence, and maybe a wevo shifter and coupler.
.......... or just deal with what you have and save the $2,000.


happy trails

[PcarPhil]

Originally Posted by shelbypruden

I searched while deployed and after I got back for a good while. I finally settled on a 1980SC Vern Lyle was selling here on pelican. Vern had only driven the car some 500 miles and needed to sell for personal reasons. This was previously Scott Kaefer's car. Scott had done some mods, made some posts about it (Ruf bumpers, Bilsteins, Wevo Trans and Engine mounts). I did due diligence on the 1980sc. Having a leakdown and compression done both with great numbers. I also fully went over it. I've done some work to it: H1's, Omp steering wheel, built an Ipod interface for the pioneer radio that came with, Optima battery and battery tray rust repair. All in all Vern and Scott had the car fairly sorted.



I had enough money to go with a G50 car but I didn't for 2 reasons: 1. My favorite 911's used 915 tranny's.... IROC RSR's, RS 3.0's, and RSR 3.0's. I wanted the pure undadultered impact bumper torsion bar experience. This ruled out 964's, 87-89 Carrera's and 993's were already out due to price. 2. G50 clutch kits were insane on the price front.

For years I've read Porsche mags, Porsche books, Post's here etc... about the 915 and how it shifts. So I was prepared for a slow funny shifting trans that the Getrag G50 bests in all ways. "A box that requires thought to shift smooth" to paraphrase the British Porsche mags. I am versed with Getrag's and how they shift, my old BMW and my Ex- Girlfriend's boxster had them. They can shift as fast as you can. I expected a 915 to grind if shifted fast.

I've now had the 80SC 3 months. So back to my 915. If I shift too fast, it grinds especially 1st -2nd or 5th-4th. I assume the cross plane delay 2nd-3rd has is enough that 2nd-3rd doesn't grind. Also the car must almost be stopped to get into 1st. I have the box down on how to shift with no grinding. But here is the main issue: when shifting 1st to 2nd, to get it into 2nd there is say a "notch" I must push over to get it to engage. The higher the RPM's the less pronounced this notch is. This "notch" doesn't occur often 3rd-2nd. It has never popped out of gear. However, I have to think about shifting the 915 the whole time. I have never had to do this in a car before. It has not become natural for me.

Questions for those in the know:
1. This "notch" 2nd-3rd...I know its bad I'm guessing at least a syncho ring maybe a syncho hub?
2. What MPH and RPM, should a healthy 915 be able to go 2nd-1st without a grind?
3. Can you guys shift any healthy 915 fast i.e. Getrag fast if not Getrag smooth, without grinding? Is my pre-ownership understanding of the 915 incorrect?
4. Do you guys think about shifting your 915 or is it natural?.
5. Am I just fixated on it, or am in for a full blown rebuild?

I'll guess I should get some local pelican/pca folk to take my car for a spin and get their impression.

TIA,
Shelby

My old car! That's a great car. The reason I sold it was to help fund my current project. The 2 owners before me are also Pelicans (the PO before me was the one who rebuilt the suspension).

If I were you I wouldn't be in a hurry to rebuild the trans. It shifted great the whole time I owned the car and when I sold it to Vern. No gear crunching or hangups anywhere.

First thing I would do is spend some time adjusting the shifter linkage and swap out the Swepco for fresh Swepco. I was running a Rennshift shifter and Stomski-style coupler while I owned it. Vern wanted the stock parts so that was installed before it was sold. I installed the shifter and adjusted the linkage but it may need to be dialed in some more. If he only drove it 500 miles then chances are the linkage still needs to be fine tuned.

Also I would check the clutch adjustment. If anything I believe the clutch may be about due for replacement as it's been in there quite a long time.

Finally - I don't know how fast you're trying to shift the trans. The 915 trans is not meant to be speed shifted. It requires a somewhat intentional 'pause' in between gears while shifting. Are there any local Pelicans that could drive the car and see what they think about the smoothness of the trans?

Good luck with the car!