1980 SC 915 transmission - where is 3rd?

[grahamkissack]

Recently, my 103,000 mile 1980 SC transmission has started acting up. Shifting into 2nd is getting worse but, more significantly, I mis-shifted into 3rd and ended up with a large grinding noise. I'm finding it harder when I shift up to third to find where it is. I checked the coupler and bushings and everything is tight with little slop. The coupler has not moved and accessing reverse and all other gears are in their usual positions. Any ideas? Thinking John Walker might be rebuilding this soon before I have a catastrophic mis-shift and failure. Thanks.

[gliding_serpent]

Open that puppy up before you regret it and find third in many pieces. Synchros are cheaper than gears.

[Nick Triesch]

Change gear oil and adjust the clutch first....unless you are rich.

[Walt Fricke]

Don't futz around - time to have the box opened up. I bet you'll find that the 3d gear dog teeth are just nubbins, and the engagement sleeve's teeth are pretty worn as well.

[yelcab1]

Originally Posted by Nick Triesch

Change gear oil and adjust the clutch first....unless you are rich.

You are driving a Porsche, you are rich. These used to be $25,000 car, now they are $40,000 cars.

Open that box up, or write a check for $3K.

[Das Schnell Ei]

Third is up by the radio

[Nick Triesch]

Give me a break. Most folks who own an old 3.2 are not rich. Most 3.2 cars that are between a 3 and a 4 car are only worth $18-$25,000. Many of these cars have road rash, original motors and trans and not so perfect paint and interiors . I think that you may be living in a different world than most of us.

[yelcab1]

Originally Posted by Nick Triesch

Give me a break. Most folks who own an old 3.2 are not rich. Most 3.2 cars that are between a 3 and a 4 car are only worth $18-$25,000. Many of these cars have road rash, original motors and trans and not so perfect paint and interiors . I think that you may be living in a different world than most of us.

Two years ago, I would believe you. Right now, when clean SC is going for $25K, clean G50 Carrera is going for $40K, clean 993 are going for $50K, RSA for $180K, 964 are $40K, all used parts and all repairs are also going up.

You are driving one of these cars, you are assumed to be rich.

[Dpmulvan]

Not rich here anyone else?

[Nick Triesch]

yelcab1 you could not be more wrong. Like I said, I think you are living in a different world. Most folks on this site do not have the kind of cars you mentioned. We have SC's and 3.2 cars that are always in a state of some kind of work or repair. That is why we have these cars. An on going never ending hobby! That you can drive. Two of my best friends have these cars and they are not rich. I would agree that perfect air cooled cars will cost a lot. But most of them are far from perfect.

[Josh D]

Originally Posted by Dpmulvan

Not rich here anyone else?

Back on topic.

Like Walt said, likely dog teeth have broken off allowing the syncro band to expand enough to not allow slider to engage third.

Drain the oil and see if you have dog teeth on the magnetic drain plug. You can also remove the shift rod pivot/inspection cover and have a look inside.

[grahamkissack]

Thanks for the input .... a call and email is into John Walker. My bank account isn't going to like this!

[OsoMoore]

Originally Posted by Josh D

Back on topic.

Like Walt said, likely dog teeth have broken off allowing the syncro band to expand enough to not allow slider to engage third.

Drain the oil and see if you have dog teeth on the magnetic drain plug. You can also remove the shift rod pivot/inspection cover and have a look inside.

I had a similar problem after letting someone else drive my SC (not going to make that mistake again!)

The blocks and bands under the 1st gear synchro got jammed and the ring wouldn't compress. This meant I couldn't get into 1st. A few weeks and $900 later, I had it rebuilt with new 1st gear dog teeth, some synchros and a sleeve, and other random parts. You can do it yourself if you have time and determination. But it wasn't easy. Fortunately, 915 transmissions aren't actually that complicated.

[pmax]

Originally Posted by grahamkissack

Recently, my 103,000 mile 1980 SC transmission has started acting up. Shifting into 2nd is getting worse but, more significantly, I mis-shifted into 3rd and ended up with a large grinding noise.

By mis-shifted, do you mean going into the gear with the clutch not fully disengaged or releasing the clutch before the gear is engaged properly ?

Trying to understand the damage mechanics.

[grahamkissack]

PMAX .... no mis-shift. The clutch was depressed properly. When I move the stick to where 3rd is supposed to be sometimes it doesn't find it and I get a large grind of moving gears. So I move the stick slighter further to the right and it works. Never used to do this. I also find the slower I do it the better going into third. 103,000 miles on the tranny which looks unopened so its time.

[Walt Fricke]

Well, the way these transmissions are designed, I'd say the grinding you get sometimes is because you are trying to put it into 1st, and its synchro isn't in very good shape. When you move the lever (back in neutral) over a bit more to the right, you say you can get it into 3d.

There isn't some intermediate position whereby you can cause two gears to try to engage at once (lockouts prevent that, and we'll forget the issues 5/Reverse can present). Either the dongle inside the transmission is in the 1/2 slot, or the 3/4 slot. If it is in between them (which it can be), it can't move anything - pulling back or pushing forward on the lever basically can't be done.

I once shoved so hard trying for 1st when things were in between that I bent one of the engagement slots inside the transmission, which caused all kinds of problems. But no grinding.

The more worn the synchronizing parts are, the slower you need to shift to try to avoid grinding. The real trick is to double clutch, both downshifting, but also upshifting. The upshift double clutch maneuver is simple: clutch in, shift to neutral, clutch out (no reving), clutch back in, shift to next higher gear, clutch out, step on the gas. What this does is give the gears time to slow down some to match the new, lower, engine speed in the higher gear. The opposite of what you do downshifting trying to speed up gears.

I would recommend that you install the Seine gated shifter. You can adjust that so that in neutral ,and without your hand on the shift lever, you will automatically have the lever and its associated gizmos back in the transmission nicely lined up in the 3d/4th plane. Or the Rennshift, or one of the Wevo products, which do the same thing.

Will be interesting to hear what John Walker finds.