Yet another tranny diagnosis

[lally911]

Can the tranny gurus please take a quick look and tell me what you see. Symptoms were frequent grinding when shifting from 2nd to first Had to come to complete stop, double clutch then shift into first. Even with that it would occasionally grind a bit. Shifting from first to second was also getting tough. The engine and tranny were out so thought I'd take the opportunity to dive in and learn about the tranny. Here is first - looks like the synchro is well worn and the dog teeth are a bit rounded off.



And here is second. The dog teeth look ok to me but again, the synchro looks quite worn.



Thanks for any help.

Keith
85 911 Coupe

[Jim Sims]

This past winter a friend and I did an "economy rebuild" of a '73 915 as an experiment. We only replaced the synchro rings (1-5) and brake bands (1-5), a one needle bearing with a fractured cage (in three pieces) and some thrust washers. The dog teeth looked about like yours; upon reassembly and installation the transmission worked just fine and thus far we haven't heard any negative reports on it. It depends what your time is worth and if you want to go back in sometime in the future but an economy rebuild is less than $500 in parts and one where the 1st and 2nd dog teeth, 1/2 operating sleeve and spider are replaced will likely be over $1200 in parts. 915 parts are becoming so expensive that they are changing the labor versus new parts equation.

[ed martin]

I had a long standing problem with getting into first gear. That is I couldn't get into first gear at all unless I was at a complete stop. So my original intent was to simply replace first gear syncro. Once I had the transmission out I realized that my first gear dog teeth were completely shot. Also my syncro bands looked worn as well. I removed the first and second syncro hubs and took them down to Robert at Dutch Treat, a mechanic here in the south bay area with a very good reputation. He was saying that not only were the first gear dog teeth completely shot, which was quite obvious, but also my second gear dog teeth were a bit worn. I would say that my second gear dog teeth were in better shape than the ones you have pictured. Robert pointed out to me that the points on the dog teeth should be sharp and crisp, with no rounding. The pointed edges on the slider should be the same way. I sort of protested thinking that the teeth appeared to be good enough. He convinced me in the end to install brand new componants throughout first and second, that is new dog teeth and syncro bands.

When I finished the job, I was very pleased with first and second.
When driving I just can't shift into first and second enough times. The only problem that I have now is that first and second are so smooth that my third gear is now noticeably flawed. It grinds a bit intermittently. If Robert had seen those dog teeth he probably would have talked me into changing those as well, but he never saw them.

By the way it looks to me that somebody has already addressed your syncro problems by flipping them over, engaging the unworn side with the dog teeth. That's the way it looks to me. Maybe John Walker will respond here and give you a definitive answer.

[lally911]

Thanks for the info. Comparing my parts to the pictures of the new parts in the other recent diagnosis thread was also helpful. Looks like I'll be spending a bit more than originally planned.

[lally911]

Spoke with John at Pelican and now have these part numbers for all the brake band pieces.

1st
brake band - 915-302-316-01 - $5.12
thrust block - 915-302-321-00 - $20.80
anchor - 928-302-321-00 - $11.50
double brake band - 928-302-319-08 - $25.25

2nd
brake band 915-302-316-01 - $5.12
thrust block - 915-302-321-00 - $20.80
anchor - 928-302-322-00 - $18.32
double brake band - 928-302-318-02 - $31.98

3rd, 4th, 5th
brake band - 911-302-316-08 - $11.33
thrust block - 911-302-315-00 - $4.70 - special order non-returnable
anchor - 911-302-317-01 - $9.17

Dumb question though ... what is the difference between the brake band and the double brake band for first and second? I took those gears apart and only found a brake band, anchor, and thrust block. What am I missing here? Where does the second brake band go?

[Jim Sims]

1st and 2nd in early versions contained one or two smaller separate brake bands. A double brake band (which you show in your image) is a single piece; what used to be two brake bands in connected into a whole by a small link of metal that the anchor block pivots over. Jim

[lally911]

Thanks Jim, that explains it.