Grinding when downshifting into first

[proporsche]

well? i have been telling all my clients, there is no reason to shift in the 1st gear, of course you can ,but if you are going to stop-( not California stops) anyway ..save you 1st gear synchro...and dog teeth...
Ivan

[David Inc.]

Originally Posted by proporsche

well? i have been telling all my clients, there is no reason to shift in the 1st gear, of course you can ,but if you are going to stop-( not California stops) anyway ..save you 1st gear synchro...and dog teeth...
Ivan

Pretty much this. The 915 isn't a modern transmission, it was designed in what...the 60s? Stop before going into first, and if you must go into first at a roll, double-clutch.

[Tinkerer]

I had my 915 done recently and absolutely smooth putting it into 1st on a rolling stop. Before the work it was a double clutch even up shifting to 2nd and 5th was a painfully loud grind.

[ahh911]

915 was rebuilt by reputable local shop 5000 Miles before I picked up the car. It was done ~2014 at a cost of 5000$. I couldn't and still can't shift into first while rolling and must come to a complete stop. What did the shop forget to change/do?


Phil

[proporsche]

Originally Posted by ahh911

915 was rebuilt by reputable local shop 5000 Miles before I picked up the car. It was done ~2014 at a cost of 5000$. I couldn't and still can't shift into first while rolling and must come to a complete stop. What did the shop forget to change/do?


Phil

do you have a list of part being used?Must include 1st synchro plus dog teeth plus sliding ring between 1st and 2nd...
Ivan

[Bill Douglas]

When they did mine, umm, 20 years ago they talked about brake bands and accelerator bands. they said the 1st to 2nd, and 2nd to 1st is tricky because there is the biggest difference in speed (ratios I guess).

I'm thinking it means the next gear has to spin up or down more to match the previous when doing 1st gear shifts.

[proporsche]

Originally Posted by Bill Douglas

When they did mine, umm, 20 years ago they talked about brake bands and accelerator bands. they said the 1st to 2nd, and 2nd to 1st is tricky because there is the biggest difference in speed (ratios I guess).

I'm thinking it means the next gear has to spin up or down more to match the previous when doing 1st gear shifts.

yup Bill..true........... that is why i asked what is on the list...

[David Inc.]

Originally Posted by ahh911

915 was rebuilt by reputable local shop 5000 Miles before I picked up the car. It was done ~2014 at a cost of 5000$. I couldn't and still can't shift into first while rolling and must come to a complete stop. What did the shop forget to change/do?


Phil

Does it grind or does it just not go into gear? Does it help if you double clutch?

[ahh911]

Ivan,
Don't have a parts list.. documentation is lacking.

David Inc,
It primarily doesn't go into gear. If it does go into gear it grabs abruptly with a metal on metal feel, like it's being rotated into position within the gearbox. Maybe like a latch is grabbing feel.

Haven't tried double clutching into first, won't be able to try till the roads are clear.

[David Inc.]

Originally Posted by ahh911

Ivan,
Don't have a parts list.. documentation is lacking.

David Inc,
It primarily doesn't go into gear. If it does go into gear it grabs abruptly with a metal on metal feel, like it's being rotated into position within the gearbox. Maybe like a latch is grabbing feel.

Haven't tried double clutching into first, won't be able to try till the roads are clear.

Yeah it sounds like everything works it's just being told to do something it doesn't want to. It's not a modern Honda six-speed, the 915 takes care. I'd suggest either not going into first while moving or double clutching into first. The 911 is torquey enough that it can handle low speeds in second; first is for getting it moving.

[1QuickS]

Double clutch down-shifting to 1st at low speed is nothing more than shifting to neutral, releasing the clutch to spin the gearbox up and then clutching to shift into first. Although engine/gearbox RPM matching isn't perfect it should be close enough to allow worn synchros to do their job adequately.