Is it the synchros?

fastbacker · 10-09-2006, 09:21 PM

The car: 74 911

The symptom: When shifting from 1st to 2nd, the tranny grinds unless you let the revs drop considerably while the clutch is in.

Anyone know if that's a sign it needs 2nd gear synchros?

Thanks-
Craig Backer

Steve@Rennsport · 10-09-2006, 10:43 PM

Craig:

You didn't mention how many miles are on tyour car but that might caused by:

1) Clutch incorrectly adjusted

2) Worn release bearing

3) Worn syncros (and other transmission parts)

4) Wrong gear oil (use Swepco #201)

fastbacker · 10-09-2006, 10:46 PM

I'm unsure of miles. Car is relatively new to my father.

Thanks-
Craig Backer

johnsjmc · 10-10-2006, 05:33 AM

It is common in the 915 trans to have to replace syncros at about 100000 mi +/- They will almost always need the dog teeth replaced on the grinding gear as well as the 1/2 shift slider .I did one 2 years ago and parts will be about $1000. Many people have made big improvements with an oil change and shifter adjustment and /or lived with the wear for a long time by slower shifting.

Motorhead-45 · 10-10-2006, 03:49 PM

If you are unsure of how long it's been since the transmission has had a fluid change this should be near the top of your list for troubleshooting. This seems to be a commonly neglected area when it comes to maintenance. Many recommend Swepco 201. It is not always easy to find though, is more costly (about $45.00 for a gallon) and it's been my experience that the difference between Swepco and a good brand name readily available 80w90 or 75w90 is minimal. Many have claimed that Swepco performed miracles in their transmissions. I suspect in many of those cases the miracle was more a result of conducting a long overdue transmission service rather than a result of using a specific brand.

Driver Ed · Driver Ed's Garage

I'm betting that after you change the fluid, you will still find that there is a problem and that problem will only be solved when you replace the dog teeth (2nd gear synchro).

Motorhead-45 · 10-11-2006, 12:58 PM

If it's never been rebuilt you can bet that everything inside that transmission is tired. I think it's a given that second gear gets more use than any of the other gears and is probably the first to show signs of a tired syncro and worn dog teeth. I'd still change the transmission lube first, make sure everything shift coupler wise is in good shape next and then work on my shifting technique before declaring a rebuild necessary.

I wouldn't take your bet though "Driver Ed"....the odds are in your favor!