Q – Last year I bought an ’81 911SC that had 8 broken Divalar head studs. I went through the engine myself and had a mechanic that worked for a Porsche dealer in the past go through the transmission. He put in new syncros on all gears and new drive dogs on 1st and 2nd. Everything is back together and running but I am having a couple of issues with the trans.
When trying to put the trans into first gear while at a dead stop it is common for it to not go into gear and other times it just falls right in. If it does not go in I will let the clutch out depress clutch and try a second time, may need to repeat a couple of times and it will go in. Shifting into second (up shift) sometimes goes in good sometimes not. Down shifting into second you can very distinctly hear the small whine that goes with a syncro getting pressure put on it and again sometimes falls right in and other it takes a fair amount of muscle to get it in gear.
At this point, I’ve put in about 500 road miles on the rebuild, and only third, fourth and fifth behave as they should. I have rebuilt all of the shifter linkages and have set the shifter coupling so that 3rd and 4th go into gear just to the left of the 5th / reverse gate. I changed the gear oil and found the oil to be dirty, what I think is a normal amount of metallic “mud” on the magnetic drain plug and a few shiny metal fines. I then tried a different gear lube with no apparent change. After initial clutch adjustment, still encountering the hard shifting on first and second gear; I set the clutch a little on the high pedal side to ensure it released. This produced no change. Both conditions seem to be worse when trans is warm.
The guy that went thru the trans said I should give it some time and see if it gets better. If not he will go thru it again but said I would need to buy OEM sycros for first and second instead of the aftermarket ones I provided from Pelican parts. He said if the problem is not corrected by this, he’d blame the syncros. I wouldn’t try to tell him, “The Master Cylinder told me…”, but I am looking for somebody with more expertise than I to tell me if this sounds right. The thing I find odd is the problem in 1st and 2nd, given that those are the two gears that recieved new drive dogs.
Help! – Terry
A – I hate to tell you this but it sounds like it may have to come apart again. It sounds as if you have done everything externally that you can do.
The syncro whining you describe could be caused by a clutch that is failing to disengage. I have heard it before, many times, so that would be my bet. I think it odd that you would be seeing mud or metallic filings in the oil after a rebuild but I suppose it depends on the method and depth of cleaning.
You need to get a second, hands on, opinion before pulling the trigger. I would suggest that you take the car to an independent tech who has decades of experience with older cars (with all due respect to the guy who built it). Again, although it sounds like a clutch issue rather than a trans issue, I would need to experience it to speak intelligently about it.
I do not think the syncro origin is a likely factor although aftermarket parts are sometimes not the bargain they appear to be. I also suggest that next time you farm a portion of the work out, let the tech source the parts. You usually don’t save enough money to offset the diffusion of warranty responsibility, especially on a huge job like this. MC