Logic for not adding a little STP to the Transmission
 

Other than it won't meet Porsche specs what is the logic not to add a little STP to a 79SC transmission? A VW mechanic suggested it.:confused:

Sometimes the STP will make the gear lube too slippery.
This will make the synchros work harder or not at all (makes the shifting harder).
Bob

I wouldn't risk it. As you know, synchros work on friction. Too much, they wear out, not enough, they just don't grab..and no synchronization....That is why one must be careful that they use the correct lubricant.

Same reason some synthetics won't work well...Porsche baulk-ring syncros especially need a bit of friction to work well. The later ( and more common) Borg-Warner cone style don't seem to suffer as much. More contact area ??

---Wil Ferch

:) Thoughtfull responses, thank you. By the way, the VW mechanic is my brother-in-law. Just wait until the next family get together!:p

OldTee,

I've been using Swepco 201 for the past year with great results. Have you tried it? I haven't used any additives and the shifting has improved noticeably...

I agree with Art, I use swepco 201 for my 79SC. Maybe try some of the swepco.

Old Tee,

What gear lube are you using in your 915 transaxle, and how recently was it changed. Porsche was recommending that the gear oil be changed at every engine oil change back in the '70s. What complaints do you have about your SC's 915?

If your brother-in-law's suggestion was to use heavier gear oil, or along those lines, I suggest flushing the existing gear oil with Valvoline SAE 85W-140 gear oil. If that improves shifting quality, then change it again within 500 miles with the same, or change to Swepco 212.

http://www.pelicanparts.com/cgi-bin/ksearch/pel_search.cgi?command=DWsearch&description=swepco

-Wayne