heinrich

I'm turning against the NEW Mobil One synth. I swapped out OLD M1 for NEW M1 and made a MASSIVE difference in the negative. (gearbox that is).

FlyingDog

Same here. I could either use 2-4 or 1-3-5, but could not go odd to even or even to odd.

I changed the diff and transfer case oil in my Jeep to RP and mileage appeared to improve and transfer case noise decreased. My 928 tranny has Redline in it now, but I will try RP when it's time to change again.

Marine Blue

I haven't noticed any issues with the new M1 although I haven't had it in the car very long either. Can you better describe your observations and did you change viscosities?

bronto

Well, my wrench looked at the clutch a little over a year ago and he said there was plenty of meat on it. And I'm not rough on my clutch. Part of the servicing he did on it (along with the RP swap) was replacing the hydraulics - including clutch master cylinder. And it wasn't this bad prior to servicing. Which is why I'm thinking something's out of whack.

largecar379

I run Royal Purple in everything I own (except my Peterbilts).

there offices are two minutes from my house.....nice to be able to support the local folks.

--Russ

hacker-pschorr

Welcome to the world of the 928 double disc clutch. With a duel disc and 220hp the friction discs last a very long time Unless it's adjusted wrong). Anyone who says the double disc is a POS has no clue how to adjust one.
No offense to your wrench, if there is a shifting problem on an early 928 that could be a clutch issue and they look at the friction discs......they do not have much experience with these drivetrains.

Sit back, grab a beer and read through these threads:

Pat 1
https://rennlist.com/forums/showthread.php?t=268926

Part 2
https://rennlist.com/forums/showthread.php?t=273590

Part 3 - the fix was finally found
https://rennlist.com/forums/showthre...ghlight=clutch


Long story short since I'm such a nice guy. The release bearing guide tooth broke and was moving on it's own. We are talking about movement that is only a few millimeters. This was enough to push the intermediate disc out of alignment causing a very random shifting issue. The only way this was discovered was 100% dissasembly of the clutch.

bronto

Wow, seventeen pages of messages. Can you give be a brief synopsis? I'm heading over to the garage at noon (PST) for other reasons, and I'll ask him about it. He has been a Porsche mechanic since 1978, factory trained on the 928 in 1979. I have a lot of confidence in him based on his accurate diagnosis' in the past. I just want to know what the heck I'm talking about. A P.O.'s wrench botched a clutch job - and Peter caught it before serious damage was done - so I'm thinking that this is either consequences of that botch, or an adjustment of some kind needed because of the hydraulics work.

hacker-pschorr

Double disc possible known issues:

1. air in the system - not as easy of a fix as it should be.
2. intermediate disc is bad. Firction surface will be perfect, the "springs" that hold it's alignment wear out. This is a royal bitch to diagnose
3. In the case of my car, the release bearing was broken. Not in the normal way - pictures in the last two posts I linked to
4. Guide shaft is dirty / warn causing the friction discs to hand up
5. Pilot bearing is sticking
6. Friction discs are worn
7. Master and / or slave are no longer working as intended
8. Ball cup for the guide fork is worn or missing
9. Ball the cup rides on has backed out of his home
10. Clutch fork is bent - very rare, not even sure how it happens
11. I'm forgetting something.....

BrianG

I put it in the gearbox of my GT to see if it affected the typical cold notchiness. No difference noted hot or cold.......

FlyingDog

Mine was all of the above.

mark kibort

swepco can help the early transmissions with the problems being discussed here. It was a big improvement for me when i ran the early gear box with my 84.

with the S4, ive been pretty happy with the redline products. 75-90 NS mix with non NS

RP sounds good. probably right up there with redline and amsoil. (although ive been running only amzoil since ive started racing the holbert car 6 years ago , and 91 race days. kind of tough to change something after this kind of a run !

Mk

bronto

This, in fact, was what I was worried about.

He was last in the clutch when I reported that the clutch action wasn't smooth. He found that the previous clutch job was botched; there was a plate on backwards, bolts weren't torqued and the shaft wasn't greased. He fixed everything back up and inspected everything, and he said that he didn't see any serious damage but that my next clutch job was going to be expensive because the shaft would need to be replaced.

Still, this wasn't such a problem prior to the RP swap and hydraulics work.

FlyingDog

Early intermediate shafts are not nickle plated like later. They drag more and wear out more easily.

928autobahndreamer

Does the new Mobil 1 formulation have adequate zinc levels to protect the flat surfaces? I had heard that this is why many older engines are having problems with the newer synthetic oils. If Mobil 1 is no longer good protection, I'm guessing that Red Line, Royal Purple and Amsoil do have adequate zinc additives?

I guess I could go back and search all 5,000 pages of previous oil posts, but I figured it would just be easier to ask.

bronto

Solved! It was the Forward Shift Ball Socket. The cup was completely thrashed. Socket replaced, shifts easily now. Inthe interim, however, we changed out the Royal Purple to standard oil with LSD modifier. The RP is rebottled, maybe I'll put it back in someday. Any reason not to put it back in? It was only in use for about 2 months, maybe 1500 miles tops.