need torque specs - G50 pressure plate to flywheel

[dave harris]

title pretty much says it all! what are the torques specifications for the long hex bolts that hold the ring gear to the pressure plate to the flywheel?

Thanks for the help!

dave

 

[Lynn Larsen]

Stock 911 torque specs are (all clutch since I have book out):

Pressure plate cover bolts.......................25 lbft
Release lever dowel pin...........................8
Release lever ball pin..............................16
Transaxle to engine................................28
​

 

[dave harris]

thanks Lynn!!!

dave

 

[Lynn Larsen]

Dave,

I've got to come clean about something, I got those numbers from a Haynes 911 manual all year - 1989. They have the last chapter for later year model updates, but I just noticed there is not a mention of a G50 or hydraulic clutch anywhere in that book. Before you attach the transaxle to the engine, you might want to verify those numbers. I've been trying to find an online guide, but I am running into the same thing there: all kinds of info for 901 & 915 transaxles, but jack for G50/87-89 stuff.

I hope the numbers are good because they are what I used!

Lynn

 

[dave harris]

Hey Lynn,

that's the same problem I've had - I can't find anything that specifically states it's for the G50!

I've sent an e-mail to DRB to see what they say too - I'll let you know what they respond with

 

[dave harris]

Hey Lynn, got this reply from DRB just now,


We generally use M8 Cap screws x 75 mm long x 9 off, torqued to 30 ft-lbs. Place a very small spot of motor oil on the thread.

so - looks like 30 for me!
dave

 

[Pete T]

This is right out of the factory manual.

slave cylinder 25Nm (18 ft lb)
cross shaft bracket to transmission case 9Nm (80 in lb)
pressure plate 25 Nm (18 ft lb)
transmission to engine 45Nm (32 ft lb)

 

[Lynn Larsen]

Thanks Pete and Dave! Well I am certainly in the ball park and I didn't strip any threads, so I am not going to worry anyway ;-)

 

[jmracecar]

pressure plate 25 Nm (18 ft lb)

Correct, that is what Porsche says, with M8 bolts 8.8 grade. Dry. While you can go higher, that would not be book spec and the bolts may yield. Maybe if you went to 10.9 or 12.9, but that wasn't the question.

If you already torqued them to 25 foot pounds or higher, do yourself a big favor, take them back out, and throw them in the scrap bolt bucket. Get 9 fresh ones and torque them to 18. Then you know they are good to go for a long long time.

While we're at it, Porsche says to tighten each one just a little at a time, and go crosswise, not in sequence around the circle. Once I think they are all torqued, then I go around the circle to confirm it. Sometimes they will cinch up just a bit more depending on the type of clutch & pressure plate being used.

 

[Lynn Larsen]

JMRC,

Would the fact that we are threading into a Kennedy flywheel and not a Porsche flywheel play into that at all?

Thanks,
Lynb

 

[jmracecar]

Hmmm, good question. Porsche OE flywheels are steel...

There's always the old fashioned engineering method. Torque one up gently til it yields, then use 50% or 67% of the value at which it failed ;-)

 

[Lynn Larsen]

Thanks Jerome!

For the new mechanic reading this, JMRacecars recommendation for tightening bolts in a crossing pattern is a VERY good habit to get into. It was one of the very first things I learned when reinstalling the heads on my '53 flat head Ford when I was 16 and I've been using it ever since. When the part is round, like a flywheel or a regular wheel, where you start isn't a big deal, just go to the opposite side on each subsequent bolt. If the part is a rectangle, the general idea is to start in the middle and cross diagonally for each subsequent bolt. Below is a sequence diagram for a Ford 4.6 Mod Motor that gives an idea of what I am saying; although, if you are doing heads, you should always check the sequence for your particular engine. The ideas is that you want the part to lay out smoothly onto is mating surface with no internal stresses from clamping the ends first. (Think of your part as being plastic and determine how you would bolt it on while keeping it as flat to the mating surface as possible.)