Question is......
Is this common in bolts that have been previously torqued to the same specs to fail at a lesser amount of torque???
Tony in Vegas
Tony,
The Specifications Booklet says:
Torque Specifications - manual transmission, shift actuator and central tube P. 46 & P. 47
Central tube/transmission M 10 x 1.5 43 ft/lb
Central tube/clutch housing M 10 x 1.5 32 ft/lb
Oops!
Not too surprising that they failed at 65 ft/lbs!
Wally Plumley
928 Specialists
RUT ROH!!!
ok ..ok..
hmmmmmmm..pg 37-122 "REMOVING and INSTALLING TRANSMISSION" of my fiche manuals say ...
step 1...2...yadda yadda
"3) Install and slightly tighten accessable bolts on central tube flange"
...4...
"5) Lower transmission only far enough that remaining bolts can be screwed in central tube flange (tightening torque 120Nm/87 ftlbs)"
6....7....8....9...10...11...12....
"13) mount transmission on cross member (tightening torque 85Nm/61ftlbs)"
while we are on the subject...how a bout a run down/verification of some numbers for me
Flywheel to fwd flexplate (6 bolts)...?????
Torque converter to rear flexplate (6 bolts)....???
Tranny to crossmember......see above 85nm/61ft lbs????
Rear crossmember to the body/frame...????
Thanx for the heads up Wally......if your numbers are correct I'm glad i didnt strip the threads on the tube flange!! Thankfully it is hardend steel and i was watching and gently turning the bolts as i went. I was leary of the torque values from the "get go"....however, they sure were difficult to get undone when i started all this!!
The bolt size is correct in what you say..10x1.5...as i just went to replace them...i guess the torque values are in question?
Adam B...you out there?
Tony
Yep, that's what my manual says, also. But - the tech spec booklet says 58Nm/43 ft/lbs. Quite a difference. Perhaps the deciding vote comes from the engine torque specs - any M10 fastener (we are talking fastener diameter here, not head size) not otherwise specified torques to 29 -33 ft/lbs. I don't think that an M10 will ever stand 87 ft/lbs.
>while we are on the subject...how a bout a run down/verification of some
>numbers for me
>
>Flywheel to fwd flexplate (6 bolts)...?????
>Torque converter to rear flexplate (6 bolts)....???
>Tranny to crossmember......see above 85nm/61ft lbs????
>Rear crossmember to the body/frame...????
From the spec booklet:
Driver plate to torque converter - M8 - 46Nm/34 ft/lb
Wally Plumley
928 Specialists
Hey Tony,
Got your original email at my office today, had to go out this evening, but as soon as I got home (about 1/2 hour ago) I started digging through the manuals for answers. Chasing down torque specs easily was the most time consuming part of the TT replacement for me. The following are the torque specs I used, indicated by Volume #, Page #, Bolt #, and torque in ft./lbs.
6 bolts, front flex plate to flywheel- Vol II, 39-48, #1 24-29 ft lbs.
6 bolts, rear flex plate to flywheel - Vol III, 37-138, #22 34 ft. lbs.
TT flange to tranny - Vol III, 37-122 Para.5 87 ft. lbs. (yes mine went to 87)
TT flange to front bell housing, Vol II, 39-48 #9 29-34 ft lbs.
Pinch bolts front and rear - Vol II 39-48 #3 & #12 59 ft lbs. + 10%=66ft lbs.
I would carefully follow Vol III 37-123 "Adjusting Transmission Suspension".
When I took mine apart I only found a shim on one side. Fixing what wasn't broke, I shimmed both sides and the tranny ended up banging against the cross member when I would hit square edge bumps. I went back to the original set up and the same happened. I double shimmed both sides and every thing is fine.
I don't know what to tell you regarding the rear flange bolts. It did seem strange to me that the rear bell housing would be cranked down so much tighter than the front, but I figured that was one of those "Porsche-isms" that shouldn't be questioned. I might add that when ever I assemble bolts to be torqued down, I always put a minute drop of oil on the threads to ease entry. Don't know if it's acceptable practice, but I'm sure it's saved me stripping out threads on numerous occasions. It's good that you caught it when you did, I'd go with the lower torque value since you have Wally's blessing on it.
On the rear cross member to the shark body, my shark had some copper shimsthat were sandwiched between the cross member and the body. I thought this was strange, and tried to reinstall the crossmember without them just to see what would happen. The bolts would not torque to spec. I reinstalled them and had no problem torquing them down. For the life of me I can't find the torque spec, but I'll keep looking. I seem to recall having to go beyond the two Transmission manuals to get all the info, so I'll keep looking for you.
Hang in there Tony, you're definitely on the downhill side of this project.
-Adam
Thnx Adam for the heads up AGAIN...i think this is where i was mentioning that before i mount the tranny i will temporaryily torque down the front pinch bolt to prevent the shaft being pushed forward by the tranny installation (the tube is already against the fwd bell housing). Any movement that does occur SHOULD be very small and be caused be the forward flexplate flexing a bit as it is all pushed on and it should return to a fairly "normal" postion after it is on. Hoopefully it will slide on just as easy as the fwd one did. I used a bit of Silicone spray on the shaft to make it slide easier. It will dry up and evaptorate in a short time I'm sure. This should keep me in the GOOD. What i have done is MARKED the splined shaft at the fwd collar as it sits NOW, hopefully in perfect postion (2mm shows at the rear end)and ZERO preload on the fwd flexplate/crankshaft. This way i will have a reference every time i go to check for movement.
I believe you or someone mentioned something about prying the flywheel aft THEN tightening all the pinch collars down when it coems to the final installation settings??
Tony
Nasty thing is though Adam, the bolts at the rear go into an ALUMINUM thread, not steal like the ones up front! Would suck to strip eiter end but the odds are if its going to happen it will be at the rear flange where the bolts pass through the tube and into the aluminum rear bell housing!
Hence the reasons i want to get these numbers all figured out and im bugging you all!
I also got the tube mounted to the front flange with out managing to have the darn shaft slide inside the tube itself. I came up with the idea of putting a pair of vice grips around the shaft...then another pair of grips anchoring that pair of grips to the tube itself! Inother words the shaft became temporarily anchored to the tube as i slid it in! it went all they way but a 1/2 inch as the grips were in they way. I removed the grips and the tube/shaft slid easily in the rest of the way!
2mm at the end on the way in...and now 2mm secured!
If i recall you ended up knocking your shaft throught the tube a bit to far?
correct?
Tony..learning from adams boo boo! : )
Actually, adjusting the shaft in the tube to get the 2mm out front went smoothly. Mounting the front flange to the bell housing wasn't where I made my mess up. I pushed the shaft through the tube when I went to mount the tranny to the rear of the torque tube after the front had been mounted.
The rear hub was too tight. When I pulled the tranny onto the drive shaft, the shaft only went about an inch into the rear hub leaving about a 2" gap between the rear flange and the converter housing. I got some extra long bolts for the rear flange, and threaded them into the converter housing. I then cranked them down to suck the tranny up to the rear TT flange. The bolts cranked down pretty easily, and I just assumed that the drive shaft was being pulled into the rear hub. WRONG. The rear hub was pushing the drive shaft out the front of the tube.
Don't let this happen to you. If there is any gap between the converter housing and the rear flange when you go to crank down on the rear flange bolts, keep a close eye on the drive shaft to make sure it isn't moving forward as you crank down on the bolts. If there is any movement, you've got to pull the tube, remeasure the 2mm, and go at it again. I ended up torquing the whole rear assembly (rear pinch bolt and converter housing) to the rear flange with the tube outside the car. I had to wedge the chuck jaws of the rear hub open over night to loosen them, and had to use a rubber mallet to get the rear hub all the way onto the drive shaft. Definitely not the way the manuals shows how to do it, but it worked!
-Adam
>TT flange to tranny - Vol III, 37-122 Para.5 87 ft. lbs. (yes mine went to 87)
>TT flange to front bell housing, Vol II, 39-48 #9 29-34 ft lbs.
Ah hah!! i think i just realized my BOO BOO...or as Wally put it, my "oops"
there are 2 diferent torque values for the front(34) and rear(87) attatchment points! Hence the bolts in the rear flange/tranny connection are THICKER than the ones in front!!
now its clear why the one twisted on me!
Figures they would place the bolts with the highest torque value in the hardest spot to reach! on top of the rear of the tube!!!
thnx adam and wally
Tony