prescott

With the recent threads on TBF, I was wondering if super clamps are needed in manual versions of our cars?

My 88 5 speed recently had the clutch replaced along with all the other goodies in there, but I didn't ask the mechanic to check the "clamp".

My TT may need a new bearing soon, so if we go in there, what should a manual owner be doing?

Thanks
Brian

hwyengr

Nope. Super clamp isn't applicable for the manual, because unlike in the automatics, the TT in a manual doesn't exert a force on the crankshaft since it rides in the pilot bearing in the flywheel.

We were just talking about it at the end of the latest TBF thread, but you can put wear on your thrust bearing by riding the clutch, keeping the clutch depressed while stopped, and stepping on the clutch while starting the engine. Whether this is enough wear to cause failure isn't a hard proven (unless you own a Triumph Spitfire...), and your preferences are yours alone.

Jerry Feather

There is no "clamp" in the 5 speed.

the flyin' scotsman

there are indeed clamps on the 5 speed TT.

The rear clamp is integral to the 5 speed transmission with a through bolt that passes a groove in the TT shaft.

The front clamp captures the TT shaft to the stub shaft and is a much longer clamp and correctly positions the stub shaft to the pilot bearing and clutch assembly including the TO brg.

There is no provision for a super clamp but I replaced the shaft (Greg Brown replacement) and brgs (Constantine) as well as new bolts (3) in the respective clamps when the GTS TT was rebuilt.

prescott

Thanks for your responses!

I was going to do the Constantine bearings. Good to know about the new bolts and the GB replacement shaft. I'll have to price those out.

Is the main point of replacing the shaft limited to autos, or are 5 speeds just as prone? I've seen GB's horror photos of disintegrating splines that look like they are out of dragsters, not our cars with "only" 300 hp.

Sorry for the noob questions...I'm still learning about this car!

Jerry Feather

What I said, Malcolm, is that there is no "clamp" in the 5 speed. The "clamp" the OP is talking about checking is the one that needs to be checked in the autos and that is on the front flex plate. There is no front flex plate so the is no "clamp" in the 5 speed.

the flyin' scotsman

no worries.............I replaced the TT shaft as I wanted the rebuild project to be the best quality with the most modern engineering hence the component selection.

The bolts are very reasonable, Gregs shaft is a piece of art and Constantines bearings are so well built they make the OEM pieces appear very weak. I also replaced the stub shaft with another Greg Brown piece.

attached picture (courtesy 928 Int site) is the front clamp between the main TT shaft and stub shaft.

ROG100

TBF has affected 5 speed cars - rare but it does exist.
The front clamps (and I mean the clamp only) is identical the the clamp on the auto cars and uses the exact same pinch bolts.

If the twisting of the Torque shaft effects a auto car it can have the same effect on a manual car. Pushing the crank forward.

Dave928S

+1

Exactly what I have observed. The rear pinch bolt can ride up on the spline and jam/hold the shaft in a forward position, and consequently push the stub shaft into the pilot bearing, which exerts pressure on the end of the crank.

To say there is no clamp is not correct. Correct clamp and shaft location, and correct bolt torque, is just as important on manual cars.

Mrmerlin

FWIW if your just getting into a new 928,
it would be wise to inspect the drive shaft pinch bolts,
this goes for any year and any transmission type.

What is very common is the rear pinch bolt being loose, it happens in any transmission type
this condition lets the drive shaft migrate forward.

The other critical thing for the 5 speed is to have the stub shaft properly positioned.
to do this,
dry fit the stub shaft into the pilot bearing and bolt on the TOB guide collar,,

Push the stub shaft forward till it bottoms out into the pilot bearing,
then slide it rearwards about 3MM.

Then mark the shaft at the rear side of the guide collar, this will make it easy to determine the correct position when fitting the clutch assembly and also to gauge future inspections of the clutch.

Always include a reset of the torque for the rear pinch bolt at the transmission input shaft,
the torque is 66FT/LBS add a dab of blue threadlocker to the threads

SeanR

Correct, instead of 2 pinch bolts you have 3 to check out and there are exactly that many "clamps".

Jerry Feather

The reason I put the word "clamp" in quotations is because that was the one the OP referred to when he says that he forgot to ask his mechanic if he had "checked the 'clamp'." Even he put it in quotations. It is clear to me that he is referring to "the clamp" on the front flex plate that we have all heard so much about. That "clamp" does not exist in the 5 speed. That doesn't say that there are not some "clampS" in the 5 speed--just not the one referred to. Indeed.

GlenL

Yes, there is a clamp in 5-speeds at the end of the torque tube. That's exactly the same place as the clamp that slips and creates TBF in automatics.

OP: No TBF in manuals as there's space between the intermediate shaft and the pilot bearing. Stan gives details on how to ensure this.

Roger, Stan: TBF in manuals? New to me. Looks like something I could perpetrate on myself. Luckily I've got two spare blocks. Planning ahead for this one.