slate blue

Hi to all, I was wondering what you'll thought about an article I read on a Australian website. Does the change to a early type sliding shaft torque tube offer a solution to high horsepowered automatics? Your opinions please.

The coupling point is between the Torque tube and the Transmission. The article is by Bruce Buchanan
and starts below.

This applies to both manual and automatic transmissions. From 1984, when the four-speed automatic transmission was introduced, there was a change. Whereas on the three-speed auto a male shaft came out o the trans/ torque converter housing area and connected to the torque tube shaft via a sliding sleeve, very similar to the sliding sleeve on the manual cars at the clutch end … on the four-speed it’s a female shaft and no sliding sleeve. This has the usual clamp around it, and it’s just one hex bolt.

Again, if the car is driven hard (e.g. fast acceleration), the bolt in this case will stretch ever so slightly causing less clamping force, which causes the spline inner and outer to chatter and move. This in turn will allow the torque tube shaft to move slightly forward and more importantly, will eventually either damage the spline on the torque tube shaft and/or crack and break the hollow female shaft coming out of the transmission. (both manual and auto).

This is expensive and avoidable

<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

John Struthers

GG,
Sounds like you are describing the
demise of Mike H. . In his recent post
his TT apparently lost the battle some time
ago and finally gave up the ghost from
the inside out. Curious as to wether this
was spline land and groove failure 'only'.
Or, was there bearing failure involved.
I was wondering about this for a while,
and mentioned it to Jay Wellwood in the
'stroker crank post'. As HP goes up what
happens to various pieces of the car
-drive train- as new/greater stresses are applied. I was hoping some of the Club/sport racers could shed some light on what
new failures to expect at the new
torque and HP levels. I am particularly interested in the TT, TC, and both 3 and
4 spd Auto transmissions. The half shafts
could be a point of interest too as related
to wheel/tire dimensions which magically
increase in size with HP gains and racing.
In any case Jay mentioned the slider yoke
found on most American made RWD cars.
All shark owners have a vested interest in
Torque Converter balloning as that is
described as the primary cause of the
crank shifting forward and turning the
crank journals into lathe tools that shave
the main journals/bosses into ruined,
displaced metal. TT is expensive but
a new short block is truly dear. 'Snow' was wondering a while back if there was some
way to add a second bolt and or machine a set with two opposing flats with bolts.
Good post, I'm still waiting for the racing guru's to shed some light on this.
Those who flog these machines should have
some insight and wisdom to offer.
John S. & Pattycakes <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

lobis

When the TT moves forward doesnt it put more pressure on the thrust bearing(move it forward to much?) and cause all hell to break lose inside the motor?

928 U.K.

hi

loctite is supposed to be good to use when replacing the bolts to stop them rattling free and you should always use new bolts

i am putting my 4 speed box back in soon as it is being rebuilt at the moment

cheers

Tim 84 s2 auto

show'n'go

[quote]Originally posted by John Struthers:
<strong>All shark owners have a vested interest in
Torque Converter balloning as that is
described as the primary cause of the
crank shifting forward and turning the
crank journals into lathe tools that shave
the main journals/bosses into ruined,
displaced metal.</strong><hr></blockquote>
Well, maybe all shark owners with an AUTOMATIC transmission....
I *did* post a reply to your query in the "stroker crankshaft" thread regarding this John.
You won't get much feedback from track junkies on this one, most serious track guys run 5 speed cars. I'm only aware of two "purpose-built" track cars that run automatic transmissions. One of them is owned by Constantine in Florida, and I know he has been doing some custom machining work to incorporate a coupler that he hopes won't potentially destroy the thrust surface in the block. I'm not exactly sure of the details of his setup, but I believe it has a "sliding spline" design.

Brad
'78 <a href="http://www.p-caronline.com/directory/showngo/" target="_blank">928 euro</a> 5 speed
928 Owners Club

Erik - Denmark

I am wondering about this ballooning discussion

Up to 1985 model the shop manual describe a procedure for a preload of the axial pressure on the crankshaft 'measure X' = 0.3 + 0.2 mm - Manual II page 39-51 (3 speed auto)

In manual III page 39-137/138 (4 speed auto) the same distance washers are shown, but marked with * and a note telling that these are deleted from model 1985

Then the difference of the TT shaft and the intermediate TC shaft - In practice (regarding axial pressure) there are no change - In the 'newer' version the rear clamp is 'built-in' to the intermediate TC shaft - I.e. on bough models there are a fixed connection from the TC shaft to the front three-angel flange when the clamp bolts are tightened!!!

Then to my questions:
1. Is this 'X' measure still actual on 3 speed auto - up to 1983?
2. If yes, what then to do with on 4 speed auto model 1984
3. For models 1985 and forwards X distance is not actual - Can someone tell me, why Porsche has changed this procedure, and what is the correct procedure for the different models?

jpitman

I'm not sure I understand what people think goes on with the TT shaft etc.
For one thing, my 83 Euro (3 speed box) has clamps at both ends of the shaft (seen the front one, undone the lock bolt on the rear clamp), which doesnt seem to fit with the Buchanan description of it being a slide joint somehwer there.
Ballooning of the TC - I can visualize this happening when you put 300ft-lbs into it, but what effect does it have? Correct me if I'm wrong, but... the TC is bolted to a flex plate which is mounted on a shaft on two bearings in the front TC cover - this shaft is clamped to the incoming TT shaft; the rear of the TC is on the greabox input shaft. I wouldnt expect the front cover shaft to have much if any axial play, unless the ballooning distorts the front cover - even if it did this , this would push the whole TT casing and angine forward, so there shouldnt be any relative (to the engine)movement of the TT shaft forward? Is the ballooning pushing back against the front cover of the main box, then pressin the front TC cover? - same result as above, no relative shaft movement.
If the TC ballooning is radial, outwards (not axial), what will this do? Will it pull the shaft backwards, tending to pull it out of the clamps, and when relaxed, there is more shaft exposed, thus pressing forward against the engine thrust bearing? This is a bit like the observed results, but???
Anyway, if the 5 speeds have a sliding spline that carries all the power, why the !@#$%^&* cant the autos be built with a similar fitting? I have seen a clutch set up in pieces, but I understand there is a short shaft like a normal gearbox primary shaft, piloted in the back of the crank, splined through the clucth plate(s), and then clamped to the main TT shaft. Why couldnt you fit a 5 speed flywheel (lightened extensively?) with a clutch plate(s), short shaft, clamp, and then modify an auto TT and shaft so it could clamp with the short 5 speed shaft? Or modify a 5 speed TT at the rear to mate with an auto casing, leaving all the 5 speed fitting at the front, (without a clutch slave)? I dont understand why the autos have to have a clamped connection (ie non-sliding), when the 5 speeds transmit the same power on a sliding connection.
Anybody.....
jp

Erik - Denmark

JP,
Good points! - Looking forwards to hear the real answer from the 928 experts

John Struthers

JP, Show, Erik,
Good points, but its 1:20 am here and I'm sleepy.
Been thinking about the drive plate myself if that was your point. I'm not sure if there is enough room -internally- for the splines to move around at the drive plate on one side and/or the converter drive flange on the other, safety slop.
But they are bolted up tight on either end and I can't just attrubute the crank 'walk'to anything but an outside force. I'm assuming bolt up is necessary for bearing surface contact. right?
There was an earlier post that mentioned a combo of TC balloning and TT twist under load. I think if someone (don't look at me!) was power braking without preloading -creep before full brake- you could induce, over time, a weak /beercan condition on the TC but it wouldn't be uniform so there should be a thumping/bearing problem well before things got to far out of hand .
Show, sorry. Thanks for the obvious spanking on the racer side, sheesh, I am a slovenly auto user.
Forgot all about the stick people
Erik, Perhaps Steve C. or Wally can sort out the X values...it does appear as though something is amiss here...failing that it might have been corrected in a shop bulletin(TB).
JP, for those guy's to come up with a lamp control unit that tells me a marker light is out but don't have a 'simple' shock absorbing close tolerance coupler in the drive train or failing that. Something to prevent fore and aft crank walk, is beyond me. Then again this could all be hindsight if weren't for the fact that the clamp IS THERE FOR SOME DAMN REASON! Hell, maybe someday it will all be explained to us on the History Channel.
Night...