Porsche 928 Torque Tube Rebuild Procedure
by David E. Lomas
Intro to the Guide:
*NOTE* - This process assumes that you have the rear suspension, transmission, and exhaust removed from the car to be able to get access to the torque tube. This is a guide on the rebuild of the torque tube.
This is based on my experience with an 86.5 automatic transmission 928S. Your application may vary depending on model year and transmission type. This is intended to be used as a guideline only and not to be taken as gospel. If you have different experiences in your rebuild, please forward them to me to be included with this text. I can be reached directly at ketchmi@hotmail.com .
A quick word on transmission and torque tube removal. I decided to remove mine as a unit, instead of dismantling them underneath the car. If you have access to a lift, you may want to dismantle them. As I used jack-stands and hand-tools, I felt it would be easier to remove it all from the car, then dismantle and repair it. It can be done in your own garage and help was only required to re-install the unit and rear suspension.
Once you have the torque tube out you will see just how easy this really is. I had been told that automatics had 2 bearings while 5-speeds had three. My automatic had three, go figure.
You must remove the bearings from the front of the torque tube. There is a harmonic dampener installed in the rear, and I decided not to disturb it. The bearings are suspended in a plastic/metal carrier that is friction fit in the main tube. There is also a plastic/metal insert in the bearings that you will need to reuse. It provides a friction fit to the shaft itself.
Tools Needed:
Jack stands or a lift
Heavy duty power drill with standard sized bits for metal
Hacksaw
4" or so grinder - not necessary with the hacksaw, but nice
Vise or similar clamping device
Brass or dead-blow hammer
Measuring tape
Socket set and wrench
Press
Rags and cleaning aids for the torque tube
Your beverage of choice
Special Tool Needed:
I. Parts
5’ of 5/8” threaded rod. 1 piece is preferable but 2 with a coupler is acceptable.
2 or 3 5/8” nuts with a couple of large flat washers.
3” by ¾” piece of band iron 1/8” thick.
Size 10/32 by 1” bolt and nut
Round piece of flat steel 4 ½” across and at least ¼” thick with a 5/8” hole in the center. This is the hard one but can be made or found without too much trouble. I used a ½” thick piece and cut more holes around the center to be able to see into the tube.
II. Tool Assembly
You will need to cut a 1/8” groove in the end of the threaded rod with a hacksaw approx. 2” deep to house the band iron. I tried it with a 4” grinder but the groove was too wide and left too little threaded rod to be able to bolt through.
You will also need to drill a 7/32” hole through the end of the threaded rod 3/8” from the end. Grinding the threads from the side of the rod will make it much easier to drill.
The piece of band iron needs a 7/32” hole drilled through it in the center
lengthwise and offset toward one of the sides approx. 1/8” (See drawing) Cut
or grind the band iron into the shape in the drawing and bolt it into the groove
cut into the end of the threaded rod. The angle cut on the end will help you in
rotating the band iron to the desired position. Tighten the bolt enough to
provide a little bit of friction against the rotating piece of band iron. You
may need to grind the bolt down to approx. 7/8” to fit through the center of
the bearing.
Tool Illustration
The Procedure:
Once you have the tool assembled, put the torque tube in a vise or similar clamping device with plenty of working room around the front. Remove the shaft by sliding or tapping with a soft heavy hammer (brass or dead-blow). Take note which end is the front and which is the rear. The rear has a groove cut into the splines to accept the rear pinch bolt.
Start with the bearing closest to the front end of the torque tube. Measure the location in relation to the end of the tube. Align the band iron with the threaded rod so it will fit through the bearing. There are three ways to get the tool situated properly. 1. Slide the tool through the center of the bearing and pull slightly back toward yourself to open the end of the puller. It gets much easier after the first one. 2. You can also push it down to the next bearing to help in moving the band iron to the desired position. 3. With the end cut like in the picture, you can also spin the puller and that should rotate the band iron to the desired position. (One end is heavier than the other) Once you have the band iron moved horizontal to the rod, center it in the bearing.
Slide the round metal plate over the threaded rod to the torque tube. Put a washer and nut on after and as you tighten the nut, it will pull the bearing toward the front of the tube. If you run into the coupler or are at the end of the tube, back off the nut and plate and put a couple of deep sockets in between the plate and the tube. This will allow you to pull the rod out far enough to remove the coupler and re-install the plate to continue pulling, or remove the bearing completely.
Measure the next one. Repeat.
If you are lucky, measure again and repeat.
Now you are ready to replace the bearings themselves. In mine there were inserts inside the bearing to fit the shaft. Use a socket (I used a 13/16”) and a press to push them out. Don’t worry about bending the tabs in first; pressing them out will take care of that.
Once the center spacers are removed, remove the bearings from the carriers using the same procedure. (I used a 1 ¼” or 34mm socket) They only go in or out one way, pretty hard to mess it up.
Once everything is disassembled, take a second to clean everything up and check the condition of the carriers. I don’t know if they fail or not but it surprised me to see plastic on the outer edge.
Re-assembly is just the reverse order. Press your new bearings (#6006) into the carriers and then press the inserts into the bearings. I used a slightly larger socket to press the inserts back into the bearings. (7/8” or 15/16”) Be careful, these can be crushed easily. I do not know if they can be obtained or not. Carefully tap the tabs back down to hold the insert in the bearing. Porsche says that there are no parts available for rebuilding the torque tube.
Once the bearing carriers are completed, re-installing them in the tube is easier than removing them. You will want to pull the bearing in the direction that it will not pull the bearing back out of the carrier. Start the bearing in the front of the tube, using a soft hammer if necessary to get it started square. Install the puller in the opposite direction as you did for removal. Just simply pull the bearing carrier back to the original position. Remove the nut and plate from the puller and slide them back out the front. Start the next bearing the same way and pull it into the pre-measured location.
If your bearings have walked around in the tube (It does happen, mine did) locate them equally spaced along the length of the tube. There are two bearings supporting the torque converter at the rear so if you have only two bearings, I would place one near the front and the other about 2/3 back.
Clean and re-install the shaft, remembering which way is front. It slides into the inserts easier when it is clean. Keep a careful eye on the bearing carriers to insure that they do not move in the tube while re-inserting the shaft. The shaft should rotate easily by hand without binding.
Now, you are ready to re-install the torque tube and continue with your life. Pretty simple isn’t it?
While You're In There:
“While you are at its” include the seal around the torque converter and the automatic transmission pump o-ring. I would also replace the torque converter bearings as that is what failed in mine. I just did my torque tube as a “while your at it”. The bearing number for the torque converter is #6008. They are as easier than the tube bearings. You should feel good and be ready to tackle anything now, right?
As far as bearings go, the #6006 is a standard size and can be obtained in several styles and specifications. I am using a sealed bearing instead of a shielded OEM type. I consulted my bearing supplier and told him about my application. He suggested a sealed bearing that runs cooler and is supposed to last longer than the original. The factory piece is a #6006 2Z C3 (or C5) HT51 which equates to a both sides shielded (2Z), clearance spec. (C3) and high temp grease (HT51). Discuss this with your supplier and decide for yourself. Due to the “high” failure rate of the original, anything better is more than welcome. Good Luck!
This page was created under the authorization of the author (David E. Lomas) and is used generically. Your application may vary.
Original documentation adaptation and page creation by Barry Johnson 03/02.
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H,
I am in the middle of this right now. Here is some info. I will get the rest to
you after I get home from work.
TC shaft bearings: 6008-2RS1TN9/C4HGJN (SKF bearing)
My quote through KAMAN was more than buying them through 928 Specialists, so I
ordered them form Jeannie.
TT bearings: 6006 ZZ C5 HT51 (SKF bearing)
This is a major pain in the butt trying to find. They are no longer available
anywhere. The C5 tolerance has not been made in forever. Everyone I talked with
is ordering part number 60062ZJEM. This is a SKF bearing. Best price I found is
through KAMAN for $16.68 each. The entire part number on the bearing is 6006 ZZ
C3 GJN. This is the bearing that will come when ordering p/n 60062ZJEM. The C3
tolerance is tighter and the GJN grease replaces the HT51.
Trans service kit is cheapest through 928 INTL, @ $35.00. It is OEM for the
Mercedes tranny.
AT Main Pump Gasket 126.271.128.0 1X
AT Main Pump Sealing Ring 126.272.095.5 2X
AT Oil Pump Seal-large 016.997.144.8 1X
AT Oil Pump Seal-Small 018.997.044.7 1X
AT Transmission Filter Kit 960.307.901.01 (928 INTL) 1X
AT TC Drain Seal 900.123.033.20 1X
Transaxle Drain Plug Seal 900.123.118.30.OEM 1X
AT Drain Plug Seal 900.123.062.30
__________________
Mike
1988 Porsche 928 S4
1984 Porsche 928 Euro
I think we found some NSK bearings in C4 in NZ when we did Eric (Dragon) s '85
TT last year.
C5 has approx 3x the radial internal clearance of C3.
The larger internal clearance is normally used to allow for differential
temperatures between inner and outer races or bearings pressed onto shafts or
into rigid housings causing distortion of the bearing races.
In the TT in a 928, I don't think either of those circumstances apply -the
bearing inner and outer will sit at roughly the same temp. and the bearing is
not pressed into or onto anything rigid enough to distort it.
So I can't figure out why they used C5 but I'm not a bearing specialist. At
worst using a bearing with a closer radial tolerance could lead to a shorter
bearing life. But beggars can't be choosers - if C3 is all you can get at least
the bearings are new - just need to be changed more often.
__________________
Jon in OZ
Most bearing manufactures have this spec 60062ZJEM bearing and it is pretty easy
to find. FAG, SKF, Timken and on and on.
Cheapest is General at about $10 each.
I have to buy a reasonable quantity to get that price.
Roger
__________________
Roger Tyson
__________________
Drive Train
Torque Tube Rebuild
Smooth like silk; well maybe not silk, but like some smooth powerful thing :).
Finally got my torque tube rebuilt and back in the car. Now this is how the
car is supposed to be!! I can't say that I found rebuilding the tube to be the
most pleasant task I've ever done on the car, but I suppose it wasn't the worst
either. I found MSC MSC to be an easy to use source for the torque tube
bearings, their P/N 45666898 is SKF # 60062ZJEM which seems to be a valid
substitution for the bearings in the tube. The directions for disassembly at
http://home.comcast.net/~gq-beej/928/ttrebuild.htm worked fine for me.
I found that pulling the "harmonic balancer" out was just as easy as pulling one
of the bearings, so I took it out too. Good thing since mine turned out to be
damaged. In fact I wanted to get everything out of the tube so I could clean the
insides better, especially once I thought about how I wanted to "pin" the
bearings and balancers in place. The bearings are supported in the tube by
rubber-edged metal carriers, and the balancer weight is also supported between a
pair of rubber and metal holders. Others have described "pinning" the bearing
carriers in place by drilling through the tube and into the carrier at several
places around the circumference of each carrier, then tapping the holes and
driving in bolts. I'm sure that this will hold the carriers, but I was concerned
about the ability to remove the carriers later with the "burr" from the holes in
the tube holding the carriers even with the bolts removed. I would expect that
this burr would tear up the rubber edge of the carrier(s) upon future removal,
not to mention that various metal shavings would be trapped inside the tube when
the holes are drilled and tapped. Also, the bolts directly into the carrier
would eliminate whatever vibration/noise isolation function the rubber edge may
have provided. Finally direct pinning would eliminate the ability for the
carrier to axially align itself with the drive shaft. What I decided to do was
to drill three evenly spaced holes both forward and aft of each of the carrier
positions and to stop the carriers from traveling in the shaft by putting rivets
in these holes. The rivets project into the interior of the tube and form stops
for the carriers. I left a couple of mm's of extra space between the fore and
aft rings of rivets, to allow a little movement of the carrier. I drilled all of
the holes when the tube was empty, and removed any burrs on the inside of the
tube, and then cleaned it thoroughly. This solution preserves the function (if
any) of the rubber surround, and allows the tube to be disassembled again
cleanly in 20 more years :).
All very good, BUT when I actually got my tube apart I found that the bushing in
the front bearing was worn out, the middle carrier was broken, and one of the
mounts for my balancer was shot. I knew that my front bearing was out of place,
but it turns out this bearing wasn't even contacting the shaft, due to the worn
bushing. The middle carrier had the centre "pocket" that actually retains the
bearing completely broken away from the outer rubber coated ring, so this one
wasn't supporting the shaft either. The forward mount for the balancer had
failed such that it allowed the cylindrical weight part of the balancer to
contact the shaft!!, at least sometimes, based on the marks on the shaft. So, I
really only had the rear bearing operational, and the balancer weight was
dragging on the shaft. What a mess. At this point I was wishing I'd just popped
for a rebuilt unit. But, a rebuilt unit would have had bearings that would
probably just migrate out of place later on me anyway, so I'm happy to have done
it myself after all. So, I needed a bushing, a carrier, and a balancer mount.
One lister offered to make me a bushing (thanks Jerry!!), and another suggested
that a carrier could be machined out of a urethane wheel (excellent idea
Barry!!). This still left me without a balancer solution. I know that some have
left the balancer out, but I read that it was designed to damp a vibration at
4200 rpm and I did have just such a vibration, before my DE spin when my
vibration problems got much worse. It is my theory that the middle carrier
somehow broke during that spin, though I really can't say why. What is for sure
is that my vibration started immediately after the spin, and is now gone once
the tube is fixed up. So, I needed parts. I called around the Toronto area and
found a "good" used tube for C$400 which should either be able to provide parts.
or be a better rebuild candidate than my tube. Kind of pricey, but still less
than a rebuilt and no 2-way shipping. I kept looking. I then called Whaletail in
Kitchener, and Randy there seemed to want to help. After a couple of days he
came up with a somewhat "rough" tube for C$50 (~U$35)!! Now that's more like it.
I zipped out to Kitchener and picked up the tube. It was basically in better
shape than my own tube, and provided all of the parts I needed to complete my
rebuild.
Also, a by the way, I was able to remove the torque tube from my 83 US 5 Speed
without undoing the rear suspension at all. There is enough room to shift the
tranny back and tilt the tube down far enough that it can be removed under the
bell housing.
Eric Buckley
83S 5Spd. Red
Smoooooth!!!