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.