photos and story by Derek McCallister
The torque tube on the 924/944/928 is nearly identical on all of them; the difference is of course bearing diameters, insert diameters, and torque tube diameters but the idea is all the same. You might hear horror stories about their rebuild, but they’re quite simple to do, as a matter of fact. The first thing to decide is if you just need to do the torque tube, and if you need to do the clutch as well. I did my torque tube while it was out of my 944 and did the clutch. However, it’s not that much work to drop the transmission and pull out the torque tube to just rebuild it.
Let’s start with what you will need:
- 6FT piece of All Thread. It does not necessarily need to be an acme thread, but it should be of good quality. You WILL be putting a lot of force on them.
- 5 nuts which will fit your all-thread
- Really good wheel bearing grease or preferred lubricant. This will be necessary when putting force on the All Thread, otherwise you can expect ruining your all-threads. Ask me how I know.
- 2 heavy duty washers that also will match the All Thread
- 6ft of ½” pipe. Inner diameter must be thin enough to fit OVER the nose of the torque tube shaft so that you do not harm the insert for the pilot bearing.
- 3” diameter washer. Yeah, really.
- Dishwater soap
- Tape measure
- Huge hammer
- Safety Glasses
- A heavy pulley, boards, or something you’ll be able to use as leverage to pull and push bearings out of the tube.
Step 1 - Measure the length of your torque tube. You will want to make sure that your All Thread is just a little bit longer than the torque tube. Ultimately it needs to span the length. So far, the torque tubes I’ve worked with are pretty close to the All Thread length, somewhere around 6ft, maybe a hair less. Set a nice large area aside. Torque tubes are heavy, huge, and long. This is not something you can just put on your work bench to rebuild, unless of course you have a really badass work bench. In which case, if you do, I’m envious.
Step 2 - Measure the depth of your bearings the best you can. Also measure each tip of the torque tube shaft to see how far it protrudes. Once you put the shaft back in, it needs to protrude the same amount, otherwise it may not insert into the pilot bearing properly. This is going to be a critical step to ensure it goes together the same way it came apart. Upon reinstalling the bearings, they should be in roughly the same places. Measure in with your tape measure and make a mark against where you start at the tube. For instance, if bearing 1 is 8 inches into the torque tube, mark that on a piece of paper as “bearing 1”. Measure the rest of the bearings and how far in they are and you should have various measurements for each as they go further down the torque tube. We will come back to this part later.
Step 3 - We need to hammer out the shaft. At this point, it’s probably a good idea to put on safety glasses since metal can chip off from the pipe and the last thing you want is a piece of metal in your eye. I recommend doing this starting from the Pilot insert end. Using your ½” pipe, insert it over the end of the pilot insert. Then, using a huge hammer, starting hitting the end of the ½” pipe to drive the shaft out of the bearing inserts. The steel pipe is far softer than the shaft, so it should not dent it or ruin it. You may notice that the end of the pipe will mushroom. This is okay. Take your time since this is not an easy task and it can take a while. The initial friction with all the bearings is the toughest. However, as the shaft leaves each insert, it gets easier and easier.
Step 4 - Make some soapy water and get ready to push those puppies out! What we will begin with doing is essentially using the plates/boards as braces, and then bracing it up against the torque tube. On the other end, the 3” washer will be held in place by 2 nuts. The idea is to double nut them tightly together, thus making it so the nut cannot back off. One could weld them, but this may be a bad idea if you make a mistake and need to back them off.
Using your soapy water, be generous and do what you can to get the water in the coating of the torque tube. You’ll want water lining the walls. Shake it around if you can, spin it, do whatever you can, get the inside as wet as you can. Using the above diagram, you will want the plate and nut on one side of the torque tube, with the 3” washer at the other side.
Step 5 - With a now wet torque tube, you will want to use the bracing technique at the top of the torque tube. Lubricate the All Thread with wheel bearing grease BEFORE putting it in. Then, using the nut against the large pulley or whatever you’ve chosen to brace and use as your “pulling” machine, hold the nut still against the pulley with a wrench. Then, using a double nut at the tip of the All Thread, turn the All Thread counter-clockwise. Basically, pretend that you’re taking out an infinitely long bolt. One way to speed this process up is instead of using a large torque wrench such as I did, use a power drill with a socket at the end if you can.
Here is an example of the All Thread very far out. A good example of what it should look like.
Once the inserts are out, you will note they look like donuts. It is crucial that you not bend these, they are incredibly hard to get. You will need to measure and have new sleeves made unless your inserts are still in good shape and can be re-used (which is very rare).
Step 6 - Press out the old bearings out of the donuts. Replace them with FAG 6006 2Z bearings. These are pretty standard bearings and can be had around $100-200. Then insert the inserts back into the torque tube. A good test is to try and slide one of these donuts with the inserts and new bearings over the shaft BEFORE installing them. If the sleeves feel loose and it easily floats over the shaft, you need new sleeves. If they are tight then they can potentially be re-used. The idea is that the sleeve should be firm enough that spinning the shaft spins the bearing without spinning itself. Think about the amount of force you needed to drive the shaft out, now compare in your mind how much pressure is on the sleeve. If it feels too loose now, toss them and have new sleeves made. There are dimensions available on clarks-garage.com where you can have some made out of Delrin. I had some made out of the same material they use for plastic pulleys which have the same hardness as Delrin, but waterproof. It cost me a total of around $60-80 to have the machined since the setup was difficult for the machinist.
Step 7 - With the bearings and sleeves now pressed in, we can begin the process of putting them back into the torque tube. Now, before we do this, make sure the torque tube is nice and dry. We do not want to leave our rebuild with a wet torque tube. Even though the bearings are sealed, that moisture is going to be trapped in there if we leave it—so dry it out. The idea of the soapy water was to easily get them out. We’re putting them in one at a time, so it is not necessary to have lubrication.
Reversing the process is easy. One bearing at a time, we are going to use the 3” washer and same method; except we are going to do it one at a time. Starting with the bearing closest to the front, insert it and use the all-thread to pull it up to the measured point for bearing 1. Then do bearing #2, bearing #3, and then finally the last one. This may take you a while because you need to be very careful about measuring them as you do it, not to mention, you’re basically repeating the same process 4 times. As each bearing is pushed up the torque tube, you can measure from the opposite end and measure how far it takes before your tape measure hits the 3” washer and then if it’s deep enough, you know the bearing is in place. Ensure that they are going down the torque tube STRAIGHT.
Step 8 - Hammer the shaft back into the torque tube. Although it is recommended first to check all of your inserts, make sure they are straight in the tube, ensure they are lined up and measured to the same lengths. Once you’ve done this, use the same method you used to drive it out, to drive it back in. This time you’ll notice it will get harder as it makes it into each insert. Be very careful with the first 2 inserts since it is possible to have the shaft at a slight angle and accidentally damage the inserts of bearing #2. Take extra care with that one. Keep hammering until you feel you are “Close” to where the protruded point of the shaft was. Then measure with a tape measure and use a soft mallet to drive it to the measured point.
It is worth noting that it is actually easier to drive the transmission shaft too far in than it is to have the shaft driven too far out towards the pilot end. The reason for this is that if you go to install the torque tube and find that the pilot end is driven too far forward, you have to remove it, hammer it back, reinstall, and try again. If, however, it is not close enough to the pilot bearing upon installation you can hammer it forward with the tube in place and not have to remove the tube again.
If you’ve done this then congrats, you’ve rebuilt your torque tube! That wasn’t so hard was it? Although if you used a torque-wrench like I did, you’ve probably got one super beefy arm by now.