TR6 Transmission Tools

by Bob Lang, lang@isis.mit.edu , of New England Triumphs

Several years ago, syndicated columnist Dave Barry wrote an article that fully explained the mystery of the automobile transmission. In short, he explained that nobody really knows where transmissions came from, but that they were probably left here by aliens. He further postulates that automotive engineers felt that transmissions should be incorporated into cars anyway. Of course, this is a gross simplification of Mr. Barry’s epistle, but it does make a good point.

I have always been fascinated by transmissions in several ways. On those occasions when I had to work on a transmission, I started out thinking that there was no way I would ever understand how they worked. This was followed by a smitten of understanding as I dismantled the unit and eventually some real understanding of the process as I reassembled the unit and reinstalled it the car. When I finally actually used the car, I felt I had reached a notable goal. And in every case everything worked just fine.

Well there was a unit on a certain ‘Mericun car in my past that didn’t last too long after the rebuild, but that as they say is another story.

At any rate, after recently rebuilding the TR6’s transmission I realized that I actually learned things in the process that I could share with New England Triumphs readers. Specifically, I learned a small amount about fabricating special tools and I also figured out a few tricks that make the assembly process a whole lot easier than that offered in the Robert Bentley TR6 manual.

The first article is about tools.

A quick look at the Bentley manual indicates a list of several “special” tools used to get everything apart. For instance after taking to top off of the unit, the next step is to remove the “constant pinion” shaft. This step requires one of the dreaded special tools.

Flip to the back of the manual, and pictured there on page 596 are tool numbers S-4235A and S-4235A-2. Now, I have had the Bentley manual for over 10 years, I have looked at that transmission tool just about every time I have thumbed through the book, and I only recently realized exactly what that tool is. It is a slide hammer, aka a dent puller.

Tool number S-4235A-2 is merely a device that clamps onto the constant pinion shaft. I wound up making this tool by taking a piece of pipe that was about an inch and a half inside diameter and about ten to twelve inches long. On one end, I welded a piece of steel across the open end and welded a 1/4 X 20 nut in the middle of that. At the other end, I put a couple of 1/4 X 20 bolts that are attached perpendicular to the pipe. These bolts clamp against the constant pinion shaft. Note: the splines on the constant pinion shaft are symmetrical, so you may want to put three bolts instead of two. This will eliminate the possibility of making the tool slide up the shaft too easily. The slide hammer attaches to this “tool” and you basically “yank” the constant pinion shaft and bearing out. This is a pretty simple tool.

Armed with this valuable knowledge, I set off to determine what the next special tool needed was.

The manual indicates that you need a pretty elaborate tool to remove the center transmission bearing. I found this to be not true. It would be easier with a special tool, but you don’t absolutely need one. Warning: if the center bearing is tough to get off, your transmission should be reassembled and worked on by skilled professionals.

My experience was that the center bearing was relatively easy to take out with a very small amount of heat and some big-ish hammers and some soft drift material like some scrap aluminum or brass.

You don’t need any special tools to remove the countershaft, you just need to be really careful that the countershaft thrust washers do not fall into the case. More on that later. I did use a 1/4″ wood dowel to push the countershaft out, so presumably you can list that as a “special” tool.

Pulling the mainshaft gear cluster apart is a little intimidating. The manual indicates that you can use pliers to remove the big circlip that holds gears three and two in place. I found that a pair of very heavy duty piston ring pliers could be used to the job, but the process stresses the circlip so much that it is rendered unusable anyway.

Thus, the next tool of choice is a good old Dremel moto-tool. Armed with a 426 fiber-reinforced cutting disk and low speed on the Dremel tool, carefully cut the circlip at a point that is directly opposite from the opening on the circlip. Don’t miss! Don’t nick the mainshaft! As you cut some meat from the circlip, it will get very easy to open up with the heavy duty piston ring pliers.

Of course when you reassemble the unit, you will need to install a new circlip. The manual shows tool S-176 for this job. Note: the back of the manual indicates this tools is called tool number S-167A, I wonder which one it really is? I found that you can use the heavy duty piston ring pliers to get the circlip started onto the splined section of the mainshaft, but instead of tool S-176, I discovered that you can use a spent top-hat bushing (second gear) from the TR transmission to act as a tool to push the circlip into place. Just tap on it with a hammer until the circlip seats. So don’t toss those old top-hat bushings! Also note that the early top-hat bushing is bronze, and the flange is bigger, so the early bushing is better to use for this purpose because it will fit early and late shafts and it also has a bigger “hitting” surface than the later steel top-hat bushing.

A set of gear pullers is required to pull the constant pinion bearing from the shaft. The only special consideration for this tool is that you need to obtain or fabricate some jaws for the puller that can fit into the groove normally used by the locating circlip. I borrowed a set of gear/bearing pullers from a friend, there was a set of jaws in the kit that fit well enough to get the job done.

If you do a transmission job, you will need a good set of feeler gauges. You will also need a set of vernier calipers or a micrometer to measure things. If you don’t have the calipers, borrow a set before you do the job. You do not want to guess about the tolerances if you want a reliable gearbox. There really is not too much measuring, but those readings that you take are very important. The last “tool” that I’ll mention for purposes of doing this type of job is bearing grease. There are several points in the assembly of the transmission where you need to hold parts in place while you fit other parts together. This is complicated by the fact that if you do not succeed in holding the parts together, chances are you will have a part fall into the transmission case where you cannot reach it easily and you will have to totally dismantle the transmission to rectify the goof-up. I know, I wound up tearing mine down at least three times during my reassembly because either the thrust washers for the countershaft slid down or some other inane thing. Get some really thick wheel bearing grease for these tasks, the more “tenacious” the better. Clean the surface that you want the part to stick to with a rag and then apply the grease only to the side of the part that you want to “stick”. This comes in really handy.

So, as you may have surmised, the “special tools” needed for a transmission job on a TR6 are not that unusual. I did have to fabricate one tool to do the job, but that one was pretty simple. If you don’t know how to weld, enlist the help of a friend.