View Full Version : TR6 TR6 Transmissions issue

09-04-2006, 09:24 AM
I was crusing around town yesterday and noticed that my transmission is jumping out of 3rd gear. Only happens when in 3rd and decelerating, I guess I can put up with it for a while, any one had a transmission rebuilt? By whom and were you satisified?

Geo Hahn
09-04-2006, 10:57 AM
I assume you're aware of the popular conversion option that puts a (readily available) Toyota 5-speed in your TR with no visible changes (from the cockpit).

If I had a non-OD gearbox and was facing a rebuild I would think long & hard about that conversion.

09-04-2006, 11:01 AM
Quantum Mechanics (John Esposito) is reliable and does quality work. Check out his website and give him a call. He will answer any questions you have. The 5-speed is a popular option. Cheaper to overhaul your tranny. Either way, good choices.


09-04-2006, 11:10 AM
i took the time to rebuild my own 4-speed and added an overdrive unit in the process. this is not rocket science and anyone with simple mechanical skills and the ability to research the job can accomplish.

09-04-2006, 02:51 PM
Hi Hondo,

By any chance, are you using a synthetic oil in the gearbox? If so, that often causes popping out of gear just as you describe. A switch back to standard mineral-based 20W50 racing oil (non-detergent) in a 4 speed box will usually cure the problem. In an OD gearbox, use 30 to 40W racing oil instead.

Even if you are using mineral-based oil already, when is the last time it was changed? I'd try fresh oil in there, before anything else. Might be all that's needed.

If it's not the oil, i.e. you are already using non-synthetic oil and/or fresh oil doesn't help, another common cause is the shifter rails and detents in the top cover of the box. Here it's mostly an adjustment to compensate for wear, or possibly some gradually weakening/softening springs and/or worn detents that need replacement. This is an opportunity perhaps to replace some of the seals up there, if needed.

These adjustments are detailed in the factory service manuals, but I suspect they are more complicated than they appear and I've heard of more than a few do-it-yourselfers who got into problems here. Others were happy with the results. Personally, I've not rebuilt/adjusted a top cover and would send one of mine to one of the experts, rather than mess it up with my own ignorance and lack of experience!

There is a possibility the problem is the result of wear and tear in the box's gears, bushings and such, too, needing more extensive work. But I think this is a bit less likely than the above two causes, which are less costly to correct and are certainly worth checking out first.

John Esposito is "the man" on the East Coast to check out the box and get it back into top shape for you, especially if you want to keep your original gearbox. He and a few others are also capable of uprating the gearbox in some ways, if you are interested in doing so or your car's state of tune demands it. "Uprating" can include replacing brass bushings with steel or needle bearings, increasing the amount of bearing surfaces in some key areas, replacing solid thrust bearings with roller-type, improved hardening on shafts that are prone to wear, etc.

Uprating is largely done for two reasons: 1. To improve the gearbox's durability, expecially with higher output engines that work it harder, by strengthening areas that experience has shown to be weaker and more prone to breaking. And, 2. To reduce drag on HP - some of which is inevitable in any gearbox - which will in turn transmit more of the power the engine is producing to the diff and, ultimately, the rear wheels.

There are also usually rebuilt/exchange g'boxes available through the major vendors like TRF, VB and Moss (Rimmer Bros. or Moss Europe in the UK). Exchange units typically give you fewer choices and are usually only in standard build, with little or no uprating done.

I think TRF does their own rebuilds, at least on the more commonly available gearboxes. I believe they also would rebuild your specific gearbox, if you wanted the orginality and request it (email John Swauger, if you wish).

VB and Moss probably source their gearboxes from rebuilders in England. Getting a rebuilt/exhannge box, you can't be entirely sure you'll get an exact replacement. It might be a "saloon" car gearbox case, with TR6 innards, for example. Should work fine, but there might be some minor cosmetic differences.

Hope this helps and it would be great if this is something relatively simple and inexpensive to fix!


09-04-2006, 06:26 PM
I am not familiar with the insides of a Triumph, but I have had the same problems with old General Motors and Jeeps. In both cases the syncronizers were worn. I changed the syncronizers and things were right with the world. This is not a bad job on the old GM & jeep transmissions. Again, I am not familiar with the TR tranny. Pete

09-05-2006, 06:47 AM
I have the same problem in second gear with my TR3A gearbox. last summer I rebuilt my TR4A gearbox and added an A type overdrive to it. In the process of that rebuild I was looking to see what the problem in my TR3A gearbox might be (since they are in exxence the same box). From that process I am 98% sure that it is the detent/spring/ball issue as described by Alen above. I hope to get to my TR3A gearbox this fall and fix the problem. This will confirm my theory. Let us know if you find the problem. The good news is the detent/spring/ball issue can be repaired without removing the gearbox from the car.

09-05-2006, 11:17 AM
A gearbox that pops out of gear is worn. Take this as an omen of worse things to come. Rebuild it now when you can plan for it, or later after being towed home and for lots more money.

Last year I rebuilt my TR6's gearbox. This transmission would pop out of gear. Ok, I put off the rebuild, then one day it sounded like a cement mixer. It cost me $600 in parts (needed a new counter shaft gear). It would have cost more, but fortunately I had another trany I could scavenge gears and shafts from.

As to rebuilding your own, I recommend it only to those with significantly above average mechanical skills, tools, and the ability to improvise.

09-05-2006, 12:35 PM
thanks for the answers, I did talk to John at Quantamechanics and he said poping out of third came first then poping out of second during acceleration would be next. I could probably rebuild it myself but dont feel to confident and in the end usually will cost me more, so now I face the delima to 1. pull my trans out and send it to John so I can keep the original gear box 2. send mine and upgrade to OD, 3. get his OD transmission and send mine back as the core??????????? or should it be $$$$$$$$$$$

09-05-2006, 01:25 PM
Do I get OD? Ask yourself would you have done this otherwise? Look at how you use the car and does the extra $$ for OD make sense. I have had OD on other cars but have not missed it on the 4's and 6's I have owned.

To swap or rebuild the original box really comes down to a couple things. Can you do without your car while yours is refurbished. If yes, then have yours done.

I forget the specifics, but there were changes to the TR6 series gearboxes that affected low end gear ratios and the constant speed spigot. Having your box rebuilt will greatly reduce the chance that these changes are not inadvetently added or removed from your transmission.

I am sure there are other considerations I am missing.

Good luck

09-05-2006, 01:31 PM
when I rebuild my TR4A box last summer it was not all that hard. The reason I started that project was my countershaft bearings had disintegrated. In the end I rebuilt it then took it apart a second time to mate the A-type overdrive to it (which means I took a second box apart and removed the overdrive then built it back as a non-overdrive). All in all I would not hesitate to take on that job again. It is not rocket science and all it takes is a clean spot to work, a couple of home made 'special tools' and lots and lots of patience (in all it took two full days, split over a week, I think).