GT6 Transmission - Part 2 - Making a testing Rig 

Several years ago I decided to rebuild my gearbox and J-Type overdrive. In researching before I started the job I ran across the Buckeyetriumphs.org website. They have a wonderful set of technical articles on a lot of the issues revolving around our Triumphs. If you go to the gearbox section of the articles it also includes detailed instructions on rebuilding the overdrive, both the A and the J. It also includes a section on building a test bed for your overdrive unit that can also be used to test the gearbox. My memory is that he suggested a 5 hp electric motor to turn the overdrive and I had several motors that I tried. I started with a 1 HP unit then moved to a 3 hp unit and it was not until I decide to remove my 5 hp compressor motor and put it on the rig that I was successful in getting it to turn. Mark Wilson

Elin, I also have a GR number in my GT6 Mk 3 and I looked on forums and apparently it designates that it was a Gearbox Rebuilt (GR).

Good to see a discussion about transmissions. Your test rig should serve you well. I almost feel obligated to say something about the bottle jack, but I won't. Thanks for the update, Elin!

At the price of wood!! Nowadays Gold would be a cheaper material for your Test Stand!! 😉 You could make a steel rolling cart and mount any transmission with some adaptor brackets and motor can be lower in cart too ( adjustable for different lengths transmissions etc... Also a transmission holder for repairs if you make it universal...swivel transmission like a engine stand does??

Very clever rig you put together there Elin. I think you have the solution in front of you at the end. At least you know they are genuine GT6 parts and you confirmed what the problem is. Not sure I would worry too much about overstamped numbers as gearboxes / engines / axles used as service exchange units had unique numbers regardless of what they came out of and were all stripped down to bare parts cleaned, painted and re used with new bearings etc. So that casing may have come from a GT6 and had a Herald set of gears put in at the service exchange plant.

wouldnt worry too much about the stamp...I gutted a non OD 3 rail spit box to freshen up an OD 3 rail GT6 box and the syncros bearings etc were the same. different ratios and gaskets.

great idea.. a hinged shaft with a second order tension spring( or several) and a tensioner pulley/ random wheel and high-speed bearing.. could it maybe be run off the front with the spline from a clutch friction plate assembly

Having the correct gear ratios and diff ratio is particularly important with a six cylinder engine. Also check the circlips and spacers on the mainshaft.

Excellent video. Love the rig

Good video (as usual). Seems to me that the rig as you have it will expose a common problem in gearboxes - slipping out of gear in overrun and that problem is coming from the worn synchro hubs. Happen's most commonly in second gear in my limited experience.

Buying another used part is a coin toss..it usually ends badly ...best to rebuild and fix what you got... A used transmission might give you " some " parts..or " None useable to you " ...plus they may be hard to find or cost too much..etc.... Rebuild is my opinion Carry on Wayward Son

Elin - The little hole in the transmission casing is an oil drain hole for when the crank main seal leaks (notice I did not say if it leaks).

Count the teeth and measure the diameter of the gears, the gears are in sets. The set is the main shaft gear and the lay shaft gear has to belong together. Early Porsches have removable lay and main gears so you can switch and swap depending on the race track you’re running at.

Thx for the video great one

Elin, another interesting video showing your resourcefulness, but please add a No Volt Release Switch in an easy accessible place. I am sure that you take great care, but relying on yanking out the cord is not the answer if something were to get caught in that whirring set of gears or drive belt

Good set up.

[5:21] That bottle jack looks more precarious than it probably is.. still, makes me nervous :)

For the first time I am actually starting to understand the voodoo that is a transmission.

First....great vid looking into the transmission

Elin your red bottle jack is going to fall off the shelf and hit one of your kids .