Fitting a TR6 gearbox to a TR3A with J Overdrive

[Royzeboyze]

:rolleyes:Hi all,

I now have a 2.5 gearbox and J Type overdrive rebuilt to something like TR6 spec, this is because the gearbox rebuilder had the necessary new parts. The input shaft has been changed to ten spline inch and a quarter. Will this fit into the 3A flywheel/crank as it is shorter than the original, it is level with the gearbox casing? I am told about 3 eighths of an inch shorter. I was told that the later gearboxes were all shorter so that they could be stored easier, on their bellhousings, without the shaft protruding and causing problems. The nosepiece shaft is two inches and three eighths long. In the Moss catalogue it says to shorten to two inches. I want to install a diaphragm clutch. I know that the flywheel has to be redrilled to fit the new clutch. probably have it lightened at the same time. Will the spigot bush fit? I have a new rear gearbox rear mounting. I need to have the rear flange redrilled. New longer studs and bolts for the gearbox.

The next thing is the speedo drive in the overdrive, I need an angle drive. I also have two speedo drives one with 17 teeth and the other with 20, can I use one of these? They both seem to go into the drive on the overdrive, the cogs seem to mesh OK, but one has a longer shaft than the other. The speedo cable might not go right into the longer one.

Hopefully I can get on soon! ! !

Thanks again.

Roy

[Menno van Rij]

Angle drive is MGB!

 

Menno

[Dave Herrod]

Roy,

I had hoped that someone with more recent experience than me would respond in detail. It is now some years since I went through this exercise and I have forgotton much of teh detail.

 

As the re-builder has changed the input shaft, I assume that the gearbox and overdrive were originally from a saloon or other non-TR application. If that is the case, it is likely that speedo drive gear (can't remember the correct term) within the overdrive which meshes with the plastic gear on the speedo output drive will not have the correct number of "starts" which, at best will result in an incorrect speedo reading and may chew up the plastic gear wheel.

 

I seem to recall that the TR needs a 5 start drive whereas the saloons had eight. (this is where my recollection is a bit hazy) Overdrive Repair Servicers in Sheffield will be able to give you chapter and verse on what is required. From the serial number, they will also be able to tell you exactly which overdrive you have. It was a relatively easy exercise to change the speedo drive gear, but it does involve splitting the overdrive.

 

I also recall that the TR overdives have a stronger spring than the saloon models. In the end, because the friction material weas damaged, I had my O/D reconditioned and upgraded to full TR spec by ORS. They did a fantastic job.

 

Dave

[Royzeboyze]

Roy,

I had hoped that someone with more recent experience than me would respond in detail. It is now some years since I went through this exercise and I have forgotton much of teh detail.

 

As the re-builder has changed the input shaft, I assume that the gearbox and overdrive were originally from a saloon or other non-TR application. If that is the case, it is likely that speedo drive gear (can't remember the correct term) within the overdrive which meshes with the plastic gear on the speedo output drive will not have the correct number of "starts" which, at best will result in an incorrect speedo reading and may chew up the plastic gear wheel.

 

I seem to recall that the TR needs a 5 start drive whereas the saloons had eight. (this is where my recollection is a bit hazy) Overdrive Repair Servicers in Sheffield will be able to give you chapter and verse on what is required. From the serial number, they will also be able to tell you exactly which overdrive you have. It was a relatively easy exercise to change the speedo drive gear, but it does involve splitting the overdrive.

 

I also recall that the TR overdives have a stronger spring than the saloon models. In the end, because the friction material weas damaged, I had my O/D reconditioned and upgraded to full TR spec by ORS. They did a fantastic job.

 

Dave

[Royzeboyze]

Thanks for your help Dave

 

I still haven't had advice as to whether the TR6 input shaft will fit the 3A as it is shorter.

 

Roy

Edited September 22, 2009 by Royzeboyze