Triumph Repair: TR7 4 speed pops out of 3rd gear, ford differential, cv joints

Question
Howard,

  I have an older 1976 TR7 with a 4 speed.  It pops out of 3rd gear as soon as I let off on the gas.  The rest of the gears are fine and shift well.  Do you know what the problem might be ?  Also, there is a TR7 5 speed for sale in my area, if I opt to upgrade, is it a bolt on switch or would I need a different drive shaft or more parts ?

 Thanks,

 Steve.

Answer
Hi Steve,
It could be several possible causes from something as simple as the shift lever fouling on the tunnel and soft motor mounts allowing the engine and trans to move too much. Or it can be the mainshaft spacing is wrong because the rear nut is loose or a worn spacer between gears. Other causes are worn or bent shift fork or the sliding splines that connect that gear to the hub can be worn in a bevel shape and the reverse load on decell causes it to walk out of gear.

The 5 speed box is a far better design than the 4 speed box and as I remember they will exchange but I so think the drive shafts are different but I don't remember if the bolt patterns were different. I think the 5 speed shaft had CV joints on both ends. The differentials were different too. The advantage of the 5 speed box would make it worth it even if you had to have a driveshaft shop make a drive shaft for you. The flange pattern must be a common pattern because I just had a driveshaft shop make one for me mating a 5 speed TR-7 box to a 8.8 Ford differential and they supplied the yokes. You would have to go to Spicer type "U" joints but you will never notice it.
Howard