Transmission swap

[Rich in Vancouver]

I have been gradually assembling parts to do the swap on my early TR7.
Everytime the subject comes up I find another part that I may/may not need. I currently have a 4-speed flywheel and a 4-speed backplate.
Will that work with a 5-speed gearbox and clutch? or should I go with the 5-speed flywheel and backplate?

I checked the Rimmer catalog and it shows one flywheel for 4speed and early 5-speed and another for late 5-speed.
I take it that the 5-speed backplate is only needed when the late 5-speed flywheel is used??
(I do have everything I will need from the gearbox back, including driveshaft, rear end etc. and have new oil pump and seals/gaskets in the gearbox)

Thanks,
Rich

1975 TR7 ACL764U

[Mowog73]

Are the speedometer different between the 4 spd and 5 spd, i.e. difference in turns per miles?

Mark

1973 MGBGT, 1976 TR7, 1980 Spitfire 1500

[V8Wedgehead]

The speedometers are the same any typically I have swapped the 4-spped and 5-speed 140 mph speedos and it is all in the tires, rear end ratios and final gear in the transmission that accounts for accuracy. On an other item the TR7s build both very late and TPV onward have a 3.45 rear end. The give away is the double buldge bonnet/hood. If a convertibel has the double bulde it almost 99% of time has the 3.45:1 rear. Single buldge is the revvy 3.90:1 rear. Beside wokring for Woody Cooper at the Wedge Shop for 5 years and my owns armada of cars I have parted out a lot of TR7s to keep TR8s alive.

Michael
1980 TR8 FHC/Works Rally Project

"If it is broken then fix it....if it is not then make it faster!"

[Shauniedawn]

Re the two backplates photographed:

Early TR7 and Dolomite Sprint had backplates that were not countersunk.

Later TR7s had countersunk holes.

Flywheels differed between Sprints and TR7s (5 speed) as the Sprints is lighter.

I have no knowledge of the 4 speed flywheel, and therefore cannot comment.

I am 99.9999% certain that the bellhousing of the LT77 bolts directly onto <b>any </b> TR7 / Dolomite Sprint/ Dolomite 1850 as they all share the same block. However, differeing flywheels may mean that the retaining bolt heads may foul - but this is easiy rectified.

Shaun.[:)]

http://www.flickr.com/photos/12691409@N08/

[terryjm1]

On the subject of overhauling the 5 speed, I have swapped in many 5 speeds and have only had one that needed any significant overhaul work. It made more sense to find another "good" used unit than overhaul that one.

I would just do the easy stuff. Replace the oil pump and rear seal for certain. It is an easy and inexpensive job. Change the front seal as well. From my experience the single most critical failure is the front shaft bearing. When you have the trans out grab the input shaft and see how much play there is. If it flops around you at a minumum need a new front shaft bearing and likely there is much more wrong.

My opinion is that the front bearings fail for three reasons. The oil pump is bad and not enough oil gets to it. The pilot bearing/bushing is bad and causes excess pressure on the bearing. And the oil seal is bad causing fluid loss. So, make sure you replace the pilot bearing/bushing. The pilot bearings are very fragile and susceptabe to damage when removing and repalcing the trans. I recommend replacing the bearing with a bushing as they are much more rugged.

Terry Merrell
St. Louis, MO