Back before Christmas I changed the gearbox on my car. The reason? Well the diff bearings were on the way out and 2nd gear had developed a nasty rattle.

Well for the last few months I've been successfully driving on that box with no mechanical problems. BUT, the speedo is reading incorrectly and after some reading about I've found that the box I have on there was infact from an 800 so the ratios are incorrect (very tall 5th gear) and the speedo drive has 26 teeth not the 23 that the coupe has :(

I have now decided to rebuild my original box and improve it by adding a Type B Torsen limited slip differential out of a 620Ti/Vitty : Before I could start I had to source the LSD courtesy of Lou, and I also acquired another nasp box from Traser for spares if any were needed for my box.

On the left if the spare nasp box, on the right the torsen box.

First task was to strip my original box and clean all the grease and oil off it

And after a couple of hours with the Gunk degreaser... Yes that IS the same box!



And here are the internals of the original box


For those that are interested here is the torsen type B (on left) removed from the vitty turbo box next to my original open diff (standard on the nasp) to show the differences



I then had to dismantle the torsen diff to make it compatible with my car, that entailed removing the original 26 tooth speedo gear (the small yellowy gear under the bearing) to replace it with a 23 tooth gear to get the speedo ratio correct. Next I would need to swap the crown wheels over (the big gear) to keep the final drive ratio correct, however as luck would have it both crown wheels were the same saving me some agro! Then the 6208 uprated steel cage bearings (sourced from P. S. Bearings once again) were fitted.


The reassembly could then commence. Here the drive and main shaft diff housing bearings installed along with the selector arm

And the new torsen diff in place


And thats it so far. I shall now need to strip the spare nasp box to get the drive shaft from it because the cause of my second gear rattle has been found to be my second gear tolerances being outside service limits and showing the early signs of seizing.

TO BE CONTINUED.....

Hi Tom,

Good thread to read, just wondered if the continued was here yet. 8)

Things have been a bit hectic of late, but last night I cracked on with it again and got the countershaft bearing swapped over and test fitted everything to check diff and mainshaft thrust and ordered some shims etc from Rover today to get it all back within tolerances.

So all being well the parts will arrive at my local dealer for me to get it all finished and painted plenty of photos to follow over the weekend if all goes to plan. And after that I can take care of your request ;)

Well middle of last week I finally got the time to get back to work on the box again. I started by measuring all the clearances of the box with the feeler guage.



I then measure the main shaft end thrust


Having measured everything up I had to order a snap ring for the new diff and some new shims to get the main shaft end thrust back within tolerances. So this morning the parts in question arrived at the dealer

Looking at the logo on the stickers I think those have been sat on the shelf for some time!

Heres the shim (the ring with the 1/0.5 marking) for the main shaft in place in the gearbox housing


All the components back in their rightful place in the diff housing and the Hylomar Blue sealant applied reading for the gearbox case to be bolted down.


And then after that I gave the box a coat of etch primer


All that remains is to paint it with the top coat and reattach the clutch arm and breather pipe tomorrow and then I can fit it :twisted:

Remember to apply lots of sticky grease to the clutch arm shaft where is passes through the casing as they are prone to seizing. I always use copper grease but anything that won't budge will be fine.

Lots of work there Tom, looking good!

Hey Tom where do you get all your tolerance/end float/torque values from? I had to farm out the work required on my Ebay acquired 'box because I couldn't find any! I have my original 'box in my driveway and I'm considering pulling it apart to rebuild as a spare unit or for resale. Any help on this wold be great.

Very good pics BTW. You seem to be a perfectionist like me. My mates would happily throw in an oily 'box rather than clean it up, where as I hate putting things back on a car unless they're cleaned up.

Check the PG1 rebuild manual for tolerances and end float values etc. There are pdf copies of it floating about on the net. If you can't find a copy gimme a shout and I'll email you a copy of my pdf.

I've been a little busy of late and only this week finially finished the rebuild with two coats of hammerite hammered finish silver grey paint to go on top of the red etc primer seen in the last few sets of photos.

I've also fitted both diff seals, the oil breather pipe and the reverse light switch. All that remains is to fit a couple of mounting brakcets and the clutch release arm which I'll do when the box is fitted.

Heres the end result, better than when it left the factory!

Do us one