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mg_zt_t
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Discussion Starter · #1 ·
What's the difference between the TorSen differential and the conventional planetary gear ones? Here's a couple of pictures showing the differences:

See pictures here:

http://triple-m.co.uk/phpBB/viewtopic.php?t=1599

In both pictures the TorSen differential is on the left. Note the diffrence in the speedometer drive. It's the white-yellowish nylon worm drive on the TorSen and the darker metal one on the conventional unit on the right.

Well, been working on my TomCat Turbo's gearbox recently and this weekend, stripped a similar PG1 which came off my B-reg (1985) Montego Turbo about five years ago. My 1993 TomCat is currently running around quite happily on another Montego Turbo PG1 Gearbox except that with the Montego Speedometer drive assembly, it's reading far too fast.

To overcome the speedometer drive problem, I'm currently considering using the TorSen Differential assembly in the conventional PG1 Box. This will solve the speedo drive problem. However, I believe the differential sprocket and its partner on the countershaft are a machined match. However, as the Montego Box has a similar mileage and wear to the Tomcat's item, I've 'dry run' assembled the Montego Turbo gearbox using the TomCat's TorSen Differential. The result appears OK.

I did notice that there is perceptible play in the TorSen's plastic caged differential bearings. Could not detect any play at all in the steel caged Montego Turbo equivalents. So, using my trusty three legged puller ( Oh Matron ...:lol:) I removed the steel caged races from the now redundant Montego Differential and slotted them onto the TorSen Dif having removed its plastic caged items. Spun the bearings and they felt much better.

Dry run assembly appears successful. Placing a stout bar into the gear change input shaft, I was able to select and check the operation of all six gears.

Tomorrow, I will disassemble the gearbox again, thoroughly clean it and use sealant on the casing faces. Then final assembly.

I will take the chance that this selectively part-worn 'hybrid' gearbox will be OK on the car. When time allows, I'll remove the current Montego gearbox and fit this 'hybrid' one. If it does not work out successfully, I will only have spent time and very little money on the project so far. One thing's for certain - I sure do understand the PG1 box now and its various foibles ...That at least is a bonus.

Would appreciate any comments on this concept, particularly from those with more experience of such things than I, or who may have 'been there., done that' or something similar.

I will x-post this over on the Rovertech.net Transmission forum too in the hope of reaching a wider audience.
 

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mg_zt_t
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Discussion Starter · #4 ·
Vincero said:
Just for anyone wondering what/how a Torsen system works:

http://www.answerbag.com/a_view.php/1770

Sounds like black magic to me.
Thanks for that useful link. One line sums it all up for me:

"With an open differential, a car will deliver power to the wheel that has the easiest time of it - this means the wheel with the least grip"

That in a nutshell has always been the failing of a conventional differential as anyone trying to drive their conventional differential car in a muddy field will discover - remember the 'early' season British Grand Prix at Silverstone a few years back...:( Mother nature will always have her final say ...:)

Having looked closely at the TorSen I removed from my Tomcat and examined its operation, not so much 'black magic' as a marvel of engineering. Obviously far more expensive to produce than the conventional planetary gear differentials as a glance at my pictures will clearly indicate.

Anyone know who thought up and designed the TorSen .... it's a miniture engineering marvel.... or was it simply a progressive development of similar limited slip jobbies.
 

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Is this a like for like replacement?

One might be nice for my ZS180, but not for a couple of years I guess, it'd have to be out of warranty :) Would it fit?
 
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