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Triumph Repair/Setting -up and shimming of a 1300cc 1973 spitfire Mk IV


QUESTION: I am in the process of rebuilding the subject differential, can you please help with any information and shimming specks.

Thanks in advance

ANSWER: Hi Albert,

It has 15 to 18 inch lbs for the pinion torque (with no seal)(0.17 to 0.21 kgf.m)(90 ft lb torque on the nut. 12.4 kgf.m)

Backlash for ring gear to pinion gear is .005 inch or 0.13 mm.

Triumph has an elaborate method of setting preload of the carrier bearings but I just set (0) side to side clearance then use a case spreader and add from .001 to .002 inch shims to add a preload to the carrier bearings. Then I check back lash and if it is too tight I just move a shim or two from one side to the other on the carrier bearings to get my .005 inch back lash.

Even though I worked in several Triumph dealerships we never had the special tools to set pinion dept in the case so I just checked the pattern on the ring gear using white grease to see that the pattern was well centered on the ring gear teeth. (If you are replacing the pinion bearings be sure to point the small end of the spacer between the bearings toward the front.)

When the end result was that I had a one to two thousandth preload on the carrier bearings and a 15 to 18 inch lb. torque on the pinion (without the seal) and a .005 inch back lash and the white grease showed a centered pattern I just put the seal in and buttoned it up.

You can torque and loosen the pinion nut because the spacer between the bearings is a solid spacer with shims and not a crush sleeve type of spacer.


---------- FOLLOW-UP ----------

QUESTION: Hi Howard,

thanks for the info, it is perfect, I do however have another question.
I do not have a case spreader, is there another way to satisfy this check?


Most of the shops I worked in had them but I didn't have one of my own and they were a little expensive for how many times I needed one at home so I just made one. It is not hard if you have a little shop equipment. I made mine out of scrap metal I had laying around except I had to purchase a piece of 1/2 inch threaded rod.

Look at one on the Internet to see what they look like and you can see it is easy to make one.
Another option is to look on E-Bay for a used one. Even if you need to modify it a little to use on a Triumph. Often the ones we had in the shops were for other cars so we had to alter them just a little as we worked on a lot of different brand cars. The ones you buy from a tool man will work for most cars.

You just need to put a strain on the differential case so you can slide in the center chunk with the bearing and then release the strain to get a fit check (side to side) with a dial indicator then adjust the shims to take out the free play side to side then I spread the case and add a one to two thousandths shim for the preload. Some cars require more but I don't like much more then .002" preload on most small cars.


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Howard M. Fitzcharles III


Triumph TR-4 up & Spitfire, and Engine theory


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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