tr5 Diff

[peter moffatt]

Hello All,

 

I am currently restoring a TR 250, !! yes another one !! & have a query. This diff I suspect is a TR4A because the rear mounting bracket is bolted on the diff casing with 4 studs. Previous cars that I have done have the mounting bracket inbuilt with the casing. I have counted the 36 teeth on the crown wheel but I can't count the teeth on the pinion because I can;t get access.

My question is are the same ratio diffs fitted to both the 4A & the 250.

 

Cheers

 

Peter

[Lebro]

Surely you can determin the ratio by counting how many turns of the input flange are required to move the wheels 1 turn.

Or better 10 turns, then divide by 10 for the ratio.

Or if only 1 wheel is turning, then count 20 turns & divide answer by 10.

 

Bob.

[GUY BENNETT]

Just had to have my diff rebuilt earlier this year. The PI cars ran a 3:45 diff whilst the earlier Tr's ran a 3:7 diff. I am now running a 3:7 diff, ideal for our twisty roads.

[peejay4A]

Peter,

The 4A IRS diff casing does indeed have the rear bracket stud mounted. Ratios of 3.7 or 4.1 to 1 were available.

The Moss catalogue lists available ratios for the TR5/250 on page 121. It implies that the TR5 ratio was 3.45 and the TR250 was 3.7. Other ratios available (as the Moss cat says) from the competition department.

Edited September 5, 2015 by peejay4A

[graeme]

The rear diff bracket on a TR250 should be bolted on to the diff casing as per TR4A but has the later mountings of the TR6.

 

TR250 standard diff ratio should be 3.7:1.

 

Cheers

Graeme

[peejay4A]

So if it's a 3.7 you're good to go.

[Alec Pringle]

For the record, both my early and late TR250 parts books show 3.7 as the only fitment, there is no alternative either in diff assemblies or crown wheel and pinion sets.

 

In contrast, early and late TR5 books list 3.45 as standard, with the optional crown wheel and pinion sets (not diff assemblies) for competition purposes of 3.7, 4.1, 4.3, 4.55, 4.875.

 

These lower ratios 4.3 onwards, were not sourced from the competition department, incidentally, they were production items in regular use for other applications, and had been for many years - eg the lower final drives for estate and commercial Vanguards, 2000, Standard Atlas and Atlas Major, Leyland 15, 20 and 2-tonner. There was at least one and I think two even lower ratios, as in five point whatever. 3.7 and 4.1 were normal saloon fitments, as in Triumph 2000.

 

Cheers

 

Alec

[peter moffatt]

Thanks for all your input. I now have established that I have 3.7 diff. Where would I be without the feed back from our members.

 

Once again very much appreciated.

 

Cheers

 

Peter