wanted 3.9 crown wheel an pinion

[roy53]

As title 3.9 to 1 required

Roy

[BlueTR3A-5EKT]

41 minutes ago, roy53 said:

As title 3.9 to 1 required

Roy

Last one I had went to Tony Lindsey Dean.   Kingston Sports Cars.   I have no idea if he used it or not.

 

 It was a new Leyland Special tuning set for Dolomite Sprint, which is also TR.

3.89:1 Crown Wheel & Pinion.      STR 0578

Edited November 21, 2024 by BlueTR3A-5EKT

[had17462]

Would that be from a tr250 

Nick

[BlueTR3A-5EKT]

No. It’s an unique ratio that Leyland Special Tuning produced and homologised for Dolomite Sprint

[had17462]

Thx Pete learning everyday 

Nick

[BlueTR3A-5EKT]

5 hours ago, had17462 said:

Thx Pete learning everyday 

Nick

Sweeping statement on axle ratios   Apologies if it does not reflect your car’s fitment   

As built new.

All carburettor model cars TR2-3-3A- 3B-4-4A-250-6 had a 3.7 axle ratio  (a special order of 4.1 was available for overdrive fitted cars) 

All PI cars TR5-6 had 3.45 axle ratio

 

Triumph listed ratios.  3.45, 3.7, 3.89, 4.1, 4.3, 4.5 & 4.875.
 3.89 as stated above was Dolomite Sprint Special Tuning  

I have never seen nor sold the last ratio.  4.875.   It apparently came in a commercial vehicle axle.

 

See the effects here

http://www.mintylamb.co.uk/gearspeed/

 

Acknowledgment to Minty Lamb

 

Edited November 22, 2024 by BlueTR3A-5EKT

[Dave McDonald]

On 11/21/2024 at 3:48 PM, roy53 said:

As title 3.9 to 1 required

Roy

Hi Toy, is that cos you’re going to Dpa next year?

I have one for my car (not for sale) and it does make a difference at the end of the Kemmel Straight, also at Silverstone and Snetterton. 
 

Good luck with your search. Could be worth asking Pete & Tom Cox. 
Dave McD

[roy53]

That's the reason . Was feathering at 8000 and praying with fingers crossed at Snett but more so at Silverstone GP circuit. Don't tell John D

SPA ?  still worried about all the red tape. 

just dropped the diff and found the front bracket just hanging by a minimum amount metal. Don't think it would have last more than a few minutes .

Has anyone strengthend these by welding an angle bar across the top front ?

.

Hope all is going well with you 

Roy

[roy53]

Did email them Dave and awaiting a reply.

Roy

[MichaelH]

I had a 4.875: 1 LSD diff in the FIA 4 but ran an overdrive with at straight cut dog box. Gave a good 5 speed box as I only used the o/d in top

MichaelH

[DaveR]

The standard 3.89 is the light duty axle used on the small chassis cars. e.g. GT6, Vitesse 2 Litre, Spitfire Mk4, Dolomite 1500. Ok for normal road use in those cars, but not competition. The standard 3.9 is a  heaver duty axle and was used on the 5 speed TR7.

The standard 4.875 axle was used in Herald 948 Saloon and Standard Eight. Again light duty.

Other rations were-

The standard 4.55 axle was used in the Herald 948 Convertible/Coupe and Standard 10. Again light duty.

The standard 4.11 (Different from 4.1 axle) axle was used in Herald 1200, Herald 13/60, Spitfire up to Mk3, Vitesse 6 (1600), Toledo and Dolomite 1300. Again light duty.

The standard 3.63 axle was used in the Spitfire 1500, Late Dolomite 1500, Dolomite 1850 and 4 speed TR7. Again light duty.

The rare standard 3.27 axle was used on non overdrive GT6. Again light duty. 

In basic terms the light duty axles are derived from the Standard 8. The heaver duty type was derived from the Standard Vanguard.

Any standard light duty axles/diffs should be avoided if you are going to use them in competition work.

I get my anorak and go,

Dave 

 

Edited December 13, 2024 by DaveR

[Dave McDonald]

I think the 3.9, 4.1 and 4.3 cwp’s that fit the TR diff were from the 2000 and 2500 saloons. 
I think the 4.875 was from the Atlas van. 
Dave McD

[DaveR]

14 hours ago, Dave McDonald said:

I think the 3.9, 4.1 and 4.3 cwp’s that fit the TR diff were from the 2000 and 2500 saloons. 
I think the 4.875 was from the Atlas van. 
Dave McD

Hello Dave, Yes the 4.875 was also used in the Atlas van along with the 948cc Standard 10 and Herald engine in low compression form!

Dave 

[MichaelH]

Ratio 4.875 was in my diff with LSD and survived single venue stage rallies and several years of racing

So may be light weight but seemed reliably strong enough

MichaelH

Edited December 17, 2024 by MichaelH

[DaveR]

On 12/17/2024 at 11:33 AM, MichaelH said:

Ratio 4.875 was in my diff with LSD and survived single venue stage rallies and several years of racing

So may be light weight but seemed reliably strong enough

MichaelH

Hello MichaelH, I would guess it had some serious up grade work done on it.

Dave

[TRTOM2498PI]

26 minutes ago, DaveR said:

Hello MichaelH, I would guess it had some serious up grade work done on it.

Dave

The TR, CWP's are certainly strong. Mine has over 300lbs ft torque going through the back wheels.

[MichaelH]

Hi Dave

In 89mm piston form when rallying I am sure that it never produced anywhere near that sort of torque only rated 205 BHP on Peter Burgess dyno

The only special work done on it was to check the mesh between crown wheel and pinion very carefully and to torque the crown wheel to the LSD exactly to the correct torque and to loctite it.

I know cos I built it myself- and it ran on Castrol Hypo LS oil

MichaelH

 

[DaveR]

Hello MichaelH, I agree it's the torque that generally is the problem with the Standard 8 based diffs. No matter if it works for you then no problems.

Dave