Rear axle leak

[KWM338R]

Hi All,

I finally have my Sprint back competing State side. Currently doing autocross events. I have slick tyres on the car and after the last event the drums were full of oil. I've read about the gearbox seal modification but am wondering if there is also anything else that can be/has been done to mitigate the problem even more, such as better bearings giving the half shaft better support. I do not have to worry about any racing/homologation rules so am free to modify the axle if it will help.

Regards,
Mark

[gmsclassics]

Hi Mark
I started with the gearbox pinion oil seal modification and found that a vast improvement. However, I never raced with slicks, only circuit classic racing using Toyo and Dunlop treaded race tyres.

At one stage while I was racing I did manage to get hold of an axle that had been modified with support bearings midway along the halfshaft. Apparently that had been a very expensive modification! Unfortunately it didn’t last all that long (less than a couple of years) and then destroyed the C&P as well as the LSD. I do have a poor copy of a drawing that details how this was done.

I’ve never seen or heard of anyone making the thicker diameter Sprint halfshafts these days, but you could try contacting Rob MacGregor at Sprintspeed in the UK, or Ken Wood. He has posted on here but not recently. Both are active in motorsport in the UK.

I ended up modifying a Ford Capri 3L rear axle by welding on the Sprint axle mountings. Didn’t have to change the prop, but modified the Ford pcd on the half shafts to take Sprint wheels. LSD are cheaper and parts are available, as are upgraded half shafts. I used 3J Driveline in the UK for these. No real issues with this modification over many years.

Might be simplest to start with the oil seals and see how you go!

Geoff

[KWM338R]

Thanks for the input Geoff.

I think that is sound advice, start with the seals. I'll give it a go and also look for a small rear axle over here as a potential replacement. I'll probably have to look for something japanese as all the US stuff is just plain massive!

Cheers,
Mark

[shaunroche]

Much has been said on this subject recently and after changing all four seals on my Sprint, still have a leaking off side hub.

After all the effort and cost I've gone to to sort it, all to no avail, it's soul destroying.

I suspect, as has been said here that it's the drive shaft flexing...

https://forum.triumphdolomite.co.uk/vie ... f=4&t=7920

[KWM338R]

Would anyone happen to have the ST halfshaft specs and/or drawing available to share?

Cheers,
Mark

[gmsclassics]

Short answer is no and I've never seen anything. I've relooked through the copies of old homologation papers I have and nothing mentioned other than simply 'uprated rear axle' in Group 2. I suspect this is more of a modern issue as period racing tended to use narrower tyres that slid more than modern sticky rubber we use. Hence it might have been more common in Group2?

Can only suggest you contact the people I mentioned above, also Cambridge Motorsport as I believe they prepare some racing Sprints in the UK. Be interested to see what you can find out.

Geoff

[KWM338R]

I replaced the seals in the axle, it already had the gearbox seals in but I did them anyway. there was no grease in the bearings, i suppose it got washed away by the oil.

Anyway I reassembled carefully and after one autocross yesterday all seems well from the outside. I'll pop the drums off again soon to see if there is any sign of a leak.

Cheers
Mark

PS excuse the condition, it goes better than it looks!

[oldred]

Mark,

I have 'uprated' half shafts that I have fitted in my Sprint axle and I am guessing that it is an ST copy. Axle remaines on the shelf in the garage for a decade but all went in ok as I remember, but remains untested. I would also hazard a guess that Triumph used to raid the parts bin to find suitable bits. We already know that T2000, Stag and TR6 parts are used on the axle.
I have something in my mind from the dim and distant of this half shaft being from a TR4? afterall the leather! oil seal would indicate that its not a new for the 70'S design!
My half shafts do not have the reduced diameter machined over the length of the half shaft. That is to say that over the full length of the half shaft the diameter is exactly the same as the spline? dia.

Hope this helps.


Phil.

[KWM338R]

I've not done anything more with the axle, I'll live with the leak until the end of the season then look at it over the winter.

Thanks for the tip on the TR4 halfshafts, I'll see if I can find one over here to compare.

Cheers
Mark

[trackerjack]

I wonder if a simple spinner that clamps round the shaft might throw the oil before it breaks through.
I never solved the issue on my Sprint and used to soak the brake shoes in brake cleaner and set fire to them and refit Every MOT I would insert a new set of shoes.
With my brake mod I never missed the rears on track because if your going fast enough they are not needed, the fronts do all the work!
Strangely I was only yesterday talking to a current racer who races everything from touring cars to Citroen CV,s and he said they grease the drums on the inside on the Citroen because they don't want it to spin (rear lock up = spin).