is this a strong or weak spitfire diff?
Discussion
They never made a "strong" diff, the only difference were the ratios. Depends on its useage, when I was racing years ago, we could never put more than 200 bhp through one, as they went bang fairly quickly. If its for use in a herald based car with a mild to semi race tune , it should be fine.
If you want a strong diff. for a Spitfire - fit a Subaru one!
http://www.triumphcars.com/current/fm70893u/subaru...
http://www.triumphcars.com/current/fm70893u/subaru...
I'm only going to be running tiny tyres (can you still get 135 or 145 by 13 tyres?) and as the strength is dictated largely by the grip you generate I was hoping to get away with the stock diff if using non-grippy tyres. Are they really that fragile? surely not everyone with tuned spits swaps the diffs out?
My own Spit had around 135bhp and I used a standard diff with Herald Courier ratios (4.55:1 IIRC), never gave me any problems in the 8 or so years of competition, with the last 3 years being on yoko slicks.
The vitesse I drove for `Totally Triumph` was putting out over 200bhp and that did keep breaking the diffs, mainly due to the torque obviously. Max ended up putting in a Quaiffe and that cured it.
You are correct, torque is only generated based on grip level, so on road or even trackday tyres a standard diff will do just fine.
ETA - yes 145x13 are still available.
The vitesse I drove for `Totally Triumph` was putting out over 200bhp and that did keep breaking the diffs, mainly due to the torque obviously. Max ended up putting in a Quaiffe and that cured it.
You are correct, torque is only generated based on grip level, so on road or even trackday tyres a standard diff will do just fine.
ETA - yes 145x13 are still available.
Edited by Rich7se on Friday 19th June 18:30
99% certain it's a 3.89 from a Spitfire IV, about as strong as they come.
Interestingly enough late Spit 1500 diffs (77 on) had a stronger carrier, which was let down by the roll pin used as cross lock pin. This pin is often broken and can allow the cross pin to come out with disastrous consequences.
In a fit of genius BL also fitted cardboard thrust washers under the large diff gears, when these disintegrate the diff suffers from excessive play which leads to teeth off the crownwheel.
A quaife LSD carrier is indestructable and without backlash meaning the crownwheel and pinion is much less likely to fail.
Also don't forget filling the diff with GL5 gear oil can result is the copper thrust washers failing, which leads to lots of play and teeth off the crownwheel.
Interestingly enough late Spit 1500 diffs (77 on) had a stronger carrier, which was let down by the roll pin used as cross lock pin. This pin is often broken and can allow the cross pin to come out with disastrous consequences.
In a fit of genius BL also fitted cardboard thrust washers under the large diff gears, when these disintegrate the diff suffers from excessive play which leads to teeth off the crownwheel.
A quaife LSD carrier is indestructable and without backlash meaning the crownwheel and pinion is much less likely to fail.
Also don't forget filling the diff with GL5 gear oil can result is the copper thrust washers failing, which leads to lots of play and teeth off the crownwheel.
Gassing Station | Triumph | Top of Page | What's New | My Stuff