I'm on record as being a fan of the Rover Diff, stating that the diff itself is pretty bomb proof and that all it needs is stronger output shaft material.
That's drawn in part from knowing that the better material approach works for the long input shaft in the extension case. And from never having heard of a diff carrier and sun wheels etc being in distress.
That view has never been seriously challenged because no one has tackled making the output shafts in better material. That's for good reason. The shape as seen in the photo - nicked from Clive Osborn - is such that you either need a very large initial billet and a lot of machining, or you need a friction weld between output flange and shaft. Expensive.................
Now Fraser Stark - looking at a 300 bhp plus engine installation - has actually taken an output shaft to a machine shop. The crit of the machine shop is a bit devastating.............
"They said there aren't enough splines to share the load sufficiently creating pressure points on the shaft, the step up on the splines is a weak point and they're not wide enough overall. They recommended more splines, no step up and wider outputs shafts."
Oh dear.
That means you would need to have the female portions of the splines on the diff carriers modified too.............. And you'd probably need new bearing housings to bolt on the side of the diff.............
In gloom, I looked back at the diff's history. Essentially it's a standard 50's Rover diff modified to sit in an IRS casing and to accept cornering loads into the diff casing. Design signed off in around 1958 to suit a 90 bhp four cylinder......... The only subsequent changes are the ribbed casing for better cooling and an extra pair of sun wheels......... Which could be seen as bodges to avoid a total redesign for P6B. Hmmm
Especially when you consider that the people with a motive to do something are people with big engines, it looks like what is needed is a full set of new LSD internals including input shaft and output shafts and probably output shaft bearing housings. Only the main and extension shaft housings carried over.
There's no debate that that is going to be seriously expensive..................
So what to do.............??????
Most people are going to be happy simply with a supply availability of output shafts to replace broken ones............ Supply of secondhand diffs is still good enough, just about, to avoid doing that for a while................
Those wanting serious use of serious performance cars therefore have a problem. I still, despite much searching, have only identified one diff - the Jag - that is capable of using inboard brakes and accepting the side forces generated by cornering. Any other solution demands a wholesale rear suspension change. That would be a pity, as it would lose one of the most characterful aspects of the car - and one that is shown to be outstanding at putting the power onto the tarmac. To this day, there's nothing to touch the P6 de Dion in that respect.
I'm only aware of three well described Jag diff transplants. Simon Owen's, the 5000TC in the USA and now Quattro's (modelled on the 5000TC installation?). I'm waiting with baited breath for news of some in service experience of Quattro's......................
Does anyone else have any ideas for alternative diffs or of other ways of installing the Jag diff................?????
Or is a design commission to Quaiffe called for.................??????
That's drawn in part from knowing that the better material approach works for the long input shaft in the extension case. And from never having heard of a diff carrier and sun wheels etc being in distress.
That view has never been seriously challenged because no one has tackled making the output shafts in better material. That's for good reason. The shape as seen in the photo - nicked from Clive Osborn - is such that you either need a very large initial billet and a lot of machining, or you need a friction weld between output flange and shaft. Expensive.................
Now Fraser Stark - looking at a 300 bhp plus engine installation - has actually taken an output shaft to a machine shop. The crit of the machine shop is a bit devastating.............
"They said there aren't enough splines to share the load sufficiently creating pressure points on the shaft, the step up on the splines is a weak point and they're not wide enough overall. They recommended more splines, no step up and wider outputs shafts."
Oh dear.
That means you would need to have the female portions of the splines on the diff carriers modified too.............. And you'd probably need new bearing housings to bolt on the side of the diff.............
In gloom, I looked back at the diff's history. Essentially it's a standard 50's Rover diff modified to sit in an IRS casing and to accept cornering loads into the diff casing. Design signed off in around 1958 to suit a 90 bhp four cylinder......... The only subsequent changes are the ribbed casing for better cooling and an extra pair of sun wheels......... Which could be seen as bodges to avoid a total redesign for P6B. Hmmm
Especially when you consider that the people with a motive to do something are people with big engines, it looks like what is needed is a full set of new LSD internals including input shaft and output shafts and probably output shaft bearing housings. Only the main and extension shaft housings carried over.
There's no debate that that is going to be seriously expensive..................
So what to do.............??????
Most people are going to be happy simply with a supply availability of output shafts to replace broken ones............ Supply of secondhand diffs is still good enough, just about, to avoid doing that for a while................
Those wanting serious use of serious performance cars therefore have a problem. I still, despite much searching, have only identified one diff - the Jag - that is capable of using inboard brakes and accepting the side forces generated by cornering. Any other solution demands a wholesale rear suspension change. That would be a pity, as it would lose one of the most characterful aspects of the car - and one that is shown to be outstanding at putting the power onto the tarmac. To this day, there's nothing to touch the P6 de Dion in that respect.
I'm only aware of three well described Jag diff transplants. Simon Owen's, the 5000TC in the USA and now Quattro's (modelled on the 5000TC installation?). I'm waiting with baited breath for news of some in service experience of Quattro's......................
Does anyone else have any ideas for alternative diffs or of other ways of installing the Jag diff................?????
Or is a design commission to Quaiffe called for.................??????
