Sprint Propshaft thoughts

[rvfrc45]

Hi All,
I'm back working on my sprint but I need some advice on the Propshaft.
1) How does the majority of you split the Prop to replace the centre bearing.
2) Has anybody mixed front and rear sections before. IE fitted a manual front to a rear auto section.
I have a good low mileage Auto sprint prop that I could use that has a good central cv joint.
3) I've read that front and rear sections are balanced separately is this really the case.
4) finally anybody know a good Propshaft specialist's in Essex/ East London area.
Any thoughts most welcome.

[xvivalve]

They are balanced as a complete unit.

If you mark the sections prior to disassembly so that you can reassemble in the same axial relationship to each other it should retain its balance, but if you mix and match from two props it will need rebalancing for sure.

Dennis in Suffolk is (was) looking for an auto' prop' for his car as his had gone missing...

As to splitting, I'll photograph the relevant pages from the workshop manual for you in the morning...

[rvfrc45]

Thank you as that will be very helpful, I can't find my own manual since the house move.

[2door-toledo]

Don't know about east London but if you can travel around the M25 a bit (near Heathrow) Propshaft Services at Dockwells Estate, Central Way, Feltham TW14 0RX sorted out my Toledo propshaft including the joints, bearings, and balancing it. Was happy with the service that they provided.

[xvivalve]

Unhelpfully, my workshop manual tells you how to remove the propshaft and replace the universal joints, but doesn't advise how to service the centre annulus bearing!

The late Jon Tilson always praised Feltham Props

[rvfrc45]

Today I found my sprint manual and as you say very little said on the centre bearing/cv joint other than changing the U/J s.
I'm going to fit new U/j s in the original prop and see what its like on the road.
I still have the low mileage auto prop and will leave that alone at the moment. I may sell later if I do not shorten it. So if anybody is interested message me.
Yes I phoned Feltham Propshafts today and said I may need their help in the future but they did sound very professional.
So Thanks again for feed back

[gdc2john]

I've just replaced my centre bearing. Here's how

1 mark both 1/2s of the shaft so they can be assembled with the correct orientation later
2 lever open the collar around the rubber boot with a screwdriver or such and drive off.
3 cut old rubber boot off shaft
4 remove wire ring retainer from inside outer cv and extract the shaft 1/2s apart, taking care not to loose balls
5 clean every thing up with petrol
6 drive inner CV knuckle off shaft, retained by spring ring internally, remove loose balls and ball cup, observe orientation of cup as its not symmetrical
7 remove circlip in by bearing and pull old centre bearing off shaft, observe orientation of bearing
8 reinstall centre bearing around the right way. I had to turn a few mm off the outer spacer to get the circlip on, the new bearing was thicker.
9 fit new rubber boot to shaft. Mini Spares part no GSV1073
10 refit inner knuckle and fill pot joint with grease supplied in boot kit
11 put balls back in knuckle, hold in place with a little grease then insert into pot joint
12 refit inner retaining ring
13 fit boot around the outer side of pot joint, not inside as original, secure with band. I didn't use the original steel cup thing, I cant see any reason
why its needed, Minis don't use anything like that and their pot joints are much more exposed.

Hope this helps
John

[Sprintparts]

9 fit new rubber boot to shaft. Mini Spares part no GSV1073

Have you done any high speed running with this boot fitted?

Most CV boots can't handle the prop speed compared to a FWD driveshaft (depending on diff ratio could be 4 times faster).

Mark

[gdc2john]

No I havent, car still not finished, may have a point, but it was proving very hard to peen the metal retainer on, will just have to wait and see.
The mini boot supplied seems to be quite strong and of good quality. Ive never had one split on my minis both for 100mph plus on the track.

[Sprintparts]

No I havent, car still not finished, may have a point, but it was proving very hard to peen the metal retainer on, will just have to wait and see.
The mini boot supplied seems to be quite strong and of good quality. Ive never had one split on my minis both for 100mph plus on the track.

OK, time will tell.

Just remember that a driveshaft in a Mini is only doing road speed, not engine speed, as in a Dolomite at 6000 rpm in 4th gear. I am sure that a Mini CV boot will survive in most road car applications, but from experience I have had FWD CV boots explode at high speed and it is like a bomb going off under the car.

Mark

[gdc2john]

So why doesnt the original boot explode, I cant see any difference, Other people on here have used these boots.
Just wondering, I dont profess to know everything about them

[Sprintparts]

I don't doubt that the Mini CV boot will work OK in a road car at road speeds, I am still looking for a suitable boot that has been proven to be able to handle 7000+ RPM in 4th gear.

Don't really have any expertise in CV boot design etc, but my best guess is that the OE Sprint CV boot is a small diameter/mass (than a FWD CV boot) and it is mostly contained within the tailshaft CV joint, so it is not as susceptible to centrifugal force.

The larger/heavier FWD CV boot spins possible at around 1000/1200 RPM max, wheel diameter and max speed dependent, so the centrifugal force is no where near the 7000+ RPM tailshaft.

Mark

PS. If some one with more knowledge, or experience cares to pass on what they know, that would be much appreciated.

Mark

[Carledo]

I don't doubt that the Mini CV boot will work OK in a road car at road speeds, I am still looking for a suitable boot that has been proven to be able to handle 7000+ RPM in 4th gear.

Don't really have any expertise in CV boot design etc, but my best guess is that the OE Sprint CV boot is a small diameter/mass (than a FWD CV boot) and it is mostly contained within the tailshaft CV joint, so it is not as susceptible to centrifugal force.

The larger/heavier FWD CV boot spins possible at around 1000/1200 RPM max, wheel diameter and max speed dependent, so the centrifugal force is no where near the 7000+ RPM tailshaft.

Mark

PS. If some one with more knowledge, or experience cares to pass on what they know, that would be much appreciated.

Mark

There is something to be said here about your particular problem. In that there is, as you've mentioned, a world of difference between your track car, maybe without overdrive and capable of achieving 7000+ rpm in direct 4th gear (this gives a road speed, by my guess, in excess of 140 mph with the standard 3.45 axle, something i'm not sure the Dolomite's unfavourable aerodynamics will even permit, even with another 100bhp on tap) and a road car doing somewhat less than 4000 prop rpm at 70mph. Which is the legal max speed limit here in the UK. If you are running a 4.11 diff or some other racing ratio then your situation is even further divorced from normality. Still, I feel your pain and frustration about your inability to obtain a simple rubber boot that is cramping your style!

I admit I don't have your long and substantial track racing experience, being just a trackday dabbler and occasional bracket racing drag racer. Still, my cars are more than capable of sustaining 3 figure road speeds if need be. But I don't run the C/V'd prop, opting for the more conventional 2 piece/3 hardy spicer jointed prop, adapted from either a Toledo or 1500 auto. Is there any homologation regs that would stop you adopting the same design? Or is the diff end mounted sliding joint too weak for your power output? It doesn't bother my cars despite frequent line-lock burnouts on the strip, though I probably have less total power to play with, a burnout like that will provide enough sudden torque to give any driveline a workout!

As to WHY the FWD boots blow up on you, could it be because of air inside getting hot and expanding till the boot can't stand the strain? Literally blowing the boot up like a balloon till it bursts? Also a C/V boot is generally thinner to give a wider range of flexibility over bigger angles (and yes, lower speeds) than the handful of degrees variation in a prop centre joint. It might pay to look at driveshaft inner pot joint boots which are often more substantial and have to endure a smaller range of movement in service.

Just my 2 pennorth, no science, just an old engineer's intuition!

Steve

[gdc2john]

The boot I used is the mini inner pot joint boot. I compared the size and shape of the mini boot and the original boot, I could see no
discernible difference. I'm going with it as in the driveshaft it has a lot less movement than in a mini.
No science, just a gut feeling.

[Carledo]

The boot I used is the mini inner pot joint boot. I compared the size and shape of the mini boot and the original boot, I could see no
discernible difference. I'm going with it as in the driveshaft it has a lot less movement than in a mini.
No science, just a gut feeling.

Y'know I was just showing my age to myself, when you mentioned the inside end of a Mini driveshaft, all I could think of were those awful maltese cross shaped metalastic joints held in by U bolts that all Minis had when I was working on them back in the 70s! Never occurred to me that of course Minis got dragged into at least the 20th century and got proper inner CVs too!

Steve