GT6 CV Driveshafts Classic Driving Development

[Stratton Jimmer]

Having spoken to a few people and read extensively about it, I have decided to do away with the rotoflex on the six and fit CDD CV shafts. Just wondering if anyone in the Swindon area has a rear spring lifter that I might borrow when I come to do the job in early October? If anyone is interested, I will photograph the whole job from start to finish and publish it here. Let me know or I will keep quiet!

[Nigel Clark]

The spring tension can be safely released without the need for a spring lifter.

Disconnect the rear dampers, allowing the rear suspension to drop fully (handbrake cables and brake hoses should already have been disconnected). Take out the two centre studs from the spring clamp plate (which remains firmly held by the four remaining studs at the corners). Screw a pair of 6" long 3/8" UNF studs into the centre holes and wind nuts down these long studs onto the plate.

Undo the nuts on the four studs at the corners. Now gradually wind the nuts back up the long centre studs, slowly releasing the spring tension. Reverse the process when refitting the spring.

Nigel

[Stratton Jimmer]

Thanks Nigel. I can see that that would work and would allow both sides to be done with one operation but is the job easier with the lifter?

[Nigel Clark]

I've never used the spring lifting tool so can't say which method is easier.

BTW, I have the CDD shafts on my GT6. Excellent kit, fit and forget. But take care to check the shimming and get correct end float on the rear hub bearings. It's critical.

Nigel

[NonMember]

The spring lifter is quite easy to use, one side at a time. Nigel's method is OK if you've got good access to the top of the diff, but if there's an occasional rear seat fitted then it may be a hassle to get to it. Worse on a Spitfire as the fuel tank's in the way.

[Stratton Jimmer]

Good to hear of the CDD shafts in use. I think I will go for a spring lifter as I have taken a good look and access to the diff casing is not easy as Rob suggests. Sound advice about the shimming which I will adhere thank you.

[Stratton Jimmer]

Finally got round to doing the first of the two drive shafts this weekend. One shaft (offside) has a damaged rotoflex doughnut while the other is fine hence I decided to do this side first. I had purchased a spring lifter from the club shop and it has proven to be very useful. Everything came apart reasonably easily and the old drive shaft was "drifted" out with a club hammer. I was half expecting to find some shims on the splined end of the shaft but there were none. The fitting notes from CDD suggested that there should be some but looking at the drawing in the Triumph manual (4. 120) doesn't show any other than those within the hub.

I took the opportunity to replace the bushes and fasteners usng the bush kit from the club shop and the nut/bolt/washer set from James Paddock. One minor snag with the bushes is that they do not have totally flat flange faces which means they sit about 1mm wider than they need to be. The old bushes were drifted out using an old 11mm socket to get the steel insert moving and then finishing it off with an old screwdriver (which broke about 35 years ago) that is only usable for drifting. Inserting the new bushes was easily done with a length of threaded bar, two nuts and a couple of decent size washers. That extra mm of width was annoying due to the very tight fit of the components. I did manage to do it but it was quite time consuming and fiddly. Once one face is in by a smidgen I had to get the opposite face in by a similar smidgen and then both could be masaged into place.

Anyone tackling this job should make sure they have a decent "rat tail" device for lining up the bushed holes before trying to insert the bolts. This renders it easy to do. Once the new drive shaft had been fitted to the hub, I offered it up but it wasn't possible to get it in to place due to the spring lifter being in the way. It is necessary to lift the spring to get enough clearance between it and the chassis. A pile of blocks and a bottle jack solved this problem. I would have used an axle stand but both were in use already. With the chassis to wishbone, the chassis to vertical link, the spring eye, and the radius arm all now reconnected loosely, the hub has to be raised to the normal road height (approximately) in order to get the diff flange bolt holes to line up. There is only one rotational position of the diff flange that allows the bolts to be inserted and also allow access with a spanner. There is a torque setting for these bolts but my torque wrench couldn't get near the bolt heads and so I applied the standard engineering practice of using the right size spanner (9/16 AF) and getting them as tight as I could by hand. This necessitated having a glamorous assistant stopping the hub from rotating with a bar placed across the wheel nuts (which had been refitted to the studs to protect them from any possible damage).

Torqued everything back up then found that bleeding brakes was "fun" as the rear bleed nipples are a sod to get at where they are angled back towards the vertical link. However, it was done and with road wheels refitted, a test run showed no alarms. For the time being, I am going to run with one rotoflex and one CV shaft. Does anyone forsee any problems with that arrangement albeit it is only until I can find the time to do the nearside CV shaft?

 

[Colin Lindsay]

22 minutes ago, Stratton Jimmer said:

Does anyone forsee any problems with that arrangement albeit it is only until I can find the time to do the nearside CV shaft?

Only generally, as in the case where you replace one shock absorber or one front road spring instead of the pair - it may work but it's not the best. Keep the speed down, be careful cornering, and it should be ok for a short while, but replace the other asap for real peace of mind. 

Otherwise, that's a good job, well done and let us know how it performs when complete.

[Stratton Jimmer]

Thanks Colin. I will post some more pictures once the film gets back from the developer. Meanwhile I  will drive with some caution until all is sorted. 

[Alex59]

On 10/24/2021 at 5:26 PM, Stratton Jimmer said:

 I was half expecting to find some shims on the splined end of the shaft but there were none. The fitting notes from CDD suggested that there should be some but looking at the drawing in the Triumph manual (4. 120) doesn't show any other than those within the hub.

 

You'll find some shims if the bearings need it to respect the end float of the hub.

Sometime when you are lucky the bearings doesn't need it. Depends of the tolerance of the bearings, of the half shaft and the hub.
Or maybe someone before you, work ont the hub and don't care about the end float.

[Stratton Jimmer]

Thanks Alex. From reading / wading through the many posts in the fora about end float, I figured that that might be the case. I shall be doing the nearside driveshaft in the coming days and will see what that reveals.

[Alex59]

i colorized this sheet when i changed my donuts. I did it in order to undertsand why the end float is needed and how to set it.
On this draft, you will see if the spacer and shims are not enough, you will tight on the bearing and you may damage the ball of the bearing. If the spacer and the shims are too importants, the balls of the bearings will not be in contact with their races. And you will have a possible rotation of the hub (top to bottom). That's why the end float is so important.

[Stratton Jimmer]

That is useful Alex as the workshop manual doesn't show the assembled hub in this way, only the exploded diagram (p. 4.120). What ths diagram doesn't seem to show though is the inner oil seal unless it is here described as a "spacer".

[Alex59]

The spacer is not the inner oil seal, the spacer is an annular metal piece (like a fat shim).

A picture of a spacer (found on another forum)

 

The inner seal is on the picture see below . This diagram is avaible on the workshop manual p 3.124

[Stratton Jimmer]

Each shaft has one of those but in the book it is designated as being an oil seal. I will see if I can post a photo of the drawing...

[Stratton Jimmer]

[Alex59]

On the drawing you posted, the spacer and shims are N°36 & 37.

 

[Stratton Jimmer]

I see it now thanks Alex.

[Stratton Jimmer]

The nearside drive shaft has now been fitted. It took less than half as long to do as the offside one. That is the benefit of hindsight and having found out all of the pitfalls already. Bleeding brakes is the next job followed by carb tuning (HS4s) but meanwhile there's a meeting of the North Wilts branch tomorrow evening. Yet again there were no shims, only a single spacer but the endfloat was comfortably within limits.