Lotus Elan

CV Driveshaft Question

PostPost by: roblotus79 » Wed Nov 20, 2013 2:55 am

All,

I have read through a lot of all the threads here regarding CV driveshaft conversions and I have a couple of questions as my donuts are shot and want to go the CV route. So any help would be great:

1) Are the products supplied by Sue Miller and Paul Matty actually the same?

2) RD enterprises supplies a complete kit that also includes new differential output shafts ($1650). Is there a real concern about the strength of the original differential output shafts and the load they see in the absence of the donuts to buffer the shock?

I've got a 69 plus 2 with a rebuilt engine to big valve head specifications.

Cheers

Rob
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PostPost by: stugilmour » Wed Nov 20, 2013 3:40 am

roblotus79 wrote:
.... Is there a real concern about the strength of the original differential output shafts and the load they see in the absence of the donuts to buffer the shock?

Rob


Rob, I fitted the RD kit and very happy. I believe the stock output shafts were strengthened over the Elan product run, but couldn't find a reference in by Robinshaw. At any rate, I understood our cars came with the stronger shafts. That said, when I removed my original shafts they were distorted in a spiral, so I was pleased the kit included replacements. :shock: The replacement shaft has a CV flange face which mounts the CV nicely.

The kit is pretty heavy, so shipping from GB might be expensive?

If ordering from Ray, have him put "Parts for vintage automobile - over 25 years old" on the packing slip and no duty, just GST.

HTH
Last edited by stugilmour on Wed Nov 20, 2013 3:50 am, edited 1 time in total.
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PostPost by: rgh0 » Wed Nov 20, 2013 3:48 am

The strengthened diff output shafts came around 1970 IIRC so a 69 Plus 2 probably had the older style weaker shafts. The CV conversion itself is not the problem as the early diff output shafts fail overtime with the donuts or Cv's. How fast they fail just depends on your driving style and how many hard starts you do. Most of the original weaker shafts if not replaced by now will be showing signs of twist in the splines unless the car has had a very easy life.

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PostPost by: peterako » Wed Nov 20, 2013 9:37 am

Hi Rob,

I think that Sue supplies (or used to) the CV kit (Mick Miller CV Conversion Kit) to Paul Matty.
If it's still the case then the answer to your first question is 'yes'. But Sue would better inform you.

I put Sue's (Mick's) CV Driveshafts in my 1973 +2 about 40,000 miles ago.

They have been one of the best upgrades I have made to my car and are still going strong.

Take care,
Peter
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PostPost by: roblotus79 » Wed Nov 20, 2013 3:41 pm

Thanks everyone!
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PostPost by: pharriso » Wed Nov 20, 2013 4:01 pm

There is a huge difference in price between the Sue Miller CV conversion (was 450 GBP = $750 2 years ago) vs. the RDEnt drive shaft conversion ($1550).
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PostPost by: William2 » Wed Nov 20, 2013 5:35 pm

Just to throw in a curved ball, I have used the Tony Thompson solid driveshaft kit and been very pleased with it. Some people prefer the Spyder version as it retains one doughtnut and therefore you keep some of the cushioning effect.
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PostPost by: frearther » Wed Nov 20, 2013 6:31 pm

I installed the RD unit on my S2, and I'm glad that it included the differential output shafts; the originals were twisted 5-6 degrees.

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PostPost by: nomad » Thu Nov 21, 2013 2:06 am

I had planned on making my own CV drive shaft's but if the diff output shafts are that weak I may have to rethink that.
Can one buy just the strengthened diff output shafts ready to bolt up to CV joints from anyone?

Kurt.
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PostPost by: StressCraxx » Thu Nov 21, 2013 3:49 am

nomad wrote:I had planned on making my own CV drive shaft's but if the diff output shafts are that weak I may have to rethink that.
Can one buy just the strengthened diff output shafts ready to bolt up to CV joints from anyone?

Kurt.
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Hello Kurt,

The CV axle kits supplied by Ray at RD Enterprises or Jeff at JAE Parts include new high strength diff output shafts. They are based on the later half shaft design, but a better alloy and heat treatment. I am planning on doing this conversion myself this winter and adding a 3.55/1 Quaife diff.

There are pics on Ray's web page under the Elan parts page link.

I have no relationship with either, other than a satisfied customer.

Regards,
Dan Wise
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PostPost by: AHM » Thu Nov 21, 2013 10:24 am

Rob,

Technically - I believe that the shafts that include the input shaft and stub axle do away with the adapter plates - less bits less weight. An advantage of this is that the CV joints can be further apart, so the articulation angles are lower for the same suspension movement. With the adapter plates they are closer together and right on the limit. Hence some discussion here about suspension droop limiters.

Kurt,
All the information you need to make the shafts can be found on this site - Rohan has given the useful dimensions in several threads, and there is a drawing of an adapter plate. There is also an article somewhere about making the diff input shaft that fits directly to the CV joint. Easy enough to do using second hand shafts and joints. Similarly you could get the shafts made to your spec.
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PostPost by: dlbutler » Thu Nov 21, 2013 12:13 pm

I installed the r.d. kit after breaking an inner shaft. The only problem was the spring and damping rates needed to be increased to get back to where the suspension was with the donuts. Also, the CVs will be happier if you also install the dampers that allow less droop. The stock ones could cause the CVs to bind when going over a "yump."
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PostPost by: RichardHawkins » Thu Nov 21, 2013 3:53 pm

Rob,

I did my own conversion. Difficult and time consuming. If the R Dent conversion includes new diff output shafts that have a round flange for the CV joint to attach to, that will reduce the angle that the CV joint needs to move through, by not needing an adaptor. Does this conversion also include replacement hub stub axles? If so this would help further.

What I discovered is that the original Lotus shafts with their 3 bolt "spider" flanges are not concentric with the shaft axis. This probably did not matter when using rubber Rotaflex joints as the rubber will move. Some of my friends have found that they cannot get a bolt to pass through the original Lotus drive shaft into the Sue Miller adapter, and have had to file the bolts or studs to fit. I cannot remember whether Sue uses bolts or studs. From my limited experience of my own car the error is with the Lotus original parts. This may explain part of the reason why the R dent option is more expensive.

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PostPost by: stugilmour » Thu Nov 21, 2013 5:34 pm

RichardHawkins wrote:
.... Does this conversion also include replacement hub stub axles? If so this would help further.

What I discovered is that the original Lotus shafts with their 3 bolt "spider" flanges are not concentric with the shaft axis. This probably did not matter when using rubber Rotaflex joints as the rubber will move. Some of my friends have found that they cannot get a bolt to pass through the original Lotus drive shaft into the Sue Miller adapter, and have had to file the bolts or studs to fit. I cannot remember whether Sue uses bolts or studs. From my limited experience of my own car the error is with the Lotus original parts. This may explain part of the reason why the R dent option is more expensive.

Richard Hawkins



Richard, the RD kit does not include the hub stub axles. I had the same problem with them installing my RD kit. I relieved the holes on the hub stub axles slightly to get the CV to fit. Agree this appears to be an issue with the Lotus stub axle dimensions, and new shafts with a CV flange would be bonus. The access to relieve the holes is OK IIRC; I originally installed them with the body off though. The CV has three countersunk socket head screws; need a ball shaped metric Allen wrench to back the screw up while tightening the Nylocs at the shafts.

The RD kit uses Volkswagen CV's. I had to replace a boot and only issue with getting a replacement was finding the correct CV from the Volkswagen product line. Once I removed the shaft and brought it in to a VW independent it was no issue to match up.

For installation you may need a special 'double square' male socket to undo the CV fasteners. Rest of install is pretty straight forward, although the circlip for the diff shafts was a bit fiddly, and I was worried about the splines damaging the seal. I would also consider doing the hub bearings at the same time if you have any concerns with them or they are of unknown age; if you don't have access to a press suggest taking the entire hub in for bearing fitting.

For the Plus 2, I found no issues with CV binding at full droop. I believe (from previous threads) the Sue Miller Plus 2 shafts were OK as well, but agree the replacement diff shafts should help a bit in this regard for the Elan.

Lets not forget Col's shaft kit from down under as well. He indicates no issue with full suspension travel on his kit.

http://www.elantrikbits.com/

HTH
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PostPost by: fatboyoz » Thu Nov 21, 2013 11:23 pm

Kurt,
Tony Thompson Racing (TTR) has them: http://www.tonythompsonracing.co.uk/pricelist.pdf
so has Kelsport:
http://www.kelsport.net/parts/products. ... ctionID=45
Kelsport also has CV driveshafts:
http://www.kelsport.net/parts/products. ... ctionID=27

Cheers,
Colin.


nomad wrote:I had planned on making my own CV drive shaft's but if the diff output shafts are that weak I may have to rethink that.
Can one buy just the strengthened diff output shafts ready to bolt up to CV joints from anyone?

Kurt.
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