Fitting an Isuzu inner CV joint to an Elan Driveshaft

[andrewp]

Although externally nearly identical, the inner CV joint (L-hand side . . . R-hand is assumed identical) of an Isuzu Impulse 1990-1991 or Stylus 1991-1992 will not fit on an Elan M100 driveshaft. The driveshafts are splined differently. Isuzu has coarser teeth at the inboard end, Lotus has finer teeth.

However, if you are patient and enjoy a challenge the two can be made to work together. Disassemble the Lotus inner CV joint. You will find a steel tripod piece (retained by a snap ring). On each extension there will be a roller which runs on needle bearings. This roller has a distal cup-shaped washer and a wire clip which holds the loose needle bearings secure. It also has a D-shaped special inner washer.

It is a difficult task to pry the wire clip up and work it free of the cup-shaped washer. Expect this step to be the most challenging. I used two 90 degree picks and a jewelers magnifying headset. It took slightly less than an hour to do all three ends . . . but you get better at this with time.

Once apart you will have one tripod joint, three special base washers (D-shaped), three roller bearings, three cup-shaped washers, three wire clips, and about 100 tiny needle bearings. Keep everything separate.

Now do the exact same disassembly to the new Isuzu inner CV joint. You will notice that the rollers are larger in diameter on the Isuzu joint. Also the needle bearings are longer and there is no special base washer on the end of each tripod lobe (or there wasn't on mine).

What you need to do is install:
the special base D-shaped washer (round side up),
the longer Isuzu roller bearings,
the larger Isuzu rollers,
the Lotus cup-shaped washer,
the Lotus wire clip,
All on the old Lotus tripod.

The tripod will now slide on the Elan driveshaft splines and have larger rollers (spaced slightly wider) than the Lotus ones. Fit the new Isuzu inner CV joint and you are good to go.

Why do this? A new Isuzu driveshaft is $42 Canadian (maybe $30 US) from Rock Auto. It comes with a steel driveshaft (albeit the wrong length for an Elan), new inner and outer CV joints, and new boots. The supply of new Lotus Elan M100 driveshafts have virtually dried up. US suppliers are asking $870 (US) for a new Elan inner CV joint. This solves that supply -and price- issue. Also the Isuzu inner CV joint is 5% wider, with 5% larger rollers, so it should be more durable, assuming the metal is comparable with the Lotus original.

You need to fit the Isuzu CV boot. Only the wider Isuzu boot will fit this hybrid inner CV joint.

Hope this helps some owners.

Andrew P. in Edmonton

[FunElan]

very nice work. This should be in the wiki

[tigerdog]

well done!

[Tuga2112]

i just read this 3 times to try and understand what you done.

im just repeating a summary of what i understand, to clarify

you took the tripod end of the Elan shaft. disassembled it. and replaced the rollers and the bearings with the same parts from the isuzu tripod. and then, used the modified tripod to couple the Elan's shaft with the isuzu CV joint ?

did you happen to take note of the teeth and measurements of the tripod that you ended up installing ?

[andrewp]

The spline count of the shaft itself differs between the Isuzu and the Lotus unit. Lotus uses fewer splines.

So it would be impossible to mount the Isuzu "tulip", with new bearings, onto the Lotus shaft.

But the tulip can be taken down to its 150 (or so) small bearing parts and then everything can then be built up onto the bare Lotus tulip. There are tiny differences like the shape and size of the cup washers on the Isuzu unit . . . but so long as they are assembled as they were, everything will transfer onto the Lotus tulip. As noted, the three Isuzu roller bearings are slightly larger diameter . . . but so long as you use a new outer Isuzu CV housing, all works perfectly.

Andrew P. Edmonton, Alberta, Canada

[andrewp]

I did not do a spline count between the Lotus and Isuzu shafts/tulips. This info was not deemed critical to me at the time . . . but I can definitely see that it is, now.

I will do a spline count the next time I need to perform this swap.

[Giniw]

Hi,
I'm not sure either of what you kept from the original parts, so I am asking with an illustration just to be sure.

What I understand:
- You took your used lotus driveshaft,
- You kept only the Lotus shaft (grey, noted "midshaft" on the photo) and also the tripod mounting (yellow, noted "tripode" on the photo)
- You installed the Isuzu rollers (red), needles (cyan), washers (purple) on the original Lotus yellow tripod
- You used the Isuzu tulip (green)

driveshaft.png

Do you confirm this?
Are both Isuzu tulip suitable? I would imagine the LH one that is going in the differential has the same splines, but is the RH one that is mounted on the intermediate shaft the same too?

https://www.rockauto.com/fr/moreinfo.ph ... 73&pt=2288
https://www.rockauto.com/fr/moreinfo.ph ... 73&pt=2288

From the photo I would say the RH one is just one part and the RH intermediate shaft and the RH tulip are a single part, not like on the Elan with a female tulip?

[chrispy350]

Hi - I'm wondering if there's any chance this thread is still alive.
As I have a worn-out inner CV (passenger side, in the US), I tried to do this swap. Ordered an Isuzu replacement axle and disassembled the tripods, etc.
Problem is that the Isuzu rollers will not fit onto the original Lotus tripod: the inner diameter of those rollers is about 2mm larger than the stock Lotus parts. The Isuzu tripod of course has the wrong spline. The Isuzu rollers are a 'must' for using the Isuzu tupip.
Confused, as this plan seems to have worked for some folks.
Can anyone enlighten me?
Thanks!

[Tuga2112]

that description seems like you need to spend time researching tripods with larger bearings.

from my experience in that field. i found theres no place online that just lists what they are and their details. you have to manually find out which cars have the same spline design, and then look at the details of every bearing that is a cross reference to them. and the cross references to the bearings themselfs.

you can also contact a motorsport specialist or garage with a lot of experience in high tuning and ask them. they may have the knowledge from prior experience to guide you, or supply you with something.

researching online for them is extremely time consuming. i spent 3 weeks every night more than 3 hours googling about when i was looking into it.

[dapinky]

I also spent a long time researching 'options' when the OE driveshafts went obsolete, and ended up without finding any real replacement.

What I did find, though, is that the Lotus 'sockets' for the inner joint are bespoke items.... and the good thing is that they rarely actually wear to an appreciable amount (unless I suppose, the car has been run with no grease). The usual wear is in the tripode part of the male fitting - and these are still available to buy.

The main reason for failure appears to be incorrect grease used during ownership/repair/maintenance..... probably when replacing a damaged rubber boot. Not many garages (or owners) realise that you should not use a 'standard' CV joint grease (because it is technically NOT a CV joint!), and must use a compatible grease which is supplied by the sole manufacturers of the OE units - GKN.

It is all down to the melting point of the grease and it continuing to perform without dripping out of the tiny rollers - don't ask me any more than that - it's the only bit I understood having read a lot of words!!!

So, to sum up, you need to get hold of a GKN MS3H002 (it has a 1" diameter with 30 splines) - I use Raceparts.com for them (UK & USA websites!)......... then use the proper grease - which I get from Merlin Motorsports

There are a couple of other threads where it is all discussed viewtopic.php?f=48&t=28891 & viewtopic.php?f=48&t=30403

The outer joints are completely different, and use a 'standard' GM mechanism inside a slightly machined GM splined housing...... as such they can be repaired, but I've yet to find one that needs it, because these use standard CV grease and just don't really wear a lot as the correct stuff is used when the boots are replaced.

However - should anyone be able to find a suitable 'off-the-shelf' unit which can be easily adapted for the Elan, I'd love to hear about it, as the GKN parts are getting far harder to find these days than they were 10-20 years ago, and more shafts are going to wear out in the future.