Advice on fitting rear springs please

[tr6fan]

My TR6 has a CV conversion and telescopic springs on the rear. I thought that undoing the shock absorber would let the trailing arm drop enough to remove the rear spring-I have new ones to fit. The trailing arm has hardly moved and is firmly in place, so I'm wondering if I'm missing something or the CV driveshaft is not allowing the arm to drop. I was hoping not to undo the driveshaft as the torque on its retaining nut is so high-anyone had the same experience? Any advice gratefully received!

[colin3511]

I'm afraid you need to remove the cv joint each side. I got supplied the incorrect springs so I know exactly your dilemma.  There's no way around it. You should also replace the cv nuts too as they have a metal locking tab in the thread that would have been compromised.

Colin 

[tr6fan]

OK thanks Colin, i was hoping for a magic solution but you have kindly confirmed the facts!

[Motorsport Mickey]

Stop !

If you have CV driveshafts undoing the shock absorber would normally allow the trailing arm unlimited downward motion, that could over extend the CV shaft and cause damage. (Sorry for the edit, big fingers)

We have had TRs (TR6 I seem to remember) who have had this happen, the shock absorbers are the only limit of travel, the TRs are quite critical on the CV driveshaft lengths and allowing the trailing arm full droop could overextend it causing interior damage. If you want full droop undo the CV flange on the diff side and then gently prise the flanges apart and remove the bolts, then the trailing arm can reach full droop with no damage or problems. Only 4 bolts and replacing the nuts isn't costly or a problem.

Mick Richards

Edited February 16, 2019 by Motorsport Mickey
Big fingers caused only part post

[tr6fan]

Thanks Mickey, I'll do it back up before I do anything else!

[Motorsport Mickey]

Check my edited post.

Mick Richards

[tr6fan]

That sounds good, might be able to leave the hub nut on then. Thanks.

 

[RogerH]

5 hours ago, Motorsport Mickey said:

Stop !

If you have CV driveshafts undoing the shock absorber would normally allow the trailing arm unlimited downward motion, that could over extend the CV shaft and cause damage. (Sorry for the edit, big fingers)

We have had TRs (TR6 I seem to remember) who have had this happen, the shock absorbers are the only limit of travel, the TRs are quite critical on the CV driveshaft lengths and allowing the trailing arm full droop could overextend it causing interior damage. If you want full droop undo the CV flange on the diff side and then gently prise the flanges apart and remove the bolts, then the trailing arm can reach full droop with no damage or problems. Only 4 bolts and replacing the nuts isn't costly or a problem.

Mick Richards

Hi Mick,

 wouldn't the chassis member stop the CV drive shaft from going too low.  It does when using the standard drive shafts.

 

Roger

[Motorsport Mickey]

Hi Roger, 

I’ve not got an IRS car (TR4) but Niall and I had some correspondence about 2 years ago when one of the Irish lads had CV shaft fail soon after undoing shock absorber for access allowing full droop.

My Stag doesn’t suffer when in full droop but the CVs are about 3” longer and more space behind drums for access. I surmise the TRs are critical because I remember members quoting comparing driveshaft lengths ( various suppliers) and having instruction upon the figures to get. 

I think the shorter CV driveshafts are overall length more critical and whether the standard shafts are small OD and they get away with it I’m not sure.

Mick Richards

[RogerH]

Hi Mick,

I have not played with the CV shaft but can't see how it can drop too far.

Roger

[tr6fan]

Mine doesn't want to drop at all!

[RogerH]

1 minute ago, tr6fan said:

Mine doesn't want to drop at all!

Can you see if the CV Shaft is touching the chassis.

 

Roger

[colin3511]

Roger is correct. The cv joint won't allow the trailing arm to drop enough. I've just done it so it's fresh in my mind. You need to remove the cv joints. Main nut and the four on the diff. Easy enough. It took just over an hour to swap both springs.

Colin

[Motorsport Mickey]

1 minute ago, colin3511 said:

Roger is correct. The cv joint won't allow the trailing arm to drop enough. I've just done it so it's fresh in my mind. You need to remove the cv joints. Main nut and the four on the diff. Easy enough. It took just over an hour to swap both springs.

Colin

So does that answer WILL the arm drop enough and the CV driveshaft doesn't hit the chassis ? Why do you need to undo the large Hub nut otherwise ? if you just undo the diff flange 4 nuts and disconnect the driveshaft and leave the hub end connected the trailing arm should make full droop unless...

a) The CV driveshaft isn't long enough to permit full extension of it when connected and full trailing arm droop...OR

b) The driveshaft DOES hit the chassis preventing the trailing arm going into full droop. 

Can you please clarify which does what ?

regards 

Mick Richards

[tr6fan]

The only thing I undid was the shock absorber and the hub wouldn't drop more than a small distance. The shaft is not in contact with the chassis.

[Motorsport Mickey]

1 hour ago, tr6fan said:

The only thing I undid was the shock absorber and the hub wouldn't drop more than a small distance. The shaft is not in contact with the chassis.

That does sound like the shock absorber is being used to limit the trailing arm droop and maybe prevent over extending the CV driveshafts.

Mick Richards

[colin3511]

My experience is that the cv shaft hits the chassis when you disconnect the shock absorber. I would be concerned that the shock obsorber is restricting wheel movement during driving. It maybe fine but worth checking. 

I guess it depends on the spring free length as to if you have to remove the cv joint. I could almost get mine in but I had to remove cv shaft completely. 

Colin

[Rockie51]

I seem to recall that I installed my Goodparts rear springs without removing the CV driveshafts. I have Koni telescopics on the rear and I undid the top bolt and dropped the arm down.

The Goodparts springs may be shorter than standard so easier to install. 

Removing the inner bolts at the diff end should give some extra travel. When you say that the arm has hardly moved, have you tried pushing on it? If the bushes are tight, you may need to encourage the arm to move. 

[tr6fan]

The trailing arm bushes are poly so it is relatively stiff. Undoing the top shock absorber nut equates to me undoing the bottom one I guess-i.e. the shock absorbetr is no longer connected to the arm. There is a lot of resistance if I push down on the arm but I assume I can push it down so the CV driveshaft contacts the chassis without doing any damage to it? If that is so at least I can explore all the travel to see ifthe spring will come out. Since the CV nuts all seem to need replacing every time you do this I am even thinking of undoing the trailing arm mounts instead-any views on that?

Thanks for all the great advice so far chaps, really shows how good this forum is!

Edited February 18, 2019 by tr6fan

[RogerH]

At the beginning of this thread I had considered undoing the T/A bracket bolts.

No problem in undoing the bolts BUT will the CV shaft restrict its  rearward movement in order to get the bolts out of the chassis.

Once out of course the T/A will be able to drop forward, allowing the spring to come out

 

Roger  

[RogerH]

Which CV shaft do you have?

 

Looking at the CDD CV shaft the hub is attached in the same way as the ST unit.

The inner attachment to the diff has nyloc nuts to undo.

Why can't the hub and diff attachment be undone and pulled out as usual?

https://www.classicdrivingdevelopment.co.uk/cats.asp?cID=4&carID=3&page=TR6+CV+DRIVESHAFTS

Roger

[ChrisR-4A]

I have the CCD driveshafts, fitted over 2 years ago and as supplied they are in 2 parts the hub is fitted to the 6 SA studs and the rest of the shaft is passed through from the diff side locating by the splined shaft in the hub and the big nut. I assumed it is not supplied as one piece because part of it will not pass through the SA. If I am wrong I would like to know in case I ever need to take one off.

Whatever you do, DONT FORCE THE SA DOWN as over extending the driveshaft will damage it.

Edited February 18, 2019 by ChrisR-4A

[ChrisR-4A]

One other point, when fitting the CCD driveshafts to a TR a dimension is given between the wheelarch and the centre of the axle which is governed by the length of the telescopic shock., and should not be exceeded. 

That is why the shocks fitted should be those intended for a TR conversion, as in the case of Koni ‘s various extended lengths are available and longer ones could damage the driveshafts. 

If in doubt give CCD a ring, Alistair is very helpfull.

Chris

[tr6fan]

Yes I have the CDD CV shafts and Alasdair has always been helpful, offering to send me some nuts to facilitate the task. If I can reuse the hub nut and the nuts at the diff are just nyloc (someone mentioned metal tabs?) then I have no real issue as I can easily replace nyloc nuts. The driveshaft seems to be the determining factor in the trailing arm not going down and I do not wish to put pressure on it.

[Bill Bourne]

I have the CCD drive shafts and I've done this several times. The easiest way as mentioned is to simply disconnect the shock absorber. Support the trailing arm with a small trolley jack to keep it horizontal. Then undo the 4 nuts at the diff end. then gently drop until resting on the chassis. I suspect you will have to take the rear of the exhaust off to get to one side. Depends on your exhaust set up. That should allow you to just get the spring out. Depends on the spring length and the thickness of your spring collars. On one of my changes when changing springs around, I had to use a small spring compressor just to give me another 1/4 inch. Fiddly, but doable as it's not easy to get both spring compressors on. Do not compress unless safely secured. You shouldn't need to compress very much at all. If you do, then have a re-think before going any further.

 

Best Bill