Vibrations in the rear

[John Morrison]

I'm thinking this is drivetrain, try the neutral trick, and get back to us.

John.

[Z320]

Sorry me for asking,

what is the conclusion from the neutral trick?

While the car drives without load everything is still spinning, powered from the wheels?

Ciao, Marco 

Edited September 2 by Z320

[Andy Moltu]

U/J?

Left field one - wrong length diff pin? Do up the nuts, but the unthreaded part of the diff pin is a bit too long and the mounting rubber doesn’t get compressed/restrained adequately.

[Z320]

The only difference I can see of the neutral trick is

the prop shaft driven with power or without power —> U/Js

[Charlie D]

2 hours ago, Z320 said:

While the car drives without load everything is still spinning, powered from the wheels?

Yes, but the force on the UJ's is in the opposite direction, (because they are driven by the wheels, and not by the engine).

That may make a difference.

(I think...)

Charlie.

[glasgow4a]

Has the prop shaft been fitted correctly i.e sliding part at gearbox end cheers Ian.

[Mike Herlihy]

Bit of an odd one but had this on my own car, went on for years. Tried a friend's wheels and tyres, new propshaft, new standard driveshafts, new standard hubs, CV driveshafts as a last resort. Eventually traced to the output flange on the overdrive. It had obviously been dropped at some point and bent the flange. It was only obvious when a dial gauge was set up and used to check the runout. Fitted a replacement flange and all was fine. 

[rcreweread]

4 hours ago, Mike Herlihy said:

Bit of an odd one but had this on my own car, went on for years. Tried a friend's wheels and tyres, new propshaft, new standard driveshafts, new standard hubs, CV driveshafts as a last resort. Eventually traced to the output flange on the overdrive. It had obviously been dropped at some point and bent the flange. It was only obvious when a dial gauge was set up and used to check the runout. Fitted a replacement flange and all was fine. 

Mike - that's a very good point, but the same could just as well apply to the other 3 output flanges in the drive line ie input and output flanges on the diff, and I suppose it would also be worth checking the trueness of the rear hub flanges.

One other thought - the gearbox output flange looks the same as the saloon ones but the PCD is very slightly different - I have seen redrilled ones to match the TR PCD flange - obviously this has to be done very accurately and I can easily see this might not always be the case

Just some thoughts

Cheers Rich C-R

[ijonsson]

23 hours ago, John Morrison said:

I'm thinking this is drivetrain, try the neutral trick, and get back to us.

John.

He phoned me yesterday evening, and said it didn't help engaging neutral while vibrating. Now we will try to get hold of a set of brake drums and maybe drop the diff.

[ijonsson]

17 hours ago, Mike Herlihy said:

Bit of an odd one but had this on my own car, went on for years. Tried a friend's wheels and tyres, new propshaft, new standard driveshafts, new standard hubs, CV driveshafts as a last resort. Eventually traced to the output flange on the overdrive. It had obviously been dropped at some point and bent the flange. It was only obvious when a dial gauge was set up and used to check the runout. Fitted a replacement flange and all was fine. 

Maybe, we will end up there as well.  We are thinking of checking the balance of the propshaft even as the vibrations were there before the change of propshaft.

[ijonsson]

12 hours ago, rcreweread said:

Mike - that's a very good point, but the same could just as well apply to the other 3 output flanges in the drive line ie input and output flanges on the diff, and I suppose it would also be worth checking the trueness of the rear hub flanges.

One other thought - the gearbox output flange looks the same as the saloon ones but the PCD is very slightly different - I have seen redrilled ones to match the TR PCD flange - obviously this has to be done very accurately and I can easily see this might not always be the case

Just some thoughts

Cheers Rich C-R

OK, so adding "check flanges" to the list. Driveshafts and hubs are new (less than 1000 miles) CV-joint shafts from Limora/SC-parts.

[Z320]

Hi Inge,

for me it seems everything was changed with the hope of getting rid the vibrations,

but sorry me, without knowing the reason for them.

What not has been mentioned by you is the track and angle of the trailing arms?

I remember „a decade“ ago driving rear a club mate on a absolutely straight road

and the rear wheels of the 4A IRS had obviously not the same track and direction like the front wheels.

Because the hole car drove straight forward but „cross“ to the road and the rear „rolled“.

I told him but he did not worry. Well, he was not car sensitive.

The car had also other problems and I ask myself: how is it possible to drive years with multiple problems?

Ciao, Marco 

Edited September 3 by Z320

[ijonsson]

23 hours ago, Z320 said:

Hi Inge,

for me it seems everything was changed with the hope of getting rid the vibrations,

but sorry me, without knowing the reason for them.

What not has been mentioned by you is the track and angle of the trailing arms?

I remember „a decade“ ago driving rear a club mate on a absolutely straight road

and the rear wheels of the 4A IRS had obviously not the same track and direction like the front wheels.

Because the hole car drove straight forward but „cross“ to the road and the rear „rolled“.

I told him but he did not worry. Well, he was not car sensitive.

The car had also other problems and I ask myself: how is it possible to drive years with multiple problems?

Ciao, Marco 

Another thing to check, thanks. And, some have TOO sensitive bottoms and ears to drive vintage cars

[keith1948]

Hi Inge

Maybe you have excessive play in the wheel bearings. If the problem was at the front I would have expected you to feel the vibration through the steering wheel.  Do you have access to a rolling road?

Keith

[ijonsson]

3 hours ago, keith1948 said:

Hi Inge

Maybe you have excessive play in the wheel bearings. If the problem was at the front I would have expected you to feel the vibration through the steering wheel.  Do you have access to a rolling road?

Keith

Pretty new bearings in the front, and we checked the play several times since. As mentioned earlier the drive shafts are also new (CV-joints), including the hubs. We are pretty far away from nearest rolling road, but I can see how that would help.

[roy53]

Was this there before all the changes ?

Was it the same with both sets of wheels ?

                  "             "              half shafts ?

                   "              "           propshafts ?

[Z320]

8 hours ago, ijonsson said:

Another thing to check, thanks. And, some have TOO sensitive bottoms and ears to drive vintage cars

Indeed being less sensitive could help

(btw I‘m the guy who angled the diff of his 4A IRS different to get a better z-orinentation…)

Edited September 4 by Z320

[ijonsson]

14 hours ago, roy53 said:

Was this there before all the changes ?

Was it the same with both sets of wheels ?

                  "             "              half shafts ?

                   "              "           propshafts ?

As I recall, I think it got a bit better after fitting the CV-joint drive shafts.

[keith1948]

Hello again Inge

Maybe you could check the balance of the wheels yourself by doing something along the lines of this video

https://www.youtube.com/watch?v=dZp__T4KKuA

This would be only a rough guide but might indicate where the problem is. Maybe you could also bolt the brake drums onto the rear wheels and try to see what the balance was then. Of course the rear wheels could be positioned in one of 4 positions relative to the brake drums so a bit of experimenting. 

Also just an idea but if the brake drums were the problem what would happen if you swapped them left to right and right to left? They would now rotate in opposite direction to before and any unbalance would be on opposite sides of car.

Obviously you would need to have things balanced properly later but just trying to suggest some DIY ways of maybe identifying where the unbalance is. My feeling is that some part of the prop shaft, drive shafts, wheels, brake drums etc of rotating parts is out of balance. The symptoms are very like unbalanced wheels that I have had on cars before. However you have tried various wheels so maybe not that. It has to be something you have not touched yet.

Keith

Edited September 5 by keith1948

[ijonsson]

2 hours ago, keith1948 said:

Hello again Inge

Maybe you could check the balance of the wheels yourself by doing something along the lines of this video

https://www.youtube.com/watch?v=dZp__T4KKuA

This would be only a rough guide but might indicate where the problem is. Maybe you could also bolt the brake drums onto the rear wheels and try to see what the balance was then. Of course the rear wheels could be positioned in one of 4 positions relative to the brake drums so a bit of experimenting. 

Also just an idea but if the brake drums were the problem what would happen if you swapped them left to right and right to left? They would now rotate in opposite direction to before and any unbalance would be on opposite sides of car.

Obviously you would need to have things balanced properly later but just trying to suggest some DIY ways of maybe identifying where the unbalance is. My feeling is that some part of the prop shaft, drive shafts, wheels, brake drums etc of rotating parts is out of balance. The symptoms are very like unbalanced wheels that I have had on cars before. However you have tried various wheels so maybe not that. It has to be something you have not touched yet.

Keith

We did some work today, Took out the propshaft and checked the in and out flanges on OD and Diff, axial throw about 0,05 mm on both, so I don't think any of these are to blame. Balanced the Propshaft on a couple of horizontal edges (with the UJ:s fixed in straight position), it tended to stay in same position so we put a jubilee clamp opposite direction and it seemed to balance better. I had a couple of rear brake drums left over from my TR2, so we fitted those on the TR6. Hadn't time to test, exhaust still on the floor. Maybe we cant finish and test on Sunday.

[Topoff]

Could a rear hub/bearing cause something like this?  Just a thought.