J type overdrive !

[Tonyw]

Is it possible to change the front bearing (prop end) without removing the whole gearbox and overdrive?

I have a slight vibration on the transmission and have now changed the drive shafts and hubs for Classic Driving development units, had the prop rebalanced and a gearbox rebuild. I have also replaced the bearings in the diff. This has all made a big difference but at times there is a slight vibration and as I had a faulty CV prop shaft fitted, that vibrated the car to bits (not literally), I suspect that it could now be down to the overdrive front bearing. The vibration is far better than it was and is now slight on deceleration.

Any input greatly received

Tony

[Guest]

On the J type nigh on impossible to get lots of play. Never seen.

The whole thing is much better done than the A type which required shims.
The D type used on the GT6 and Spitfire used to have problems with end float and horrible vibrations but again they use selective shims.

Check the quill shaft.
It's quite common for the bearing housing to get wear in the bore and this allows the little bearing to float around enough to have that effect. It's why I keep good s/h quill shaft housings....

The props are very long in the Stag /2.5pi and not very good.

[Tonyw]

Thanks for the reply.

I have changed the bearing in the quill shaft and the diff bearings. I have also had the prop balanced, but as I said I did fit a prop that was very badly out of balance and this is why I am wondering if it has damaged the bearing in the O/D.

Tony

[Guest]

Very unlikely.
It's more likely the bore of the quill shaft housing has been damaged so it's no longer really tight.

I used to have this problem on my fast 2000pi, which used to cruise all day at 110mph.
It's really a design weakness.
There's no other solution then but to change the whole darn quill shaft housing assy.
They don't last forever.

[Tonyw]

Ok thanks, I have a spare unit so I may strengthen that and fit it to see it it cures the issue.

Tony

[mike@thenook]

Hi Tony,

ive been plagued with vibration problems which have always sounded and felt like they come from the prop.
ive changed diff, quill shaft bearing and the entire housing, new lined prop built to original design and balanced, subframe mounts, clutch, flywheel, engine mounts and probably some other bits.
Oh yes, different wheels an tyres, all balanced - none of this has made any difference.
The out of balance only really comes in at 70 though and I still think it's down to the prop - down the plug hole is right about the length of the props and I'm not entirely sure the rubber lining does anything for balance, new or old.
I also tried runnning it with the drive shafts disconnected some whil back it it was still there.

So, I'm going to try the circlip method when I can face it and see if I can eliminate it that way.

Could be you have the same problem......?

[Guest]

If you have a rubber lined prop, FORGET IT!
They never worked on those cars, it's too long, too much flex and too much torque.
They always had to be slung out on the 2.5pi.

The rubber filled prop was a known issue on the 2.5pi.
Don't forget the cops had special engines, lots of extra equipment (and passengers!), and thrashed the daylights out of them.
They loved those pursuit cars because they went so well, and were sick when they got given 2600SD1 to replace them.

Why they changed it for the Stag and later pi, when the 2000 Mk1 as far as I know didn't beats me!

All the decent OD props for 2000-2500pi had to be made solid+sliding spline or they vibrated, and even then...spline wear OUCH!
The only solution I eventually found was to find a NOS spline and take it in to have it case hardened before making it into a "competition prop". That fixed it for good.

It's interesting to compare the strengths and weaknesses of the 2 Coventry based IRS systems. On a Jaguar the differential pinion is NOT on the centre line of the car, the crank is, so the prop has to compensate.
The post E type cars used subframes front AND rear, with dual wishbone susp.

Think about it, on the STAG, the crank is on the centre line of the car, so the only way they could make the pinion of the axle central is by offsetting the case and fitting 2 different length output shafts.
That was ingenious, but some of the weight of the diff is offset to the propshaft centre line.
The front suspension is not attached to a subframe, but to the body like the E type, while the rear is.

That on a Triumph, + a lot of the rubber suspended bits of engine, drivetrain and rear suspension is an invitation to all kinds of supplementary vibrations and misalignments (you'll find the amount of vibration varies with the loading of the entire rear end drivetrain, going through fast yumps and bumps!).

I just took it as one of the quirky fun features of those cars, - together with the entire rear drive train & subframe system loading up, then going "woink" and jumping when you took corners really fast. You just get used to it, and anticipate it just before a corner apex!

I have the same basic prop system on the Jaguar, -a part rubber filled prop, but the diameter is larger.
They have both a jurid coupling on the front of the diff pinion AND a bearing support for the rear part of the prop, AND most importantly it's proper dual wishbone suspension mounted on a proper subframe assembly with the heavy diff as a stressed member.

Under maximum load the rubber does induce some vibes, but you hardly notice it, hence why I moved back to the old pre 1988 solid prop for the race car, without rubber and without jurid coupling. That's the way to make a quiet drivetrain.

Despite the Jaguar and Triumph IRS dating back to 1961-3, (OH YES it is 55 years old next year!), Triumph did the 2000 on the cheap for 80bhp max, to get rid of the Vanguard cart sprung solid axle, while Jaguar made a race car dual wishbone IRS with disk brakes to handle easily 300-400bhp.
(Dolomite & TR7 reverted to the Vanguard system without the cart springs! eek!)

While a Jaguar E has no anti squat geometry it does give perfect alignment under load and in cornering. (the only weak bit being the V block system for quietening & the nightmare handbrake).

The Triumph system has not only NO anti squat, but variable toe, constant misalignment in the corners,variable aligment under load in the body, causing power train & torque misalignments AND change of track to boot.
All bad, which is why I guess the Dolomite & TR7 with their "50s design" rear end are more advanced! huh!

Some expression on the lines of "pigs", "purses" and "silk" come to mind.

[mike@thenook]

Interesting stuff and significant in that Peter at LD now only lists solid props for the Manual cars as has Monarch for years - could be the way to go..

Cheers!

[Andrew S]

Mike I had a solid prop made but didn't cure my problem I had it totally re balanced last rear too after fitting 2 new u/js so don't waste any more money unless you are sure

[Guest]

Are you sure the UJs are perfectly in line??
Just saying....

[mike@thenook]

Yep...

[Guest]

Then apart from sticking a camera under the car & making a video as it goes along and actually finding out what is going on there isn't much to do....apart from taking the prop to a different balancing company.

Can recommend Andy at Bassett, cos there isn't much he can't get spot on.