What's it For

[PaulR]

Hi All

I seem to have a large lump of iron attached to the rear of my gearbox (see photo). It looks like it should be there but what does it do and can I remove it?

The car has overdrive if this makes any difference.

Thanks

Paul

[stuart]

Hi All

I seem to have a large lump of iron attached to the rear of my gearbox (see photo). It looks like it should be there but what does it do and can I remove it?

The car has overdrive if this makes any difference.

Thanks

Paul

Its a damper and sometimes make a difference and sometimes doesnt. No-one has come up with a definitive answer yet

Stuart.

[Ade-TR4]

It's to dampen vibrations. Genious bit of engineering..."I know, we'll hang a f*****g great lump of lead off the gearbox; that'll do the trick!"

 

Remove, discard and forget! (or leave it and lug it around)

 

Cheers

Adey

[TR 2100]

I seem to have a large lump of iron attached to the rear of my gearbox (see photo).

 

Remove it and put it in a safe place.

Everyone else throws theirs away so before too long, they will become

a rare but essential item for collectors and concours mechants!

 

AlanR

Edited June 17, 2009 by TR 2100

[Smokey]

Leave it on. It reduces the vibration from the gearbox, which is essentially the vibration from a 2.2 liter 4 cylinder without balance shafts. You don't need it on the 6 cylinder, but I just remounted my damper when I replaced the rear oil seal on the overdrive, and there is a noticeable drop in grearbox rattle. It has some effect, and is totally harmless.

[RogerH]

I have theory !

Triumph were quite mean with their money but had very clever design chaps. They wouldn't waste money on a useless lump of iron if they could get away without it.

 

Roger

[RAHTR4]

Hi All

I seem to have a large lump of iron attached to the rear of my gearbox (see photo). It looks like it should be there but what does it do and can I remove it?

The car has overdrive if this makes any difference.

Thanks

Paul

 

Paul,

 

This rather crude set up was introduced in 1963 to reduce vibrations between 2700 and 3000 revs.

 

As Roger says, Triumph never spent money if they did not have to, so it has to be a part worth leaving on the car.

 

If you send me a PM with your e-mail I can send you a PDF copy of the Triumph Service sheet which introduced the fitting and shows more detail.

 

Regards, Richard

[TR 2100]

Triumph were quite mean with their money but had very clever design chaps.

They wouldn't waste money on a useless lump of iron if they could get away without it.

 

That is true, although current TR owners are somewhat sceptical about the true effect.

 

There were three different devices to try to cure the problem of general resonance

through the 2700~3000 rpm rev range.

 

The initial 'fix' was a spring and ball bearing in the base of the gear change lever.

They are a sod to fit, especially with the parts now available (spring too long)

and whilst being re-fitted, have often ended up on the workshop floor, never to

be found again.

 

Then there was an anti-vibration strap that was fitted between the gearbox extension

and the rear engine mounting.

 

The last 'fix' was the weight around the gearbox extension.

 

If you have all three fitted, that's about as much as you can do. From then on,

it's a matter of accepting the vibration/resonance, typically at 2700~3000 rpm.

 

Always assuming your gearbox is not in need of a rebuild.

 

AlanR

Edited June 18, 2009 by TR 2100

[Ade-TR4]

Richard,

 

any chance of posting the PDF on here for us all to look at?

 

Cheers!

Adey

[Smokey]

In my experience with my latest TR4, all three devices mentioned by AlanR have a positive effect in reducing vibration. When I installed the overdrive on this car, I thought the extra weight of the overdrive would be sufficient to act as a damper, but I still had a significant rattle. When I re-installed the reinforcing strap on the side, there was a noticeable drop in gearbox rattle on acceleration, and the large rear counterweight improved it further.

 

These are all band-aid fixes for the real problem: a four cylinder engine is inherently unbalanced, and at 2.2 liters, you're reaching the limits of tolerable vibration. That's why the Porsche 968 3 litre four cylinder had to have the Mitsubishi-patented counter-rotating balance shafts to be an acceptable engine in a street car. That's also why the same TR4 gearbox in the TR5 and TR6 does not have the reinforcing strap or the counterweight - the 2.5 liter 6 cylinder is inherently balanced as a design, and does not create the vibration in the gearbox. After all, the gearbox is actually the rear engine mount. On Alfa Romeos, you can feel the increase in vibration from the 1300 to the 1750, and they reached their limit of tolerable vibration at 2 liters. The TR4 strap and counterweihgt were a lot cheaper than balance shafts - which had not been invented yet anyway.

[Alec Pringle]

Hi Smokey,

 

a gentle correction.

 

The Mitsubishi patents referred to matters of detail, not of principle.

 

To their credit Colt (as they were then known in the UK) were at pains to give credit where it was due when they introduced their new engine range to the UK in the 70s.

 

Frederick Lanchester pioneered contra rotating balance shafts in 1904 . . . .

 

Cheers,

 

Alec

[Smokey]

Hi Alec, my apologies to Frederick - I should have know better. But that means that the Ferguson tractor engine could have used balance shafts instead of all the anti-vibration band-aids .

[RAHTR4]

As requested, below I hope - are copies of the original Triumph Service sheet and drawing.

 

Regards, Richard

 

 

[stuart]

As requested, below I hope - are copies of the original Triumph Service sheet and drawing.

 

Regards, Richard

 

 

Blimey that was generous of Triumph to allow 3 1/2 hrs to fit it!

Stuart.

[Ade-TR4]

Thanks Richard,

 

The extra steady bar seems to be absent from most installations!

 

Cheers

Adey

[Smokey]

Thanks, Richard. I had never seen that horizontal connecting strap, and may make one up just for fun the next time I have my gearbox cover off.

[TR 2100]

Blimey that was generous of Triumph to allow 3 1/2 hrs to fit it!

Stuart.

 

I think the factory allowance for removing/refitting the gearbox tunnel

was 1½ hours, so two hours more to fit this contraption does seem a lot.

 

AlanR

[stuart]

I think the factory allowance for removing/refitting the gearbox tunnel

was 1½ hours, so two hours more to fit this contraption does seem a lot.

 

AlanR

Perhaps they had a long walk to the stores

Stuart.

[Smokey]

You do have to remove and replace the driveshaft - eight nyloc nuts- plus the output drive flange on the overdrive or gearbox, in order to install the counterweight. The drive flange needs to be held by some sort of bolted bar, because it requires 100 foot pounds to tighten, plus the original castellated nut required a cotter pin. So there are a lot of small details to look after in the installation of that counterweight.

[stuart]

You do have to remove and replace the driveshaft - eight nyloc nuts- plus the output drive flange on the overdrive or gearbox, in order to install the counterweight. The drive flange needs to be held by some sort of bolted bar, because it requires 100 foot pounds to tighten, plus the original castellated nut required a cotter pin. So there are a lot of small details to look after in the installation of that counterweight.

You dont need to remove the drive shaft as the strap around the box carrying the weight is split and can be opened up and then bent back and bolted up.

Stuart.

[Smokey]

Hi Stuart, you're probably right, but I didn't try bending that strap - it's heavy 1/8" steel. It would take a lot of force to bend it enough to get around the driveshaft and the output flange, and then you'd have to bend it back again to the correct curvature to fit the gearbox extension. If the strap were split and bolted on both sides, it would be easy. But someone being paid 3 1/2 hours and with more skill (and strenght) than I have might have done that back in 1963 .

[stuart]

someone being paid 3 1/2 hours and with more skill (and strenght) than I have might have done that back in 1963 .

You bet they would have!

Stuart

[PaulAnderson]

You dont need to remove the drive shaft as the strap around the box carrying the weight is split and can be opened up and then bent back and bolted up.

Stuart.

 

 

Quite right I took mine off a couple of days ago in preparatio of work tonight, and after both removing the gearbox and refitting it back in again tonight, the last job I did before packing in for the night was refitting the counterweight / blob. It took about three minutes, largely spent aligning the various bolts, including bending / squeezing the strap to get the bolt back in.

 

Paul

[TR 2100]

Interesting Service Information sheet from Richard.

 

I have a few of these, ex-USA which would probably be different to

the UK sheets in some respects anyway, but there is no mention of

this damper in the 1962 or 1963 records. (OK - I do have a handful

missing)

I wonder if they were fitted to USA models? Illogical to not fit them,

but equally illogical to have no mention of them.

 

Also, interesting that the sheet is dated May 1963 yet there is a reference to

the damper being fitted from approx. CT 18000.

CT18000 corresponds to a manufacture date of November/December 1962

from what I have been able to work out.

May 1963 would be about CT12000.

 

AlanR

Edited June 20, 2009 by TR 2100

[RogerH]

I had to remove iron lump last month in order to shorten the bolt that holds the lump to the strap - it was hitting the Phoenix big bore exhaust pipe that runs under the G/B.

Took about 2 minutes to remove - pinch bolt removed, strap opened up to slide off G/B.

Took about 2 minutes to shorten the bolt.

 

Took about 1 minute to tighten the pinch bolt, but about 10 minutes to find a piece of studding to draw the strap together in order to clamp with mole grips and then insert pinch bolt. Job doen - result!!

 

 

As Smokey points out the strap is quite sturdy and closing it by hand is not really on. A short length of studding to draw the strap together, hold in place with mole grips, remove studding, insert pinch bolt - Hey presto!

 

Roger