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Triumph TR6 - poly or rubber diff. bushings

My son and I want to change the rear diff. bushings that are no good on our '70. My question is, should we replace them with stock rubber or go to the poly type of bushings. Are there any pros or cons, any do and don'ts. I like to hear from both sides.
RJ Jio

Go with the polly. There is less movement (twist) of the dif. This helps save the dif brackets.

BUT!!! the first thing you need to do is check out the condition of your dif brackets. Back in '70 they had not added the stiffening/support braces to the brackets. The most common one for frailure was the front right one. You must full check all 4 brackets for cracks and weld in the reinforcement plates if not already done.
I have a template for the plates if you need it.

Rick Crawford

Actually Rick, there is some theory that the poly might hasten the demise of said brackets. Quite a few people are going back to stiffer rubber compound.

Not heard that one Don. I have the poly and I do not baby my 6. Don, I think you might mean the "softer" rubber compound.
In any event, RJ should check his brackets. Also the front suspension has stiffening gussets that can be added to very early TRs.
I think the problem with the dif and front suspension was resolved in manufacturing from '72 on.

Any other comments on the poly vs rubber?
Rick Crawford

I have the poly "blocks". They are actually solid chunks of plastic. If I had it to do again I would go with flexible ploy or firm rubber. The solid mounts stiffen the ride for certain, however they do telegraph a lot of diff whine. I believe the diff mount should have some give.
Steve C.
Steve Crosby

See Rick, Steve's with me!

I put in poly 5 years ago..the rubber ones looked crappy but when I removed them they were fine inside..even tho' I lube'd the poly's in the last year the fronts creak and groan when I hit a dip in the road etc.. when approaching a stop sign etc.
I'm going to pull the fronts out next winter, re-lube them and hope it solves it.
I never noticed any difference in ride or handling when I made the switch

Charlie B.

OK, so where can I get the firm rubber mounts? I din't want to get the standard rubber if they make a firmer set.
RJ Jio

I think it is TRF kit #711

That was RFK 711.

Looks like it has a new # now. I don't follow TRF that much anymore so I can't give you the new #.
Call them

Just a comment on poly and rubber.

Both are measured for hardness using a measurement called a SHORE RATING.

Rubber is about 75 or so depending on the mix.
Polyurethane can range from around 50 well up into the hundreds with other extremes available on special order.

Most poly makers use a colour coding to group their products with black being the softest at around 80 and white being the hardest at 400 + and other colours falling in between.

One plus with poly is it is not normally affected by road debris , UV , heat and so on but coating rubber with "rubber" grease will help protect it as well.
Rub it in using gloves until it takes no more and then install the bushing as normal. Then coat the bushing after it is installed to form a barrier.

Poly bushings should be lubed on installation with whatever is supplied by the maker.

Peter Thomas

This thread was discussed between 08/06/2009 and 21/06/2009

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