TR6 Help! TR6 Diff Mounts - poly or rubber?

[bunzil]

I read that the rear diff mounts need to be reinforced if poly mounts are used instead of rubber? This is supposedly because poly transmits more vibration and shock. Anyone have any opinion or experiance here? While I won't know until I look, last time I was up there my mounts were fine. Obviously if there is damage I'll fix 'em, if I don't need to should I stick with rubber mounts? The car does not see heavy use, especially on the drivetrain. Thanks.

 

[kodanja]

I beilive the rubber will wear out quicker, but I've heard the poly ones have a tendency to squeek...

 

[Andrew Mace]

It depends...at least with other suspension bushings, there are several "grades" (firmnesses) of poly. Just a guess, but I suspect that the "average" poly diff. bushing would be pretty comparable in firmness to the original-type rubber. Given what I've seen of so much current replacement rubber suspension bits, I imagine the poly ones will certainly last longer!

 

[TR6oldtimer]

The old adage 'If it ain't broke don't fix it' still applies. I got lots of miles and years on the original rubber before I replaced them. The reason was due to improper repair of a damaged frame mount. While I did go with poly but it was a coin toss decision. Some have said that replacement rubber mounts are softer then the original. Who knows.

Like I said, if the old ones are still in good shape so are you.

 

[ROADSTR6]

I went with poly when I was last under there to fix a broken diff mount. The poly bushings I got came from TRF and they don't squeak at all. I'm happy with them.

Dave

 

[bunzil]

I think you guys missed the question. I'll gladly put rubber back in, but I know poly will last indefinately so that's my first choice. But since my mounts have not been strengthened, will the firmness of poly transfer more impact to the mounts, where the softer rubber would absorb more? In short, is there a chance poly will put more strain on the mounts thereby potentially cracking them prematurely, where rubber might not? I ordered poly from Victoria and will check them against the old rubber on arrival. But I read just last night in the TR Improvement book that strengthening the mounts is "essential" if switching over to poly. This is the first I'd heard of it.

 

[martx-5]

[ QUOTE ]
... But since my mounts have not been strengthened, ...

[/ QUOTE ]

What are you waiting for?? It's not a matter of if the mounts will break, but when. I would think that it would be easier to box them in and strengthen them BEFORE they break. Then you can put in the poly bushings and not have to worry about it.

 

[DougF]

I have never heard anything about having to reinforce your frame to use poly bushings. I welded in plating on mine when the car was apart, that is really the only easy time to do it.
When purchasing the bushings, ask the salesperson if they know or if somebody there has heard of this being necessary.

 

[bunzil]

Good point. But I don't happen to have a spare welding kit hanging around. I've driven the car for 22 years, it seems hard to believe I'm going to start beating on it now.

 

[bunzil]

Further, I've never heard of needing the reinforcing for the mounts either, and I've been working on, reading and talking about these cars for years. But there it is on page 28 of the relatively newly published "How To Improve Triumph Tr-6" by Roger Williams: "If you plan to fit poly, it's essential that you not only fully box the diff pins but reinforce the top of all four pins across both diff bridges." Now I don't believe everything I read, and this sounds a bit extreme, but I thought I'd ask the Forum anyway if they have any experiance in this area.

 

[DougF]

I believe in his book, he may be addressing all of these modifications as a whole. If you are pumping 180 bhp. into that rear mount set-up, yes, you should reinforce the frame.
These frames were built to endure 150 bhp. Granted, steel will weaken over the years. But if you are using your car for sunny weekend tours and not weekend autocrosses, I can't imagine you will have problems.

 

[bunzil]

[ QUOTE ]
I believe in his book, he may be addressing all of these modifications as a whole. If you are pumping 180 bhp. into that rear mount set-up, yes, you should reinforce the frame.
These frames were built to endure 150 bhp. Granted, steel will weaken over the years. But if you are using your car for sunny weekend tours and not weekend autocrosses, I can't imagine you will have problems.

[/ QUOTE ]

That's a perfectly logical explanation. And a little common sense needs to prevail here. Thanks. I've noted over the years the desire to inject increasingly more technology into these cars, when they were reasonably reliable in the first place. It certainly pays to look back, examine the design intentions, and see how they suit our current needs. In my case, the diff mounts have not failed in 30 years, the car is clean, no rust, and has not been beaten. I'll install the poly mounts for longevity versus rubber for softness. Thanks again.

 

[Andrew Mace]

[ QUOTE ]
I think you guys missed the question....since my mounts have not been strengthened, will the firmness of poly transfer more impact to the mounts, where the softer rubber would absorb more? In short, is there a chance poly will put more strain on the mounts thereby potentially cracking them prematurely, where rubber might not?...

[/ QUOTE ]I thought I did sort of address that. Actually, I don't know for sure if there are different "grades of hardness" of poly bushings for the diff. mounts, but there certainly are for other suspension mounts. Ultimately, I would ask before buying them from anyone (and hope they can give a knowledgeable answer).