Urethane Vs. Polyurethane Vs. Polygraphite

My 73 Charger Rallye 340 CID 4 SPD still has the factory installed K member and torsion bar cross member isolators.

Energy Suspension has them in Polyurethane.
Prothane has them in Urethane.
PST has them in Polygraphite.

I am not considering solid mounts.

I have Polyurethane leaf spring isolators so I am leaning towards Energy Suspension Polyurethane.

I really would appreciate feedback on the 3 options above. I'm looking for the best quality. Cost is of no importance.

Suspension bushings are all versions of polyurethane compounds which are a fairly rigid compared with straight urethane which can have varying degrees of softness. I'm not away of anyone making soft urethane bushing. Polygraphite is a polyurethane that has graphite mixed into the compounds. The idea being that the graphite is self-lubricating and will avoid the squeaks that tend to come with using straight polyurethane.

The for frame and cross member isolators, I don't think the polygraphite version has any real advantage of regular polyurethane as they are not in a motion position that will constantly generate squeak potential. Once bolted down you should be fine.

I think whether they squeak or not has a lot to do with the suspension design too. I have had polygraphite and urethane in Diplomat Police cars in the entire front end and had no squeaking. Never found them to be too stiff either. Really not any noticeable difference to me. So I would probably recommend polygraphite so that if there was going to be any squeaking it might help with that and not require routine greasing. I also had PST's and was happy with them.

I know you mentioned you did not want solid mounts. I have to say, one of the best upgrades I did on my Diplomat Police cars were aluminum k-frame biscuits from firmfeel. So much better high speed handling and just handling overall, and no bad side effects whatsoever.

These come in rubber if you want that option. https://www.moparmall.com/1973-74-B-Body-Sub-Frame-Isolator-Set-p/801-528.htm

At one time Chrysler had a police kit to replace the bushings with Cast iron biscuits , I did that on my 79 300

One of the poly kits has an oval, steel insert; the other does not. I would buy the one with the insert. Check Rockauto for good prices.

EDIT - the Energy Suspension ones have the captured insert. If you look at the same set in red you can see it. Don't forget poly for the torsion crossmember, too.

I remember that kit. A NOS one popped up on ebay a year or so ago. Best upgrade ever!

We have done a butt lload of PST kits over the last 20 years. using Liberal amount of the special lube on install we haven't had a squeaker yet

I was searching for them to post the option on thread, but on eBay. Tipically FMMOPAR had them in $299 as far I recall. AMD also shows them on a similar price than Moparmall but out of stock. There is an ebay seller offering just the K member pieces thought.

This would be my option but not at that price. Saying that and per what has been said here, would go with urethane.

Is really the rubber way more expensive material than poly or urethane to be sold on THAT price comparing with poly/urethane?

how long, or how many miles has the longest install been used ?
just curious. i have CHS and probably couldn't hear a squeek unless it was 95 decibels or so..........

Well As I told I knew FMMOPAR had those, but weird is not with the T bar crossmember isolator too. I know they had it on $299 or so

K member isolators FMMOPAR

There is a crazy guy selling the full set on $377

https://www.ebay.com/itm/NEW-1973-1...y-Rubber-ISOLATOR-Mount-SET/363027089179

Thaaaats the one. Dunno why I couldn't find it earlier!!!!

I've got an old DC kit on my wagon.

Never understood how people say a solid K rides SOOOOOO much harsher, when, essentially all you've done is make it like a '72 / older. If there is indeed any added harshness, the tradeoff for better handling is worth it.

But, I digress.....

is the torsion bar cross member isolated on the later B bodies like the K member ?
my old mind forgets. if so, are there kits to mount it solid ?

Yes, the T-bar crossmember is isolated, so the car basically ends up with two crossmembers (the T-bars pass thru the first one).

Firm Feel makes solid mounts for the K and the crossmember.

Thank You !
i thought so, but wasn't sure. i need to eat a few bottles of those pills advertised on tv that makes your memory better........

Hence the reason why 73 and Lates T-Bars are longer than previous years and just aftermarket pieces are available, nothing from MP

Eggg zactly! People weren't bitching about a harsh ride back in the pre '73 cars.

To o/p: NOW is the time to get rid of the rubber K frame isolators! You won't regret it.

And that seller of the rubber ones is always super high priced. At least go polyurethane for better handling AND save money.

Thank you all for the responses. This has been quite the education.
In the old days one could have walked into a parts store and looked at the parts. Not any more!
Thanx again guys.