Transmission mount advice.

Sub03

Well-Known Member
Joined
Apr 5, 2020
Messages
54
Reaction score
31
Location
Norway
Hi everyone.

After spending a year chasing a cyclic vibration noise in my '77 Aspen (5.2 magnum/a904) in the 1800-2000 rpm area, I discovered the problem was a little dent in the power steering pump pulley. Replaced pump pulley and crank pulley and the Aspen was smooth again.

Hoping to get rid of a slight driveline vibration in 35-45 mph and 75 mph++, I replaced U-joints and transmission mount on it yesterday.
The vibration issue is gone, but now I hear a mid range rpm noise through the floor. I'm sure the cheap (Westar) trans mount from Rockauto is the source of my problem. Engine running strong and smooth, no misfiring.

Googled the problem and found several Jeep forums stating aftermarket trans mount is crap with rubber being too hard, and OEM is the only way to go.
Comfort is my goal here, so I prefer rubber mounts and not poly.

Has any of you guys or girls any experience with this? What brand should I buy?
 

volare 1977

Member
Joined
Apr 29, 2021
Messages
14
Reaction score
1
Location
maryland
The last couple i bought were NOS mopar ones but they are getting hard to find and expensive when you do find them. The quality in the rubber nowadays is crap especially india and china so that doesn`t leave many choices.
 

Mikes5thAve

Well-Known Member
Joined
Mar 3, 2020
Messages
538
Reaction score
184
Location
Canada
Rubber still ages so the only real benefit to nos is the better metal bracket. The one I used was an anchor one and it wasn't made perfectly straight.
 

Aspen500

Well-Known Member
Joined
Feb 14, 2015
Messages
5,589
Reaction score
1,819
Location
Rib Mountain (Wausau) WI
After building my car, I had the cyclic resonant type of vibration also, around 45 mph and up. Tried this, that and the other thing with little to no change. Going by the vibration frequency, I knew it was related to the drivetrain. As a last ditch effort, I replaced the poly trans mount with a stock style I got at Carquest next door to work, they actually had it in stock(!), and,,,,,,,,,,,,vibration gone. When the stiff poly bushing transmitted normal driveline vibration to the body and the hertz of the vibration matched the resonant frequency of the body, it caused a very annoying resonance and vibration. Got to the point where I didn't even want to drive the car at more than city speeds.

IIRC, the mount was made in India but it's been in there almost 10 years and seems fine yet. Guess India crap is better than China crap, but not by much.
 

Sub03

Well-Known Member
Joined
Apr 5, 2020
Messages
54
Reaction score
31
Location
Norway
Thank you for responding guys.

After building my car, I had the cyclic resonant type of vibration also, around 45 mph and up.

Yeah, I saw your post in this thread from three years ago:
Unfortunately the thread died out without any conclusion from the thread starter.

My vibration is definitely rpm related and not prop shaft/wheels.

I found som mounts at Mancini racing and Summit racing. The prices being a bit higher makes me think they could be of better quality. But then again I don't know, and it's a pain and time consuming to order and ship to Norway if they are crap too...

So I was hoping someone who changed their tranny mount lately would chime in with what brand they used and if it turned out OK.
 

volare 1977

Member
Joined
Apr 29, 2021
Messages
14
Reaction score
1
Location
maryland
Theory sounds good but I never had any issues with any NOS rubber mounts I have used. I will take them over the junk out there nowadays. I buy them any time I see them at a decent price.
 

BudW

Moderator
Staff member
Joined
Mar 4, 2012
Messages
4,640
Reaction score
1,295
Location
Oklahoma City
Urethane (or Polyurethane) for engine/transmission mounts are only for racers.
For street use, only use rubber, or the noise/vibration will bug the dickens out of you.


Actually, for racing, I might consider the Left engine mount being Urethane (or solid), but leaving the Right side and transmission mounts rubber. The other two mounts will not lose any power transfer and will prevent breakage and reduce vibrations.
Either that or directly tie the engine to the chassis:
BB Motor Plate Ft.png

BB Trans Motor Plate.jpg


I wouldn't be surprised there is only one or two people manufacturing our (rubber) mounts - then companies putting their sticker on the box.

Rubber will go bad over time - but I think the high/low temperatures our cars see, as well as oil/coolant and other contaminates also does a number on it as well (oil will cause rubber to deteriorate pretty quick). I would not have any worry about using a new but old rubber mount.

The only thing that might make a transmission mount hard to find is some FMJ mounts have an extra (welded on) exhaust mounting bracket - which might finding the correct mount hard to find. About ten years ago (or so), I bought a few transmission mount inserts - so I could reuse my existing metal transmission mount frame:
Trans Mount Insert.png

I have yet to install an insert, but have heard from friends they can either be easy to install, or a royal pain (mainly getting the old metal shell removed). Now transmission mounts, in general, I have replaced a bunch of in my life - but some of the transmission mounts specific to a few FMJ's are getting hard to find.
BudW
 

Aspen500

Well-Known Member
Joined
Feb 14, 2015
Messages
5,589
Reaction score
1,819
Location
Rib Mountain (Wausau) WI
The spool mounts (technically insulators) on our cars have very little movement to begin with as compared to pancake mounts, provided they're in good condition. I'm talking both engine and trans. Even if the engine and trans internals were balanced to perfection, there's still a vibration caused by the firing pulses. One reason so many FWD (and even some RWD) cars with a 4 cyl vibrate so frigging bad at idle when in gear. Firing pulses equal the resonant frequency of the car, or steering column, or whatever and they vibrate something awful. If you look at the engine, it seems to be sitting almost still but inside the car you'd swear there's a 2 lb weight attached to the flex plate. Ford Focus comes to mind. Feels like sitting in a giant vibrator. No, I don't mean THAT kind of vibrator :)
 

Mikes5thAve

Well-Known Member
Joined
Mar 3, 2020
Messages
538
Reaction score
184
Location
Canada
Mine is anchor brand and like I said other then the sleeve through it being on a slight angle I've never had any problem with it.
 
Top