Just seeing who has used rubber lower mounts over poly mounts. Some people have been telling me that I am going to have extreme stress on the tranny and cradle with this setup and others say that the rubber mounts can't hold up to the torque of the 3800. Which way is the best way to go? I already ordered the 3 poly lower mounts and the 1 poly front mount. Just curious to know who is using poly and who is using rubber and what problems people have ran into. Let me know. btw I am using a 5spd.
Maroon 1987 GT 5 spd: 2.8L Ferrari Red 1988 Formula 5 spd: 3.4L
I started out with rubber mounts on my 3800 SC with a 5 speed Getrag. I then installed WCF poly mounts. I really got a lot of engine vibration and jerking around when lugging the engine. The WCF mounts also raised the engine 3/4 inches. When I installed the intercooler I needed that 3/4 clearance back. I removed the poly and reinstalled the stock rubber mounts. I like them much better and the car feels more civilized. Even though I now have more engine power the rubber is holding up fine.
I had rubber, then I put my own steel hard mounts, and I like it. It does do the base idle shimmy on the dash a bit, but its still a comfertable ride with no vibration from anywhere else. I like the tight feeling, and havent noticed any frame distortion or cracking. I did notice the effort for burnouts was reduced 10 fold, but thats a good thing, also the bumpsteer and overall handling seemed to better with the hard mount no lateral movement setup.
I learned also, if you have ANY viberation.. YOUR FLYWHEEL ISNT RIGHT! My 3800 sounds and feels like it isnt running, thats how smooth it runs.
I've rode in StansGT and I must say he is right! You can't even tell the car is running. If you have your flywheel balanced and it is installed right you won't feel a thing. His car sounds and feels like a Caddy while at a stand still, but just wait for the gas lol.
------------------ "88" 3800 SC V6 Coupe "84" 4Cyl coupe parts car sponsered by = Car Quest
Posts: 13419 From: Where you least expect me Registered: Jun 2000
I installed a 3.8 S/C Auto, using the ACE kit with rubber mounts. They flex so much that the right side inner CV joint would hit the cradle. (a real mess when the boot gets knocked off). I installed a link between the cradle and the rear of the engine to prevent that from happening. A few years ago, I installed a 5.0 TPI V-8 in my 88. Solid mount to the cradle and of course the 88 cradle has no rubber mounts to the chassis. No vibration at all. I have considered solid mounts, just haven't done it yet.
I think we need to distinquish between 84-87 and 88 due to the cradle bushings. If you have rubber (or better yet poly) cradle bushings, then poly or solid engine mounts are fine. It's when you have solid cradle bushings that the motor mounts start becoming more important. The folks that consider the Fiero a sports car and like for it to handle good and drive in a "spirited" manner will forgive a little drivetrain vibration. Those folks that like comfort and use the car as a daily driver might prefer the rubber mounts. Personally, I have a couple other everyday vehicles, so my Fiero is a playtoy, thus I don't mind having a very firm solid ride. I'd probably go with the poly, but that's entirely up to you.
I use GM rubber and I've never had a problem with sagging or flexing (excessively). I have run into that problem with AM mounts (many from India, not that they can't make a good part) so I just spend the money on the better mounts and replace the rubber parts before they fall apart.
I do run poly cradle bushings, that seems to make a big difference in the Fiero. I'd like to try solid mounting the cradle sometime.
I'm certainly not forced to drive the car like grandpa with rubber mounts and bushings.
Aug 8th, 2003
Darth Fiero Member
Posts: 5888 From: Waterloo, Indiana Registered: Oct 2002
I am running all rubber and I certainly don't drive it like grandpa. Then again, I am using 75 Dodge truck mounts doubled up so I guess it is almost as hard as poly. for $4 a mount a zone why not double up? All 4 lower corners have mounts plus I am running a doggy bone center mounted in back.
------------------ 1987 Fiero Coupe 3800 Series II Intercooled Turbo 1987 Trans Am GTA 5.7L Superram 4L60-E 1985 Fiero SE 2.8 (soon to have an L36)
Im not sure about the time differnce with the hard mounts. I hard mounted everything on my swap, includeing the 87 cradle to the car.. which completely hard mounted to my frame. I still like,, I do however wonder about the hard shifts that may be harsh on the tranny internals. Its still alot of fun though