Question about solid dogbone engine mount. (Page 3/3)
Blacktree JUL 06, 01:50 PM
It's not uncommon for Dukes to destroy motor mounts, as well. The usage is just as much a factor as the engine itself, if not more so.
Kevin87FieroGT JUL 06, 10:00 PM
Issue I’ve seen with two 2.8L (‘86 & ‘87) was the mushy OEM rubber mounts. Though I did put in poly dog bones, I replaced the engine and trans mounts with OEM style rubber mounts. The engines seem to be very secure and tight with the fresh mounts. The poly bone does transmit some vibration, but it’s minor and before you know it you don’t even notice it anymore. After 7 yrs with one of the cars new mounts there appears to be no abnormal wear with the rubber mounts, or poly dog bone.

Not sure why the factory rubber mounts were so mushy. On removal there was no oil on them just basic road crud ( prob oil based crud). Neither car was over 50,000 when I replaced the mounts. Fresh mounts do make the car feel tight though, well worth doing, and easy.
Jcbigbie SEP 11, 12:53 PM
Food for thought.

Sport bikes(from the factory) have solid motor mounts. The 4 cyn engine is bolted directly to an aluminum frame. Redline at 16,000 rpm. Only rubber is the tire and a cushion in the wheel between the sprocket and the wheel itself.

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88 gt
5 speed, Fidanza aluminum flywheel
2.8 V6, 1.6 roller rockers
Leather interior

cebix SEP 11, 02:37 PM
I've posted it a few times but my experience with the dogbone on a '85 2.5 auto is this:

Replaced the bushings on my original one since they were shot with prothane red poly. Drove around with that for quite a few years but the vibration in D at idle was teeth removing.

Decided to finally ditch it for a new rubber one and the difference was night and day. Didn't notice any real torque steer issues. Just the vibration went away so yeah. No poly there for me. I do have poly in the suspension all around though and the cradle bushings are poly for quite some years now. No squeaks, no worn bushings so far.
cvxjet SEP 11, 02:47 PM
A) The original engine mounts were not that soft...I decided to replace mine in 2000 with "Genuine GM parts!" and the ACDelco mounts were so soft that I could twist the trany mounts so that the tab was hitting the surround...The originals (With 130,000 miles and 16 years on them) were much stiffer. I found later that the Anchor brand replacements were much stiffer- more like stock (But the metal is thinner)

B) On my 85 SE w/3.4 F-body long block and 88 rear cradle, I swapped in poly on ONE side of my dogbone- left the other end rubber; limits movement but almost stock vibration isolation.

[This message has been edited by cvxjet (edited 09-11-2020).]

DimeMachine SEP 11, 11:31 PM
I had a poly dog bone in my 3800 Fiero for about 3 days. Couldn't believe how much Noise/Harshness and Vibration it introduced. For a drag car - sure. For a somewhat daily driven car, I would go crazy. My 2 cents.

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84/87 NB, 3800SC, E-85, VS Cam, 2.8 Pulley, 4T65E-HD, HP Tuners, AEM Wideband, Regal GS Gauges, S-10 Brake Booster. 1/4 mile -11.85 at 114mph

Frenchrafe SEP 12, 04:16 AM
Yeah, going poly or solid shakes the whole car, especially at lower engine speeds. Not for a daily driver!
If you trackday the car then having less drivetrain mouvement helps alot with handling.
For the torque at wheels question, I would say that it doesn't change that much. It's just how quick the energy is applied to moving the car forward. With the added risk of breaking/shearing a component!
Look how drag cars have soft(ish) suspension and how their tyres crease up on launch. All that in order not to loose grip. They apply torque progresively.

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"Turbo Slug" - '87 Fiero GT. 3800 turbo. Sticky tyres. Driven hard!
https://www.youtube.com/cha...1wZvWQlkYxTjivW_0XNg

[This message has been edited by Frenchrafe (edited 09-12-2020).]