Motor Mounts: Effects on Transmission Shifting??

Nov 23, 2003 2 Replies

Well, I'm starting to think that the reason my transmission bangs into



2nd gear, especially under high RPMs and torque, as well as bangs into Reverse, especially when the engine is Hot, is not because of the tranny itself, but because of worn Motor/Engine Mounts.

My questions are:


1) Do worn Motor Mounts generally effect how a transmission operates?


2) Does Heat causes worn Mounts to get worse? In other words, I notice that the "banging" shifts get worse as the engine gets hotter. If the engine is only at 50 degrees in the morning, it's not very noticable, but as the engine reaches 200 degrees, the "banging/clunking" is getting out-of-hand.



I know that the Mounts in my car are hydraulic and are filled with fluid, so I thought maybe Heat would be an enemy, especially once they go bad.



The car is a 1990 Grand Prix w/3.1 MPFI engine and 4T60 transmission. I had the tranny mount replaced with a brand-new OE one about 2.5 years ago, so I doubt it's bad already. I also have had to replace the so-called "Torque Struts" or "Dog Bones" like 3 times. Once, a Brand-New "Dog Bone" actually broke right in half after only 2 days of use!! Obviously there was far too much strain on them. But, problem is, I can't remember if I just had them replace it with a New one, or had them replace the actual lower Hydraulic engine Mounts??? I don't think I had them replaced...



Is there anyway I can check the mounts myself??



THANKS!:)


You can check the motor mounts by opening the hood and watching the engine as you put it in drive and reverse while power braking (left foot on brake, right foot on gas). You'll see the engine rotate some while you give the engine some gas. A little bit of rotation is acceptable but you should be able to see the engine rocking back and forth. It should rock the same amount forward as it does in reverse. If one way is more than the other, you can suspect a bad mount. This is an alternative to visual inpection.

-Bruce

I had a beretta with a 4T60 which after a tune-up started banging as you describe. The 4T60 is a vaccum operated automatic transmission. Make sure there are no vaccum leaks going into it. The main vaccum line goes into the side/top of the transmission into an opening that looks like a canister. I hope this helps.

- JR

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required