Motor mounts?

[efnfast]

I've noticed my shifter seems to lift noticeably when I drop the hammer on Bertha. Motor mounts?

[Ccmano]

Possibly or loose C frame (Beam) bolts at the trans or both...
H
:cheers:

[Young1]

I've noticed my shifter seems to lift noticeably when I drop the hammer on Bertha. Motor mounts?

C beam bolts. The C beam ties the trans to the differential and the torque lifts the tranny if they are loose. Others will comment I am sure.

[secondchance]

Steve,
I would check the C beam bolts first.

[efnfast]

I'll put it up on the lift and check it out. Anything special about tightening them?

[secondchance]

I'll put it up on the lift and check it out. Anything special about tightening them?

I believe fronts are 40 lb-ft and rears are 60. Do not over tighten. Could result in ovaling the housing relative to shaft.

It is possible to use torque wrench without removing the exhaust. I can't remember if I used "U"joint extension to get around the exhaust or crow feet open end. If using crow feet, I would stay a shade below 40 lb-ft since you will be eccentric relative to the extension.

[Dynomite]

You should install C4 Beam Plates from ZFdoc as described here ........Post 39 - C4 Beam Plates and Installation (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-2.html#post1581480716)

www.zfdoc.com

[Ccmano]

While the C Beam bolts are the most likely culprit and the ZFDoc beam plates the best solution (wouldn’t drive a C4 without them) don’t assume your engine mounts are good. They need to be inspected. 30yr old oil filled rubber right next to the exhaust manifolds is a bad combination. Every single C4 I’ve owned and many I’ve inspected have had at least a bad right mount if not both. If they are original, dollars to donuts at least one is bad.
H
:cheers:

[efnfast]

Thanks for all the input.
Bill C Beam plates have already been installed.
I'll check the motor mounts, Pete had the engine out last year, I would have thought he would have noticed.

[efnfast]

C Beam is not obviously loose, but I did not put a socket to them.
Motor mounts? Floor jack and 2x4 under the oil pan?

[Ccmano]

C Beam is not obviously loose, but I did not put a socket to them.
Motor mounts? Floor jack and 2x4 under the oil pan?

You’ll need a torque wrench to check C Beam bolts properly. I think someone posted the specs. For the motor mounts jack the front of the car properly from the frame rails and put jack stands under the frame corners where the frame juts in behind the wheel wells. The frame K-members have to be removed including the bottom nut to the motor mounts. That will give you access to the mounts but you have remove the heat shield covers that go around the mounts to see them properly. It’s one of those deals where it’s such a hassle to check them you might as well just replace them while you in there if they're original.
H
:cheers:

[efnfast]

I'll drop the exhaust and check the c beam first.
Are the motor mounts standard C4, available at Chevy, or the local parts supplier?

[Ccmano]

Motor mounts are common to the 92-96 LT1/LT4 cars. The L98 mounts are different. Rockauto is your best bet.
H
:cheers:

[Ccmano]

Here’s how mine looked although they did have 180k on them. Both broken. Funny enough on the last Z with only ~45k miles they look just as bad. It a function of age more than miles.
H
:cheers:

http://a67.tinypic.com/30uflg2.jpg

[XfireZ51]

Steve,

If u notice that the left side exhaust keeps moving around or loosening up, then I’d suspect right side motor mount. Have somebody rev motor and see how much it torques over.
My left side muffler mount kept loosening up and then I discovered(w Pete) that right hand MM was cracked. Now replaced. Not easily seen. U gotta look for it.