Shake rattle and roll.............'86 MGM 5.0

[Toploader]

Question:
If I am on the highway at cruising speed and stomp the gas for the low gear downshift, the entire car shakes, and I mean shakes! ........till I ease off the gas.

Ok guys tell me the bad news;-)

[Brown_Muscle]

Does it shake before or after it shifts? Could be a motor mount, driveshaft out of balance. does it stop shaking when it up shifts again, or just gas related?

[gadget73]

does it actually downshift ? If not, sounds like low TV pressure. Check the bushing. Low pressure would also tend to upshift very early.

[friskyfrankie]

Hope you have the brass replacement grommet as opposed to the OEM junk (plastic) for the throttle linkage right under the TB. As stated, also check trany fluid level.

[Toploader]

Hope you have the brass replacement grommet as opposed to the OEM junk (plastic) for the throttle linkage right under the TB. As stated, also check trany fluid level.

There is no TB its an '86 5.0 EFI, I also added 2.5 qts of tranny fluid.

[Toploader]

does it actually downshift ? If not, sounds like low TV pressure. Check the bushing. Low pressure would also tend to upshift very early.

Yes it does downshift! Now that I topped off the trans, I will see this week when I take the car out from NYC to Long Island, pleanty of time to see how she reacts.

[Toploader]

Does it shake before or after it shifts? Could be a motor mount, driveshaft out of balance. does it stop shaking when it up shifts again, or just gas related?

Shakes just before it shifts,then smooths out.

[friskyfrankie]

Does not an '86 have the grommet I mentioned? If so (which I believe it does) then get the brass one and pin to replace it with. 2.5 qts of trany fluid is a lot. Are you sure it required that much? If you are sure, either someone serviced it low or you have a leak. Proper level will eliminate that issue as a problem (as long as no leaks are present). Let us know how it runs!

[DerekTheGreat]

There is no TB its an '86 5.0 EFI, I also added 2.5 qts of tranny fluid.

It indeed does, the TB (throttle body) is the thing where the throttle blade, IAC valve and all throttle linkage stuff lives. Does it have a misfire? When is the last time you peered under the skirt of the distributor cap or checked the plugs & wires?

[VicCrownVic]

It indeed does, the TB (throttle body) is the thing where the throttle blade, IAC valve and all throttle linkage stuff lives. Does it have a misfire? When is the last time you peered under the skirt of the distributor cap or checked the plugs & wires?

He means no TB grommet for the TV cable at the TB. '86 was the one year only setup that didn't use that junk bushing setup.

Lithdoc, when he was still here in MI, had his TV cable sticking on his '89 MGM, lubed it and was fine. Not sure exactly how or what he lubed though, think it was just the trans end of the linkage. Make sure your TV cable is moving freely.

[Toploader]

Does not an '86 have the grommet I mentioned? If so (which I believe it does) then get the brass one and pin to replace it with. 2.5 qts of trany fluid is a lot. Are you sure it required that much? If you are sure, either someone serviced it low or you have a leak. Proper level will eliminate that issue as a problem (as long as no leaks are present). Let us know how it runs!

When I get the car on the lift I will check the two fittings at the trans that comes from the radiator cooler tanks. The pan is dry. I have not checked the dipstick in two years;-(

[Toploader]

It indeed does, the TB (throttle body) is the thing where the throttle blade, IAC valve and all throttle linkage stuff lives. Does it have a misfire? When is the last time you peered under the skirt of the distributor cap or checked the plugs & wires?

My bad yes indeed it has a TB! Car never misfires, and when I stomp it the car does not miss or break up upon acceleration. Plugs are two years old, wires good.

[kishy]

I'm thinking misfire while in the higher gear which doesn't happen once in the lower gear (typical as high load at low rpm is where misfires happen most).

Getting these things to not do that is tricky in my experience. I cure it (and other things I can't stand about these cars) by adjusting the TV so high they're probably in danger of blowing seals. TecNickal recently drove my 85 and would surely vouch for it not driving like an AOD at all.

Check plug gap & condition, distributor rotor contact condition, and wire routing. If this is not a long-time symptom it is probably ignition stuff getting just slightly out of optimal condition.

[gadget73]

86 does NOT have a bushing. Not sure why I was thinking he had an 87. Not like it was in the title that I obviously read closely or anything.

[friskyfrankie]

Yeah, I couldn't remember if the 86 has the grommet or not. 87 does for sure but I guess the 86 does not?