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Questions regarding function of vehicle rubber body mounts

Hi everyone,

I have some questions regarding the functioning of vehicle rubber body mounts in general, & specifically, rear cab mount bushings for Chevy K1500 series pickups having conventional two door cabs.

I have included a rapidshare link to a GIF image of an exploded view drawing for reference here...

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Referring to the drawing?

Part # 58 = Upper rear rubber cab mount bushing or cushion Part # 59 = Lower rear rubber cab mount bushing or cushion Part # 60 = Round steel retainer that goes under the lower rubber cab mount bushing Part # 61 = Cab mount bolt

You can see that the upper rubber cab mount bushing (58) sits on the top side of a steel support bracket that is integral with the vehicle frame. The upper rubber bushing is integral with a steel portion of the bushing. A round / oval shaped steel portion of the upper cab mount bushing extends downward from the underside of the bushing. The downwardly extending steel portion of the upper bushing fits through a hole in the frame support bracket.

The lower rubber cab mount (59) is installed under the frame support bracket, a round steel retainer (60) is positioned under the lower rubber bushing, and a cab mount bolt (61) is used to secure the system to the vehicle frame. The cab mount bolt is torqued to approximately 55 foot pounds.

Regarding the steel portion of the upper rubber bushing which extends down from the underside of the bushing, is this portion of the upper bushing supposed to ?bottom out? on the round steel retainer (60) which is installed under the lower bushing, when the cab mount bolt is torqued down ? Are the two steel components supposed to be in contact with each other when the bolt (61) is torqued down ?

I would appreciate any feedback.

Thanks John

Reply to
John2005
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Here is a link to the AMC Jeep CJ7 setup. They show the tubes sandwiched solidly pretty clearly on these mounts.

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Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Hi everyone,
Reply to
Mike Romain

Yes, the tube is supposed to be solidly clamped between the upper and lower washers. This gives the rubber bushings the designed preload.

Bob.

Reply to
Bob Flumere

Thanks for the the feedback guys,

Thanks for the picture Mike, however what is shown in the picture you uploaded appears to be a little different than the mount setup than what I have. I don't have a single tube that goes through both bushings, there is just a portion that extends down from the underside of the upper bushing, as shown in the drawing I uploaded. The lower bushing has no metal sleeve.

I wish I had a factory drawing for my specific vehicle or the K1500 series in general, showing a section view of the rear mount unit assembled.

Actually, after looking at this again, the rear lower mounts that I replaced look about the same thickness as the original front lower mounts. I had thought that after torquing the rear cab bolts down, the rear lower mounts were much thinner than the originals that I replaced.

John

Reply to
John2005

No, that is the end result, the anti-crush tube that is only 'connected' to the top bushing fits all the way through the bottom one that slides over it so the end result is two donuts compressed a fixed amount sandwiching the frame plate.

Here is an upside down photo of an extra new top frame mount I have as well as an old bottom bushing:

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That bottom bushing was under proper torque for 14 years, from 1986 to 2000.

Here is is fitted together, again upside down:

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Note the needed frame plate space left on the tube so when it is all together everything comes up tight.

Mike

John2005 wrote:

Reply to
Mike Romain

Hi Mike,

Thanks for taking the time to post those pictures for me, made everything clear. I appreciate you doing that.

I got to learn something about body mounts from this job (and the forums).

I could add some spacers or stacked washers inside the lower cab bushings so that the bottom retainer cup under the lower bushings pulls tight against the bottom of the sleeve on the upper bushings, but do I really need to do that as long as the lower bushings do not deteriorate too bad ?

As it is now, the lower retainer cup may, or may not, be pulled tight against the lower portion of the sleeve on the upper bushing. If it is, the lower retainer cup would have had to travel 1/2" further than it would normally, due to the two 1/4" thick support plates I added to the system. If the lower retainer cup is not pulled tight, I think it must be very close.

Thanks again, John

Reply to
John2005

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