Wife tells me that her 2008 GMC Yukon XL with 120k miles shudders when in reverse. Of course, it only happened a couple of times before she told me about it.

Just finished my checks. Car does shudder when the transmission is in reverse. Shudder goes away or is substantially reduced in drive. I only tested it for 20 feet.

Check transmission fluid while cold. Dipstick shows full with no burning or blackened cherry juice. Checked the transmission fuse and it is fine. Used a flashlight to look around the front drive train and do not see anything that appears broken.

What am I missing? What should I be checking? I think it is the transmission.

I hope to drop it off in the morning at a local shop as my transmission knowledge is limited.

What should I expect to hear?

Thanks.

Gig 'em

So you mean it shakes if you have it in reverse gear with your foot on the brake (i.e. not moving?) or is it when its moving?

Is it based more on physical speed or engine speed?

1agswitchin4lanes said:

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So you mean it shakes if you have it in reverse gear with your foot on the brake (i.e. not moving?) or is it when its moving?

Is it based more on physical speed or engine speed?

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It shakes as soon as it goes into reverse. Not based on physical speed at all.

Troy91 said:

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1agswitchin4lanes said:

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So you mean it shakes if you have it in reverse gear with your foot on the brake (i.e. not moving?) or is it when its moving?

Is it based more on physical speed or engine speed?

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It shakes as soon as it goes into reverse. Not based on physical speed at all.

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Sounds like an engine issue more than a trans issue.

How are the plugs/wires/coils?

I replaced plugs, wires and coils at 110k.

Shop is saying that a caliper bolt backed out and the caliper is hitting the wheel.

That's what I get for taking my life into my own hands and doing my own brake job.

that sounds fishy.

what about the motor mounts?

That's pretty believable. Same exact symptoms when a family friend's Acura MDX had a caliper bolt back out.

Should use loctite on those bolts, at the very minimum, put some stank on them when installing.

I definitely should have used loctite. I did the brakes in the fall so that bolt has walked out for the last 6 months.

how does the caliper shake if the truck isn't moving though?

FIL's 09 had motor mounts crack and had the same issue.

Motor mounts.