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K3500 Shaking Like Hell in Reverse

acm

acm

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Having some issues with my old K3500 (L29/4L80E). Has the tire balanced & rotated again today (seems it takes them at least 3 tries to get the balance close). Went to back it out of the parking break and the entire truck just shook.

Felt like something was caught in the wheel but there were no strange noises. Seemed ok going forward and only shook badly when backing up slowly? Motor and tranny mounts and the carrier bearing looked ok. Pulled the wheels off and everything looked normal.

Drove the truck home, nothing unusual. Decided to drive it a bit and it did fine until I had to back it up the driveway. It has a decent grade to it and the truck rev’d going up it. Was a bit worried it might not make it.

Next checked the trans fluid, it’s a bit low (middle of the cold range) As soon as the rain lets up, I’ll add some more fluid and see if it gets better but guessing than the trans is about done.

Never had a trans go out where it shook the vehicle like this. Hopefully it’s not a collection of problems.

Anything y’all can think of I missing or ideas of what to check next?



…and before I get all the missing pedal comments. This forker is staying with a slushbox!!!
 
When you said you pulled the wheels, did that include the brake drums?

Was curious if the parking brake is grabbing. Maybe push the p brake down a click and see if it still does it?
 
Tried messing with the parking break. Didn't make any difference.
Haven't pulled the drums yet but did rotate them by hand with the wheels off. Taking them off is a good idea though...been putting off rear breaks for awhile now.
 
Anything balanced in forward is balanced in reverse. The transmission could slip in reverse, but that typically comes with no compression braking in manual L (have you tried manually shifting to 1 to see if the engine RPM stays with vehicle speed?). As mentioned above, there are some things that can go wrong with the brakes that seem to be fine in forward. For discs, a missing caliper bolt can do that. For drums, there are a few issues that can let one end of the pad grab the drum in only one direction.
 
Check the rear pinion. When one bearing fails they will turn freely only in one direction.
 
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@Blue85 agreed balanced is balanced. It's all about moments around a center line. Don't think the tires/wheels have anything to do with the issue,
I need to pull the drums off a check them. Kinda hoping that they are worn enough nothing screwy going on but the brakes would be the easiest to fix and converting to rear disk wouldn't be all that bad.

@ChrisPerry Shit, hadn't thought of that but it makes sense. Now I'm hoping for something jacked up with the brakes.
Wouldn't you expect some noise?

Thanks for all the input.
 
Not always, doesn't take much to cause a vibration. Dodge 1/2 ton trucks used to have the pinion nut back off, those were always fun.
 
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ChrisPerry said:
Not always, doesn't take much to cause a vibration. Dodge 1/2 ton trucks used to have the pinion nut back off, those were always fun.
Click to expand...

The only thing I've changed recently is adding a pinion guard. Maybe the bolts backed off. Will check tomorrow.
Thx
 
ChrisPerry said:
You bolted it over the pinion not under it, right? lol
Click to expand...

Bolts??? The originals were too short but had some really bitchin duct tape...:dunno:

Seriously, checked all the bolts and obvious stuff without taking the drums off. Everything seems ok.
Leaning to a line pressure problem with the trans. Sounds like @jeff in co had a similar problem.

Got a 211k out of it, so not too bad. Time to visit @Greg Ducato.

Thanks for all the replies.
 
acm said:
Checked all the bolts and obvious stuff without taking the drums off. Everything seems ok.

Got a 211k out of it, so not too bad. Time to visit @Greg Ducato.
Click to expand...
You're going to tear into a trans project without even checking the brakes? You should also pull the driveshaft to check that pinion. Could still be the rear diff.

H20 Toie said:
Dude its super easy, dont back up :)
Click to expand...
I knew a lady who went 9 months with no reverse, just by careful planning. Having an uphill driveway probably helped, too.
 
Blue85 said:
You're going to tear into a trans project without even checking the brakes? You should also pull the driveshaft to check that pinion. Could still be the rear diff.
Click to expand...

Yes, but I've had it on jack stands with wheels off. Rotates fine in both directions. Even applied the parking breaks and rear is smooth. Also didn't see any goofy movements with the thing in drive or reverse...
Pinion is good. Paint marks still line up.
Trust me, an issue with the rear end wouldn't be tragic. I want 4.88's and a SAS.

Plus now it will not reverse at all. Just rev's. There's a line pressure issue in the trans.

H20 Toie said:
Dude its super easy, dont back up :)
Click to expand...
Funny you mention this. A buddy of mine has a rep for driving trucks with no reverse. He won't work on them till it stops. Stopped by today and asked if I was finally ready to sell him this one...
 
Take your axle off. Grind the perches off and weld them on the other side of the axle tube. Flip axle over so the driver side is now on the passenger side. Voila - now you have reverse! :D
 
No, flip the front axle because high-pinion fronts are cool. Twin stick the transfer case and use the front for reverse and rear for forward. Just don't engage both at the same time.
 
I've seen a truck that shuddered and shook in reverse bad,it turned out the u-bolts were so loose the pinion flipped upwards when you torqued on it in reverse,and the u-joint bound up.!..after it was taken apart to put new u-bolts on,the spring center bolt was broken on one rear spring and the perch on the axle tube was rotted where it was welded and was no longer holding it in place!..

Truck was towed into my friends shop with the explanation "Reverse going out--needs transmission"...but it worked fine one he fixed the perch and u-bolt and center bolt problems..
 
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