Knocking/wurbling noise when braking severe chatter/bucking when backing up Getrag

[chevjerico]

Hey guys new member and new diesel guy, but life long hot rodder, drag racer, and backyard wrench. Needing to gain much needed basic diesel knowledge. I picked up a really clean 93 2WD, 5 speed, Getrag, club cab that was loved by the previous owner and hopped up a bit. Anyway that's my intro.

My current issue is that I hear a knocking noise coming from under the floor pan rear of cab when braking and coming to a stop. I bought a carrier bearing because I noticed the driveshaft moves around a bunch in the rubber mount and figured this couldn't be good. Maybe that's the way it is? I don't know. Something else I have that may be related is bucking/shutter when taking off in second gear, and is severe in reverse. Have to be careful, ease the clutch out slowly and rev the engine higher then normal when going in reverse.

I'm getting started later this afternoon. If you guys have any other ideas please post.

Thanks!

 

[JGrefenstette]

welcome to the family. the bucking when engaging the clutch sounds like broken springs in the clutch disc. mine did the same. could also be a combination of glazed clutch disc or hard spots on the flywheel. i know broken damper springs in the clutch discs is the number one cause of that symptom on 15.5" double disc clutches in road tractors. as for the knocking during deceleration, what are you doing when you hear the noise? coasting in neutral clutch engaged? coasting in neutral with clutch disengaged? in a particular gear while decelerating with transmission driving the engine (do you hear the noise under deceleration in all gears or just one?) or are you in a particular gear clutch disengaged coasting? when ever the back lash is reversed in direction in rear end gears, transmission gears, etc. you can often hear sounds of bad bearings or gear wear, that arent audible when the lash in the opposite direction. narrowing down those few scenarios will greatly help pinpointing a culprit. hope this helps. -jimmy

 

[B.G. Smith]

Welcome to the forums. The center support bearing (carrier bearing) may be the culprit. Could also cause some shudder in take off and reverse. Also look at the engine mounts while you are under there. bg

 

[JGrefenstette]

good call bg, could be worn engine or transmission mounts. i tried to solve my bucking issue with new polyurethane transmission mounts and new engine mounts (poly ones wernt available at the time). actually made the problem worse because it snugged everything up so the shudder of the clutch disc was more obvious. worn mounts make them selves known through the shift tower usually, if your gear stick is lopping side to side when you engage the clutch, there you have it. the carrier bearing should be tight in the rubber bushing, if the bearing is worn out that could sure cause some clunking, possibly during decel. i doubt it would cause the bucking at take off however. i had a freightliner at work a few weeks ago where the rubber and bearing were completely gone and the shaft was just spinning in the mount strap, and it made an awful racket but i didnt feel any difference at take off. and a kenworth did the exact same think this past friday, lots of noise but still able to pull 80k lbs down the road.

 

[RWherley]

Those, 2wd trans mounts, are junk and don't last very long I went through 3 of them before I changed to 4wd.

 

[S.Morris]

Check the middle Ujoint in the rear shaft

 

[chevjerico]

Thanks for the welcome guys, heard about this site from another diesel head I met at the races.

Didn't get to it yesterday. Figured I'd work on the knocking first, and then address the bucking. I hear it when coming to a stop with brakes on. Doesn't matter what gear I'm in or if I'm in neutral. Thought it might be something rolling around in my tool box, but it was still there after I unloaded it. It's a random knock under the floor pan louder and more frequent on bumpy roads or when braking.

 

[Bob Beauchaine]

There was a recall about this problem back in '93 when I bought my truck. Check the carrier and see if there is a 1/2" plate between the bearing plate where it mounts to the truck. They also added an angled shim to the rear springs. The were angled shims added to the rear springs to improve drive line angle. This helped some but did not totally solve this problem.

Bob

 

[chevjerico]

Thanks Bob, I'll take a look. I still haven't replaced the bearing yet. It's been too dang hot in Sacramento and I'm going to a Steve Miller concert this weekend.

Are you talking about both problems?

Does your truck still do this?

 

[chevjerico]

I do the see the plate between bearing and mount. I'm not sure if I see the wedge or not. I see a bracket on top of the axle tube that the leaf are resting on but no angle. There is also a spacer between the top most leaf and the rest of the leaf still no angle. Unless they are slight.

Does anyone know the service bulletin number for this, or the factory verbage used to describe it?

 

[Bob Beauchaine]

My truck does not have a back up shudder but does have a slight shudder but only once in awhile. Keep in mind that I am running NV4500HD and not a G360.

Bob