Vibration 1996 c1500

[TS6235]

I have a lowered 1996 c1500, short box, single cab truck. Vibration is between 55 and 62, feel it in the seat. The truck is lowered 5/7. I've replaced the u-joints, had the tires balanced (wheels were true) etc. I do see the driveshaft has what appears to be a lot of angle at the trans. I did shim the trans up and the vibration got worse. Ideas?

[killthewabbit]

You might try shimming the rearend to get a better pinion angle there.

[TS6235]

Originally Posted by killthewabbit

You might try shimming the rearend to get a better pinion angle there.

Thanks, i'll follow up when I shim the rear.

[Tom]

After a couple of years of owning my truck lowered I did a burnout one day off road onto an asphalt road. Something weird happened and I got massive axle hop, flat spotted a tire bad. When I changed tires, the virbration didn't go away. Fast foward 3[!!!]yrs. Several sets of tires, new control arm bushings and ball joints up front, shocks in the rear, u-joints, trans mount, driveshaft shortened to perfections and balanced perfectly, the rims+tires balanced at least 8 times, a trip to the GM dealership for diag, you name it I though I had done it.

Finally I figured the rims were bent. Took it to a guy to check, he said nope just all 4 tires are out of balance. He checked them for free, so I paid him to balance them just so he made something out of the deal. He used this fancy 'road force' balancer. My drive home was so smooth, so nice. Ecstatic didn't do justice to how I felt. Now I work in the industry, and road force is the only thing I'll let my fleet have used on them. 99.8% of the time you feel vibration, its wheel balance related.

[TS6235]

Originally Posted by Tom

After a couple of years of owning my truck lowered I did a burnout one day off road onto an asphalt road. Something weird happened and I got massive axle hop, flat spotted a tire bad. When I changed tires, the virbration didn't go away. Fast foward 3[!!!]yrs. Several sets of tires, new control arm bushings and ball joints up front, shocks in the rear, u-joints, trans mount, driveshaft shortened to perfections and balanced perfectly, the rims+tires balanced at least 8 times, a trip to the GM dealership for diag, you name it I though I had done it.

Finally I figured the rims were bent. Took it to a guy to check, he said nope just all 4 tires are out of balance. He checked them for free, so I paid him to balance them just so he made something out of the deal. He used this fancy 'road force' balancer. My drive home was so smooth, so nice. Ecstatic didn't do justice to how I felt. Now I work in the industry, and road force is the only thing I'll let my fleet have used on them. 99.8% of the time you feel vibration, its wheel balance related.

What typical tire shop carries the "road force" balancer?

[Blue97]

Originally Posted by TS6235

What typical tire shop carries the "road force" balancer?

this should help you locate one.
http://www.gsp9700.com/search/findgsp9700.cfm

I also have a vibration between 45-50 just like a slow bounce

[TS6235]

Originally Posted by Blue97

this should help you locate one.
http://www.gsp9700.com/search/findgsp9700.cfm

I also have a vibration between 45-50 just like a slow bounce

See a Firestone right by my house. Thanks

[TS6235]

Originally Posted by TS6235

I have a lowered 1996 c1500, short box, single cab truck. Vibration is between 55 and 62, feel it in the seat. The truck is lowered 5/7. I've replaced the u-joints, had the tires balanced (wheels were true) etc. I do see the driveshaft has what appears to be a lot of angle at the trans. I did shim the trans up and the vibration got worse. Ideas?

I changed the shocks, vibration got worse. Shocks stiffened the ride, they were for a lowered truck BTW. Put wheels and tires from the 72 on it, vibration still there. Shimmed the diff -4 degree shim, vibration still there. Seems if must be the diff, vibration is in the seat/floor between 52 and 62 or so.

Ideas?

[TS6235]

Originally Posted by TS6235

I changed the shocks, vibration got worse. Shocks stiffened the ride, they were for a lowered truck BTW. Put wheels and tires from the 72 on it, vibration still there. Shimmed the diff -4 degree shim, vibration still there. Seems if must be the diff, vibration is in the seat/floor between 52 and 62 or so.

Ideas?

I noticed tonight one brake drum has balance weights, the other side doesn't. Can't tell if it had them previously. I've had the truck 1.5 years and just getting to this issue. Could this be the issue?

[Boog]

Did you buy the truck this way or did this develope after you lowered it?

[TS6235]

Originally Posted by Boog

Did you buy the truck this way or did this develope after you lowered it?

Bought it this way. odd thing is it worse now that i've been messing with it.

[75ChevyGuy]

Does the truck have a 2 piece driveshaft? If so there is a shim that you are supposed to put underneath the carrier bearing. That could possibly cause the vibration if it isn't there.

[TS6235]

Originally Posted by 75ChevyGuy

Does the truck have a 2 piece driveshaft? If so there is a shim that you are supposed to put underneath the carrier bearing. That could possibly cause the vibration if it isn't there.

No, one piece driveshaft.

[Keith Seymore]

Originally Posted by TS6235

Bought it this way. odd thing is it worse now that i've been messing with it.

Well....if you can make it worse then you can fix it...



Seriously, that means your changes are affecting it somehow. Just take everything back to where you started and move the trans the other way.

K

[Keith Seymore]

Originally Posted by TS6235

I have a lowered 1996 c1500, short box, single cab truck. Vibration is between 55 and 62, feel it in the seat. The truck is lowered 5/7. I've replaced the u-joints, had the tires balanced (wheels were true) etc. I do see the driveshaft has what appears to be a lot of angle at the trans. I did shim the trans up and the vibration got worse. Ideas?

Normally if it's bad and then gets better as you go faster - it's driveline.

If it's bad and continues to get worse with speed - it's tire/wheel.

This is because the driveline on its own doesn't have enough mass to excite the whole truck. It needs the synergystic (multiplying) effect of a resonance. That means you feel the disturbance as you pass through the resonance period and then it dies down as you lose that multiplying effect.

Tires and wheels, on the other hand, are not so surgical. They are big and nasty and have enough mass to drive a disturbance once they start, building in intensity as fast as you want to go.

K

[TS6235]

Originally Posted by Keith Seymore

Normally if it's bad and then gets better as you go faster - it's driveline.

If it's bad and continues to get worse with speed - it's tire/wheel.

This is because the driveline on its own doesn't have enough mass to excite the whole truck. It needs the synergystic (multiplying) effect of a resonance. That means you feel the disturbance as you pass through the resonance period and then it dies down as you lose that multiplying effect.

Tires and wheels, on the other hand, are not so surgical. They are big and nasty and have enough mass to drive a disturbance once they start, building in intensity as fast as you want to go.

K

Funny, it's exactly back where I started. Just changed one thing at a time and put back if it didn't change.

Going to put a dial indicator on the axle flanges this weekend to see if maybe one of them is slightly bent. No noise associated with the vibration either. When the u-joints were changed the driveshaft was chucked up in a lathe and spun. They said it was fine.

Pinion bearing feels tight as there isn't any odd noises in the rear. I did feel last night on the freeway about 15 MPH an ossilation back and forth I haven't felt before.

[TS6235]

Originally Posted by TS6235

Funny, it's exactly back where I started. Just changed one thing at a time and put back if it didn't change.

Going to put a dial indicator on the axle flanges this weekend to see if maybe one of them is slightly bent. No noise associated with the vibration either. When the u-joints were changed the driveshaft was chucked up in a lathe and spun. They said it was fine.

Pinion bearing feels tight as there isn't any odd noises in the rear. I did feel last night on the freeway about 15 MPH an ossilation back and forth I haven't felt before.

Update,
Axle runout .004 each side, I replaced the bearings just because, replaced the brake drums as well, vibration is still the same. I also checked the driveshaft angles, -4 at slip yoke and + 5 at diff. I think i'm going to take the driveshaft and have it re-balanced. Not sure where else to go at this point.

[TS6235]

Well got the driveshaft back and in, vibration still there. Not sure where to go next?
The driveshaft place told me when I picked it up it wasn't my problem.

I did follow the truck at speed and could see the u-bolts on the rear springs bouncing when the vibration was present.

I'll try the Firestone store today, I'm skeptical thats it as i replaced the wheels and tires prior with a set I know doesn't shake and it was the same.

[TS6235]

Used a digital guage on the angles

trans -1.8
Driveshaft +1.6
Rear +2.0

I read I need atleast 1.0 operating angle. Is this my vibration?

[TS6235]

Just my luck, had Firestone rebalance the tires, They tell me " oh yeah they were off, it shakes worse than ever now. Hope there open today.

[TS6235]

Well I give up, shimmed the rear up and down, both ways makes the vibration worse. Shimed the trans up, got worse. Had Firestone balance all 4 tires/wheels. I can make it worse but can't make it go away. Odd thing is you can barely feel it when it's on jack stands. Tire and wheels made no difference. The vibration when on jack stands is barely noticeable no matter the changes made. I wondering if it's in the diff? It feels fine when your turn it? I did have the cover off when replacing the bearings and everything looked good.

[Blue97]

Man I feel your pain! After two lift kits, three sets of new tires, two sets of rims, countless alignments and balance with the last one having road force balanced and replacing EVERYTHING under the front end TWICE along with new u-joints / carrier bearing, shocks,removing lift blocks / adding lift blocks , replacing wheel bearings just because and I forget what else I have done in the last three years......

I still have a bounce between 40-50mph

I have a 80lb spare tire in the bed, i removed it just for shizz&giggles also I pumped up the tire pressure to the max aswell.

If this don't work the only thing I can think of is put it all back to stock and go from there........but that will have to wait for cooler days

[TS6235]

The things that's irritating the most is it's worse than when I first started trying to find it and has move up in MPH.

I might go after the tailshaft bushing next. I didn't notice a lot of play in it but who knows.

[old cool]

did you ever find out what was causing the vibration. I too have vibration at 30-40 range. I have addressed driveshaft, yoke, and ujoints. I have tried two diff sets of wheels and tires. Still there. Truck sets pretty close to stock.
Some have suggested motor mounts and/or trans mounts could be a concern.

My next fix is pinion seal and pinion bearing. I know there's a little slop there. I saw it when truck was up on jacks.

Is the engine, trans, drive shaft all in alignment? If any of these parts have been changed its something to consider.

Hope you solved you problem. Look forward to answer.