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Back of truck shake
Hi all I’ve looked at this forum for a while and now joined. I have a 91 w350 manual trans 4x4. Single rear wheels. It has a Dana 70 with 4:10s I bought the truck a few years ago. From day 1 it has always had this shake that comes from the back. It starts to shake around 52 mph and continues up through 75 mph. I changed the tires. Have had 5 tire balanceing 1 being a road force balance ,installed new u joints changed brake drums 2 times, changed wheel bearings inner and outer, took out the axels and rotated them against a piece of cardboard. Removed the back drive shaft and it still shakes Have moved tires and rims front to back with no difference, checked rims on a tire balancer for bent and run out. The shock bushings are tight. The brake drums use a hub with studs. Is there any way to check balance on the brake drums? What else can I check to cure this problem Any advice is appreciated. Thanks |
Have a good look at the drums and see if they have weights or what looks like a broken weld if it has lost a weight. They are balanced in the beginning and will only go out if they lose a weight.
Next check the spring bushes but m y bet would be on the shocks need replacing. I know you have changed tires around but have you jacked it up and checked the run-out with the tires mounted to the hubs? Not familiar with these trucks, are the wheels located with the nuts or hub centres? Cheers Steve |
Have somebody drive behind you at the speed it starts shaking, they might be able to see what components are doing the shaking. I had a K10 that would shake bad at close to those speeds, but it was a broken band in the tire, the tire would violently wobble, but you couldnt see it from inside the truck.You have already eliminated that possiblity though.
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Thank you for checking my help add. I bought the truck with a broken trans. I had all new brakes including the drums installed while a garage removed the trans. The garage test drove the truck and told me The truck had square tires. I had the garage install new tires. Still shook. I have been to several garages for tire balance the last was called a Road Force Balence. I inspected the drums and found no balance weights. I ordered and installed new drums , the new drums had no balance weight either. I have not checked tire runout on the truck Thats a good idea for I have always checked run out on the tire spin balance machine, checked for bent rims on the spin machine also they all turn true. I will try that next. Spring bushings another good idea, how do I check them? The rims are centered by the hubs and axels, the axels bolt to the end of the hubs. The brake shoes are 12x3 inches. The drum weighs about 35 to 45 pounds each. Can a garage spin balance brake drums? This shaking feels like a tire way out of balance. Again thank you for any help or ideas you may have |
Might have the frame checked, the previous owner may have broke the transmission by trying a four wheel burnout. A friend of mine bought a brand new (when they first came out) fourwheel drive dually with the V10. Someone told him he could smoke all six tires with the V10...........yeah, it did it,....... once.... twisted everything out of wack! He never could get it back right, and finally sold it!
On a side note, just thought of something, make sure the u joints are phased correctly, but then you said you totally removed the rear drive shaft, so if that was it, it should have gotten rid of the vibration. |
With new drums I doubt that is your problem.
With the spring bushes a bar between the chassis and spring eye should show any movement if there is wear. Still leaning towards shocks. Could try varying the tire pressures and see if it changes. Guess with the work done so far the wheel bearings have been checked for play. Had a vibration around 60-65, found the cause when the front right tire threw the complete tread off, Tad messy. Cheers Steve |
Thank you for all your help I will try the tire run out on the truck and will also check the spring bushings. I changed inner and outer wheel bearings last year but no difference. I just installed new trans mounts but still no difference. After checking the first 2 then I will look at the shocks, maybe there is dead spots in them. I am also thinking of another set of tires since they are starting to look worn, not from any problem just mileage. When I find the problem I’ll post it here. Again thanks for your help |
I have a 01 Ford dually and have always had some vibration in the back end at highway speed. After trying everything else lowering the tire pressure to 45 psi was the only thing that ever helped, also with 500 lbs of feed bags on the back end the vibes are not noticeable at all.
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Hello. Thank you for your reply. I tried lowering the pressure from 80 down to 55 It didn’t make any difference but maybe I didn’t go low enough. With the truck fully loaded with green firewood not thrown in but stacked, oak and maple it still shook This is an 8 foot bed with single rear wheels I am not sure of the weight but it was pretty heavy. 2 days ago I found a shop that specializes in Dana 40,60,80 axels and differentials. One idea he had was if the truck sat for a while maybe the clutch plates inside the diff slid out of center causing an imbalance, or the diff bearings could be worn witch would also feel like a tire balance problem. With the diesel engin you can’t hear any thing on the highway except the diesel. Since finding this shop I’m thinking of making an appointment for an evaluation Again thank you |
Forest Service wood permits estimate Green Oak to be approximately 3000 lb. The exact amount listed in my door jamb of my 91.5 D 250. Thats a powerfull shake. Is the shake vertical , side to side ? Does the shake gets stronger with speed? Or just changing frequency corresponding to the changing speed? Could it be a pinion bearings alowing the drive line to move out of balance? Bad bushings on my 91.5 D250 they make the back and feel like a Cadillac squishy air suspension side to side or a low tire not so much shake. In the wind tunnel the rear of the truck moved side to side 2-3" @80mph air speed . tightened the bolts down that helped , but she still swings her hips in the corners . There 3 sizes used on out trucks Summit only had 2 listed , I had to order off measurements.
ride in the back and isolate which side or center? best of luck. |
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