great i am about to put in a 80. i am going to use a 2500hd crossmember. i hope mine doesnt start that.

 

All my angle look (by eye) straight. even if they were off quite a bit the dual cargan u-joints should fix it. Thats why I believe something is bent. I has the truck lowered djm 4/6 and the carrier bearing relocation mod. I got a flat tire and had to run home (500+miles) with two different size rear tires. One being stock height 30.05 and the other 27.7. I started to notice it after I had the blown tire replaced and installed. IT way of not been related but that is when I noticed it. Since then the truck has has all the stock suspension reinstalled and the carrier bearing bracked mod removed. I hate ghost problems. I don't mide fixing stuff as long as you know what is wrong, but by now i am so lost on this that when you take it to a dealer, they have no clue and just start throwing parts (and lot of $$$$) at it and it really doesn't help. Like I said the truck is too nice to get rid of, it's paid off, and I'd really like it to ride like it did from the factory.

 

I hear ya!

 

Did you check your axle runout... Maybe you axle is bent? Not sure, you just said it started after you ran the truck with 2 different size tires... maybe something happened during that.

 

mine has always has it between 40 and 45 and then 68 to 73 mph . doesnt matter what rims or tires i have on either

 

my dad had pretty bad shakin on his truck, he had just gotten new tires on it so he took them back and they had to rebalance them and now they are fine. perhaps it is all in the rubber?

 

i got the tires from discount with their free rotate and balance. I have had them balances about 300 times. Got my moneys worth i would say. The member that said it mayu be a bent axle may be on to something. another note. when i had my 245/40/20 ons (9.65 wide, 3.86side wall height, and 27.7 overall height) the shaking was ALOT worse. Less sidewall to absorb the shake.

I need to go to a salvage yard. Get all new front arms and steering rack(as one member suggested) then move out back and get a 4l80 and crossmember, and rear axle, then get a custom driveshaft made. Is there anything else that i could need to replace after all that?

 

The pinion bearing is in the rearend itself and the pinion yoke is attatched to the pinion in the rear end.It sounds to me like just the driveshaft was rebuilt.

 

i had the guy at the driveshaft shop drain some of the rear end oil to see if there was metal in it. IF the bearing was to go out i probably would have some shavings in the rearend oil.

 

I know on mine I have a little bit of a downward pinion angle after some 2" drop shackles. I'm going to try that, then if that fails, I don't have a clue what to try. I guess next will be checking welds on the crossmember and new tires.

Does anyone think that maybe a bad tranny mount or motor mounts could cause it?