I have a 1998 gmc k1500 with a 6" lift. It has a wobble at 40mph.I have new tires,new pitman, and idler arm. I have new ball joints. and all the tie rod ends ane fine.

if this has a conventional front end(not front wheel drive) then there will be one on each outer tie rod end one on each inner tie rod end, both upper and lower ball joints on each side, idler arm and pitman arm. if its front wheel drive it will have a rack and pinion steering. there for there will be one on each outer tie rod end and one on each lower ball joint, if they have grease fittings. so conventional steering has 10 fittings total and rack and pinion has 4 total.

??? could be tie rod ends , idler arm , pitman arm , ball joints or gear box need to get it on a lift and see

The inner and outer tie rods are pretty self explanatory remove the nut from the knuckle. Whack the knuckle a couple times where the tie rod goes through and the tie rod will pop out. The inner will releas the same way. Get the sleeve whe you get the inner and outer tie rod. It will make life a lot easier. Assemble the new parts to the approximate same length as the parts you removed and install. The idler arm will be bolted to the frame and then have a ball and socket that will be removed in the same manner as the tie rod end. The pitman arm will require a puller to seperate it from the gear box. Sometimes you have to heat up the end that attaches to the gear box to get them to pop. Sometimes the gear box needs to be removed in order to get the puller on the pitman arm. Lower and upper ball joints are also very common on these. If they have not been done I would have them checked as well.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Best guess is worn steering tie rods first. it doesn't take much wear for wheel shake to occur in the 4wd versions. next would be other steering components- idler arm and pitman arm. next would be ball joints- these are probably already needing replacement due to 4wd and age.
Good luck

You could have a bad tie rod end, Idler arm, pitman arm, wheel bearing or ball joint. All of these will normally cause a vibration also. Check by jacking the front end one side at a time and moving the tire back and forth on front and back and in and out on top and bottom. Either watch or have someone else watch the steering assembly for movement and where it is. If there is no unusual movement, it is more than likely an alignment problem or tire problem.

Relay Rod Removal & Installation To Remove:

1. Raise and support the vehicle
2. Remove or disconnect the following:
   • Engine protection shield, if equipped
   • Steering damper from the relay rod, if equipped Note: Use the proper tool in order to separate all the tie rods and the ball joints.
     Steering components
     
     
   • Tie rod ends (F) (See: Tie Rod Ends)
   • Idler arm ball stud nut (J) and discard the nut (See: Idler Arm)
   • Pitman arm nut (H) and discard the nut (See: Pitman Arm) Remove the idler arm from the relay rod
     
     
   • Relay rod from the idler arm ball stud using the J24319-B or other suitable puller Remove relay rod from pitman arm ball stud
     
     
   • Relay rod from the pitman arm ball stud using the J24319-B or other suitable puller
   • Relay rod from the vehicle
3. Inspect the threads on the tie rod ends for damage
4. Inspect the ball stud threads for damage
5. Inspect the ball stud seals for excessive damage
6. Clean the threads on the ball studs

To Install:

1. Install or connect the following:
   • Relay rod to the vehicle
   • Relay rod to the pitman arm ball stud
   • Relay rod to the idler arm ball stud and make sure the seal is on the stud
   • New pitman arm prevailing torque nut
   • New idler arm prevailing torque nut and tighten the idler arm and pitman arm nuts; Torque to: 46 ft. lbs. (62 Nm)
   • Tie rod ends
   • Steering dampener to the relay rod, if equipped
   • Engine protection shield, if equipped
2. Lower the vehicle
3. Check the wheel alignment
4. Test drive the vehicle to confirm the repairs

YOU NEED TO CHECK TIE ROD END S AND WHEEL BEARING OR BALL JOINTS AND CONTROLL ARM BUSHING HOPE THIS HELPS LIFT TRUCK GRAB WHEEL AND LIGHTLY MOVE SIDE TO SIDE SEE IF YOU HAVE PLAY IN TIE RODS GRAB WHEEL TOP TO BOTTUM AND SEE IF WHEEL BEARING HAS PLAY OR SPIN THE WHEEL TO SEE IF YOU CAN HEAR GROONING NOISE FROM BEARING DOING THIS THINGS YOU MAY BE ABLE TO TELL IF ITS BALL JOINT TOO

you can usually find all the parts your needing parts and labor for tie rods, ball joints, control arms springs shocks idler arms pitman arms parts and labor will probably run you close to 1500 dollars probably lower.

tire pressure low,alignment jack up the front end and wobble the tires side to side the body lift would not effect this

Ball joints, idler arm, pitman arm and tie rod ends are all problems with these vehicles. If any of these parts are worn it can cause your problem and it cannot be properly aligned until the parts are replaced..