I've posted about this before, I have some new info though. I'll describe the problem. At random, I'll start up my truck and this occurs. There is some type of resistance, I'll start driving, and get a pulsating, surging response. It seems to match the rotation of the wheels. Sometimes I will throw it in gear, and it will sit there, like the tires have a flat spot, and not move forward. I will give it a little gas, and it move, then do the dragging thing. This will happen for a short distance down the road until I get up to speed and can't feel it anymore (it's most noticable at low speed). I can feel the dragging speed up as I do and dissappear. Intersting part, if I drive 5 miles, or maybe even 1 mile, after this happens, and pull over, put in P and back in gear, it will not do it. It will idle forward. I was playing around in nuetral on slight grades today. If I pay close attention, even when it moves forward, I think it does this to a minimal\unnoticable degree. I have also noticed a slight sound when spinning one of the front wheels freely, like a rub at a certain spot on each rotation (pretty light) Brakes seem to be allright. Just changed tranny fluid, oil, new plugs, haven't seen problems in other areas. Engine is strong. I've gone from brakes to torque converter to transmission trying to figure out what this is, and I don't want to pay a shop hundreds to find out. Now I'm thinking it's the wheel bearings. How much would it cost to have the wheel bearings checked and possibly replaced? Any advice? Tests? This doesn't stop me from driving, it's just driving me nuts, and know it's something that needs to be taken care of. Someone has to have a better guess than I do on this.
'96 302

 

The cost to replace your wheel bearing yourself would be less than paying a shop for an hour of labor to check them for you.

How did you rule out the transmission as the possible cause of this?

 

does it happen right after you back up?

 

Well, I haven't ruled out the tranny completely. At first I was convinced it was the tranny because after the fluid change it didn't act up. But sure enough, a few days later, it did it again. I was screwing around today and found out some more. I started it up, and it was "surging" pretty badly, so I built up speed and threw it into nuetral while it was happening. It continued though the free roll. That's why I'm looking more toward wheel bearings. Another interesting point, it doesn't do it in reverse. Pop it in D, it sometimes acts up, throw it into reverse, it will idle backward at normal speed. This confuses me. Keep in mind it had been intermittent for months now, sometimes not happening for 2\3 of a tank. Seems to be getting more frequent recently.
The front wheels seem to be allright, I spun them around today, and they went multiple turns just being spun by hand will one pull, seemed smooth. How big of a job is switching bearings? I suppose it can't be a big deal in the back. I switched to manual hubs, so I think I know how the front would be. I'm a novice, mainly only have experience in tune up or bolt on stuff.

 

I'm guessing that you wouldn't be able to duplicate the behavior when spinning the wheels by hand because presumably you have it jacked off the ground and the load is removed from the wheels.

 

when it happens are you backing up first like out of your driveway?since it doesn't happen in reverse i would check the rear brakes.

 

Changing the bearings isn't difficult; it just involves disassembling the 4WD hubs, cleaning everything up, putting in new bearings and seals, and repacking with grease. However, if you're considering a bearing failure, you'll want to check out the condition of the races inside the hub and on the spindle to make sure that they aren't tapered, scored, etc. It shouldn't take you long to tear the hubs down and check everything out.

 

What kind of tires do you have? Since you describe it as a flat spot, bias ply tires will form a flat spot after sitting and as they warm up and rotate it goes away. It is common to put theses on 4x4's because they conform to trail obstacles better. I agree with the other gentleman though that rear brakes sound like a possibility as well since it does't happen in reverse. If you use your e-brake alot, then I would definitely check there.

 

I run 32x11.50 MT\R's. Maybe I'll try not using the e-brake and see if it stops. Wouldn't the bearings make noise? The e-brake would be one variable that changes every time I park. I think it's non-adjustable on mine though. Allright, thanks for the replies, I think it's definately drag on the rear wheels, and that's progress.