2000 I4 2WD Auto thumping, frequency increases with speed

[fastmk2]

Hello ExplorerForum message board,

I'm trying to diagnosis (and fix) my father-in-law's 2000 Ranger 2WD I4 automatic pickup.

I recently drove it (about 2 weeks ago); there's a thumping that started ~10 mph and increased with engine speed to the point that it was just a constant very noisy thrum. I thought it was coming from the front driver-side area of the car.

I (mis)diagnosed it as the worst failing front wheel bearing I'd ever heard... I was able to take a closer look at the vehicle was last night. I tore into the DS front wheel bearing... To my surprise, everything looked great. Apparently he'd had the front bearings done a while back (but forgot?). I replaced the bearings, races, and seal on the DS front anyhow and put everything back together. Drove it around my neighborhood and nothing has changed. Still the incessant thumping that increases with speed, noticeable at about 10 mph and getting really noisy by 30 mph... I didn't drive it any faster. Problem NOT solved.

Crawled back under it with the rear-end on stands, tried to rattle the driveshaft around but both of the U-joints seemed solid (and looked newer). There's fluid (and no leaks) in the rear differential that was replaced ~18 months ago when I replaced the outer bearings in the rear axle.

Put the truck in drive, had my brother-in-law depress the throttle to the point where we can hear the thumping and crawled back under the truck. I wasn't keen on putting my face near the drive shaft, but the sound seems like it's coming more from the front of the transmission rather than the rear. Do torque converters ever become unbalanced?

There's a leak from the rear main or transmission input area of the engine (I should have tried to figure out if the fluid was oil or transmission fluid, but I didn't).

Spent the morning searching google and this message board for similar problems, but have turned up nothing.

I won't get to mess with the truck until the next time he's down to visit, but would like to have a good solution to this problem.

So... Anyone ever experience something similar? Please let me know. Thanks!!!

 

[McCormack]

Does the thumping increase with engine speed, or with road speed?

 

[fastmk2]

I want to say it increases with road speed. It runs through gears (so the engine speed would decrease, right?) and yet the noise continues to increase.

 

[McCormack]

If the thumping increases with road speed then you can pretty much rule out the engine being the cause of the noise.

You say that it sounds like it's coming from the transmission area... if it were me I would first pull the rear wheels to make sure that nothing is amiss with the brakes or drums, and if I found nothing then I would take the truck to a trusted auto repair shop and give them a crack at diagnosing the problem.

I've heard far too many stories of folks having their transmissions rebuilt only to have them fail again, so if the tranny turns out to be bad, I would get a used one out of a salvage yard. A salvage yard trans is also cheaper than having an existing transmission rebuilt. Most yards offer a warranty on their engines and transmissions.

Some salvage yards will install transmissions and engines for a reasonable fee, and if I couldn't find a yard that did, I would call around to the local independent auto repair shops and get some prices for doing the job.

 

[fastmk2]

I'll take a good look at the rear end and go from there. If nothing, I'll definitely find a shop to check things out and diagnose.

Thanks for the tips/advise on a used transmission. I'll look for one as you've suggested if it is determined to be the culprit.

 

[McCormack]

Hope you get 'er solved.