Hey everyone. I've had this really annoying rumbling problem for a while now. I have a '97 4runner, 4cyl, 5 speed, 148,XXX miles. I've had three toyota mechanics look at my truck, drive the truck, and diagnose the problem, but they obviously weren't right because the problem is still there:

If I drive 65 on the highway and put the truck in nuetral, it will make a faint grumble until the speed bleeds off to the area of 50-59mph. Between 50 to 60, there is a large vibrating rumble, which promptly stops after 50. It just stops rumbling. This also happens in other higher speeds, but putting it in nuetral highlights the worst of it. Sometimes, when the truck is in gear going down a hill and I give it just a LITTLE gas, I will also hear and feel the rumbling

Now for what I've done: (or what toyota has done)
-relaced rear U joint
-resurfaced rotors/new brakes,shoes, etc
-replaced entire rear differential
-rotated / balanced tires

What the heck else would make the truck rumble so much? The only thing I have left to consider is if the driveshaft is out of balance.
Any thouhts???? Nothing would sound wierd at this point.. Thanks in advance!!!

did you check the engine mount yet?

I haven't, but would that still be affected if the truck is in nuetral? Do you think the spinning driveshaft could be trying to move the motor around? I'll check first thing in the morning..

I had this happen on my 97 4x4 with 5 speed and v-6. I had to replace the drive shaft.... Had the original one reblanced twice, and even retubed!!! had to swap out with used one from junk yard and problem went away...

I had an expedition under my truck today. I checked everything, motor mounts are good, no wear on any U joints, front driveshaft looks fine.

I found a reputable driveshaft shop near me and made an appointment to get it balanced tomorow. That's honostly one of the last things I could think of.
Question: If I take off the rear driveshaft and use 4wheel drive, can the truck still drive semi normally? I don't need to take it off because the shop will, but I'm curious.

Do you have oil in the transfer case and tranny? Did you try putting it up on jack stands and running the wheels. I'd recheck for play in both diffs and fluid as well. My initial guess would be drive shaft or ring and pinion Esp with the decel symptom. Did they REALLY swap the dif? While you are down there, check the front CV's/Birfs and the Tulip joints. After that I'd start looking at bearings. If it is only making sound when you are moving, it's gotta be behind the tranny.

I know that they swapped the diffs for sure because the unit on my truck is a different color, and they showed me the old one. Oil in tranny, and I assumed transfer case, although I'll double check...I'm getting the driveshaft balanced tomorow, so hopefully I should know more after that.
Thank you for all your inputs, I will run through everything suggested! <img src="/forums/images/graemlins/cheers.gif" alt="" />

So they changed a dif that didn't need changing? Ouchy. FYI The front shaft doesn't spin in 2WD unless you have a Limited with the fulltime option.

<Edit> Ok I read things over and you have base 4cyl which will have the lever xfer.

No, the rear diff definitely needed changing. The bearings were shot and it wouldn't even let me coast on the highway without rumbling and 'locking' up every now and then (that was real fun).....it wasn't an e-locker, but you could have fooled anyone else, the rear diff was done with. The truck is definitely better with a new diff, but I'm looking to fix everything up before the fall. During school I'll have no time for any of this!

Just out of curiosity... How long have you had this truck? What did the previous owner do with it? I just got one of these with 200k on it and it seems dang near perfect. I mean under normal use I would not expect so much driveline wear and tear. I mean if a guy had fun wearing out his truck it would be worth it and all, I just wonder what it takes.