Intermittant thumping sound at speed, getting worse 91 RT4WD
markymayhem
Band Wagon
Hey guys I hope someone has an idea of what's going on, I'm stumped!
I have a 1991 RT4WD wagon. I just got it a few months ago with 118k miles on it, now at about 125k. It's an automatic tranny.
About a week ago I noticed a thump or shimmy at speed on the highway, as if I had a bump in a tire, or needed the wheels balanced.
At first it was very minimal and I didn't pay much attention. Then it became worse, so I began to try and diagnose. I knew right away it wasn't simply an issue of balance, because it is an intermittant issue. Anyway, here is where I am at now:
Once the car has been driven a while, this thumping begins. It doesn't happen in neutral if the engine is revved.
After a cewrtian ammount of time on the highway, around 55 mph+, a vicious shimmy or thumping begins, as if there was a flat tire almost. As soon as I lift my foor from the gas, it goes away. So at speed, with foor off the gas, no problem. This leads me to think it's not a front end issue.
Anyway, once the issue starts, it used to come and go, now it just starts thumping and it's damn hard to keep up to 55 mph without feeling like the car is gonmna fall apart. ANY acceleration rpoduces this thump thump thump. Foot off the gas, it goes away.
When going from a dead stop, I can accelerate fine, no thumping at all all the way up. The shift point seems to be around 3200 RPM, no thumping at all. but at speed, when I accelerate from the 2200k or so idle up to even as little as 2500 rpm, the thumping sound appears.
And just yesterday, after a long drive, the thumping begain to happen at slower speeds, say 25mph on up. I stopped, turned the car off for a minute, started up and c ontinued at 30mph or so with much less of an issue. After a few hours on a job, I left at 40-45mph and had no issues all the way home.
I'm stumpped, please help!
-Mark
I have a 1991 RT4WD wagon. I just got it a few months ago with 118k miles on it, now at about 125k. It's an automatic tranny.
About a week ago I noticed a thump or shimmy at speed on the highway, as if I had a bump in a tire, or needed the wheels balanced.
At first it was very minimal and I didn't pay much attention. Then it became worse, so I began to try and diagnose. I knew right away it wasn't simply an issue of balance, because it is an intermittant issue. Anyway, here is where I am at now:
Once the car has been driven a while, this thumping begins. It doesn't happen in neutral if the engine is revved.
After a cewrtian ammount of time on the highway, around 55 mph+, a vicious shimmy or thumping begins, as if there was a flat tire almost. As soon as I lift my foor from the gas, it goes away. So at speed, with foor off the gas, no problem. This leads me to think it's not a front end issue.
Anyway, once the issue starts, it used to come and go, now it just starts thumping and it's damn hard to keep up to 55 mph without feeling like the car is gonmna fall apart. ANY acceleration rpoduces this thump thump thump. Foot off the gas, it goes away.
When going from a dead stop, I can accelerate fine, no thumping at all all the way up. The shift point seems to be around 3200 RPM, no thumping at all. but at speed, when I accelerate from the 2200k or so idle up to even as little as 2500 rpm, the thumping sound appears.
And just yesterday, after a long drive, the thumping begain to happen at slower speeds, say 25mph on up. I stopped, turned the car off for a minute, started up and c ontinued at 30mph or so with much less of an issue. After a few hours on a job, I left at 40-45mph and had no issues all the way home.
I'm stumpped, please help!
-Mark
Comments
Could the 4wd have been engaging when it shouldn't? Or maybe the viscous coupler isn't too viscous any more?
-m
And I picked up the car with a set of 4 'new' 2 yr old Goodyears with 90+% on them so I don't think that's it
The carrier bearings or support bearings going bad can make noise and vibrations. And at higher speeds, you notice them.
I just thought it was weird that letting off the gas made the noise go away, even though I'd still be traveling the same direction, speed etc.
Welcome to the world of RWD..
So I had the car in for alternator to the local honda/toyota indie repair shop. The guy didn't know anything about the switch thing to disable 4WD on the side of the tranny... but I asked him to take a look at the driveshaft and ujoints etc while he had it up on the lift. He said he couldn't see any issues with them,...
And the driveshaft and bearings shouldn't have any torque on them on the highway anyway, should they?