Vibration as high speed (sometimes)
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New Member
Joined: Nov 2025
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Vibration as high speed (sometimes)
98 GMC JIMMY 4.3l Vortec 4WD ~83,000 miles (yes, that is the correct mileage)
I've been chasing a vibration for a couple months now. I recently bought a Jimmy from my grandparents but it had largely sat in a garage with minimal use. Going from rarely used to a daily driver was nearly catastrophic. Anyway, i got new tires and an alignment at the same time but after that the Jimmy started vibrating on the occasion when getting up to 65/70 MPH. At first the vibration was sporadic and inconsistent on when it would occur. The vibration was the whole vehicle and not just the steering wheel. it would sometimes go away when braking but would not get worse. now, fast forward to today, it vibrates worse when braking and that started after many of the fixes I mentioned below.
I had the tires rebalanced and road forced checked multiple times along with three alignments to no avail. I've replaced all four calipers (regreased slide pins multiple times for giggles), pads, rear rotors, resurfaced front rotors, replaced inner and outer tie rods, upper and lower control arm ball joints, idler arm and pitman arm, and nothing seems to have fixed the issue. Oh and new brake lines all around (one had internally collapsed). Now, with every replacement the issue lessons or gets slightly better but it still vibrates fairly heavily at high speed.
in addition to what I've done above since owning this vehicle for about 3 months I've flushed/back flushed the coolant system, transmission fluid and filter change, front and rear differential fluid flush/change, new output shaft seal on the rear differential since the old one was leaking, transfer case fluid change, new CV axles for the front because the boots blew on the drive from Illinois to Alabama (these were replaced a couple of weeks before the original alignment and when the problem started), new spark plugs and spark plug wires, and I'm sure I'm forgetting something. I have also inspected the driveshaft multiple times and the U joints are in good shape. there's no play of any kind in the driveshaft.
What i have found is that despite new calipers, pads, brake lines, etc the front brakes appear to be dragging. the rotors are heating up excessively and have heat marks. it is also difficult to turn the rotor/wheel because there is still pressure being applied. I have a new master cylinder on order but the thing is none of the symptoms that you would associate with a failing master cylinder or an ABS module are present but for the most part those two things really about the only thing left to replace.
I'm fairly confident that the problem is stemming from the fact that those brakes are still dragging but as mentioned the only thing left to replace his master cylinder and abs module so beyond that I'm at a loss.
I've been chasing a vibration for a couple months now. I recently bought a Jimmy from my grandparents but it had largely sat in a garage with minimal use. Going from rarely used to a daily driver was nearly catastrophic. Anyway, i got new tires and an alignment at the same time but after that the Jimmy started vibrating on the occasion when getting up to 65/70 MPH. At first the vibration was sporadic and inconsistent on when it would occur. The vibration was the whole vehicle and not just the steering wheel. it would sometimes go away when braking but would not get worse. now, fast forward to today, it vibrates worse when braking and that started after many of the fixes I mentioned below.
I had the tires rebalanced and road forced checked multiple times along with three alignments to no avail. I've replaced all four calipers (regreased slide pins multiple times for giggles), pads, rear rotors, resurfaced front rotors, replaced inner and outer tie rods, upper and lower control arm ball joints, idler arm and pitman arm, and nothing seems to have fixed the issue. Oh and new brake lines all around (one had internally collapsed). Now, with every replacement the issue lessons or gets slightly better but it still vibrates fairly heavily at high speed.
in addition to what I've done above since owning this vehicle for about 3 months I've flushed/back flushed the coolant system, transmission fluid and filter change, front and rear differential fluid flush/change, new output shaft seal on the rear differential since the old one was leaking, transfer case fluid change, new CV axles for the front because the boots blew on the drive from Illinois to Alabama (these were replaced a couple of weeks before the original alignment and when the problem started), new spark plugs and spark plug wires, and I'm sure I'm forgetting something. I have also inspected the driveshaft multiple times and the U joints are in good shape. there's no play of any kind in the driveshaft.
What i have found is that despite new calipers, pads, brake lines, etc the front brakes appear to be dragging. the rotors are heating up excessively and have heat marks. it is also difficult to turn the rotor/wheel because there is still pressure being applied. I have a new master cylinder on order but the thing is none of the symptoms that you would associate with a failing master cylinder or an ABS module are present but for the most part those two things really about the only thing left to replace.
I'm fairly confident that the problem is stemming from the fact that those brakes are still dragging but as mentioned the only thing left to replace his master cylinder and abs module so beyond that I'm at a loss.
BF Guru
Joined: Dec 2016
Posts: 5,588
From: Moscow, ID
Two ideas for you to consider:
1) Could you have pinched brake lines that are causing the calipers not to release?
2) I had a vibration issue on my 99 recently that I traced to the drive shafts. (I have several recent threads documenting my frustrations! LOL) Turned out I had a loose rear u-joint but also an overly stiff front u-joint that caused the vibrations. After the rear u-joint was replaced, I temporarily removed the front drive shaft the ride was completely smooth. There was no visible damage to the front drive shaft or u-joint!
You can drive without the front drive shaft as long as you don't put it into 4wd. I only drove it around town although I did several test runs up to 55 mph to confirm that the vibration was indeed gone.
To protect the machined surfaces of the splines of the transfer case output shaft from the elements, I covered it with a small sandwich bag and secured it with a couple zip ties.
Drive shaft imbalance vibrations will occur at all speeds and will be more noticeable the faster you go. Wheel imbalance will typically happen at only certain resonant speeds since they are attached to a spring system.
1) Could you have pinched brake lines that are causing the calipers not to release?
2) I had a vibration issue on my 99 recently that I traced to the drive shafts. (I have several recent threads documenting my frustrations! LOL) Turned out I had a loose rear u-joint but also an overly stiff front u-joint that caused the vibrations. After the rear u-joint was replaced, I temporarily removed the front drive shaft the ride was completely smooth. There was no visible damage to the front drive shaft or u-joint!
You can drive without the front drive shaft as long as you don't put it into 4wd. I only drove it around town although I did several test runs up to 55 mph to confirm that the vibration was indeed gone.
To protect the machined surfaces of the splines of the transfer case output shaft from the elements, I covered it with a small sandwich bag and secured it with a couple zip ties.
Drive shaft imbalance vibrations will occur at all speeds and will be more noticeable the faster you go. Wheel imbalance will typically happen at only certain resonant speeds since they are attached to a spring system.
Thread Starter
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New Member
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1. Pinched brake lines. It's unlikely. I replaced all four brake lines leading to the calipers and while there was an improvement it didn't fix the issue. At the same time, the issue didn't get worse.
2. I've read through a few of those threads and though I haven't replaced the U-joints I plan to do so and have them rebalanced at some point. That being said, I wouldn't expect to have a vibration when in 2WD that's associated with the front driveshaft as it shouldn't be spinning. While I do plan to do the maintenance on the rear driveshaft I doubt the issue is associated with it because I'd expect the vibration to originate from under my seat but it doesn't. The vibration feels like it's originating from the front end/front wheels and given that I've observed dragging of the front brakes that still seems to be the culprit. The thing is, other than the vibration there's no other symptoms that would typically be associated with a failed master cylinder or ABS module. I already have a replacement master cylinder so plan to replace it but the ABS module isn't manufactured anymore so have to buy one off ebay. I may replace both and get a full pressure brake flush and see what I get from that.
When it comes to the vibration, it starts out as nothing and then it appears and slowly increased without a change in speed. It only starts when driving at highway speeds but once it does and you slow down it'll continue. Previously it would stop if you dropped below say 60mph. Even more of a reason I still think it's associated with the brakes. I'm just tired of trying to replace every component in the system. lol
2. I've read through a few of those threads and though I haven't replaced the U-joints I plan to do so and have them rebalanced at some point. That being said, I wouldn't expect to have a vibration when in 2WD that's associated with the front driveshaft as it shouldn't be spinning. While I do plan to do the maintenance on the rear driveshaft I doubt the issue is associated with it because I'd expect the vibration to originate from under my seat but it doesn't. The vibration feels like it's originating from the front end/front wheels and given that I've observed dragging of the front brakes that still seems to be the culprit. The thing is, other than the vibration there's no other symptoms that would typically be associated with a failed master cylinder or ABS module. I already have a replacement master cylinder so plan to replace it but the ABS module isn't manufactured anymore so have to buy one off ebay. I may replace both and get a full pressure brake flush and see what I get from that.
When it comes to the vibration, it starts out as nothing and then it appears and slowly increased without a change in speed. It only starts when driving at highway speeds but once it does and you slow down it'll continue. Previously it would stop if you dropped below say 60mph. Even more of a reason I still think it's associated with the brakes. I'm just tired of trying to replace every component in the system. lol
BF Guru
Joined: Dec 2016
Posts: 5,588
From: Moscow, ID
1. Pinched brake lines. It's unlikely. I replaced all four brake lines leading to the calipers and while there was an improvement it didn't fix the issue. At the same time, the issue didn't get worse.
2. I've read through a few of those threads and though I haven't replaced the U-joints I plan to do so and have them rebalanced at some point. That being said, I wouldn't expect to have a vibration when in 2WD that's associated with the front driveshaft as it shouldn't be spinning. While I do plan to do the maintenance on the rear driveshaft I doubt the issue is associated with it because I'd expect the vibration to originate from under my seat but it doesn't. The vibration feels like it's originating from the front end/front wheels and given that I've observed dragging of the front brakes that still seems to be the culprit. The thing is, other than the vibration there's no other symptoms that would typically be associated with a failed master cylinder or ABS module. I already have a replacement master cylinder so plan to replace it but the ABS module isn't manufactured anymore so have to buy one off ebay. I may replace both and get a full pressure brake flush and see what I get from that.
When it comes to the vibration, it starts out as nothing and then it appears and slowly increased without a change in speed. It only starts when driving at highway speeds but once it does and you slow down it'll continue. Previously it would stop if you dropped below say 60mph. Even more of a reason I still think it's associated with the brakes. I'm just tired of trying to replace every component in the system. lol
2. I've read through a few of those threads and though I haven't replaced the U-joints I plan to do so and have them rebalanced at some point. That being said, I wouldn't expect to have a vibration when in 2WD that's associated with the front driveshaft as it shouldn't be spinning. While I do plan to do the maintenance on the rear driveshaft I doubt the issue is associated with it because I'd expect the vibration to originate from under my seat but it doesn't. The vibration feels like it's originating from the front end/front wheels and given that I've observed dragging of the front brakes that still seems to be the culprit. The thing is, other than the vibration there's no other symptoms that would typically be associated with a failed master cylinder or ABS module. I already have a replacement master cylinder so plan to replace it but the ABS module isn't manufactured anymore so have to buy one off ebay. I may replace both and get a full pressure brake flush and see what I get from that.
When it comes to the vibration, it starts out as nothing and then it appears and slowly increased without a change in speed. It only starts when driving at highway speeds but once it does and you slow down it'll continue. Previously it would stop if you dropped below say 60mph. Even more of a reason I still think it's associated with the brakes. I'm just tired of trying to replace every component in the system. lol
There are two things I'd as you to consider though.
I too thought the front drive shaft would not spin when in 2wd but on our second gen Blazers, at least those with the 4-button transfer case, the one with the Auto4wd feature, they do spin. I removed my front drive shaft and my vibration was eliminated. That is how I knew the source was with it somehow. I then found the front u-joint super stiff. The rear CV joint on it seemed fine though.
The second is that my vibration was most noticeable through the steering column and not through the seat. This made total sense after I found that driving with the front shaft removed made the vibration go away totally. This made sense since since the front differential is connected to the front wheels by the front drive shafts.
If it was not for the apparent elimination of the vibrations after you slow down, I'd bet on the problem being the front drive shaft.
However, because it is pretty easy to remove, I'd suggest removing it to see if it is the problem as an experiment. Just be sure to mark the alignment of the u-joint to the yoke on the front diff to get it back in its original configuration.
To protect the machined surfaces of the splined output shaft, I covered it with a trimmed sandwich bag that I secured with zip ties.
Whatever it turns out to be, be sure to report back.
P.S. You might look at this troubleshooting guide too. https://4xshaft.com/blogs/general-te...aft-vibrations
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