vibration between 25-50 and 70-85 any ideas?

[John Redcorn]

99 4wd. It just started doing this.

When you are on the gas accelerating or maintaining speed between 25-50 there's a vibration that gets stronger as you go faster but disappears at about 50mph.

I tired 4hi to see what happens, same thing.

If you let off the gas it instantly goes away.

If you shift down to second for higher engine rpm, vibration stays exactly the same, doesn't speed up.

It also seems to happen between 70-85. I've never gone faster than 85 in the tahoe but for some reason the last couple days there's been a couple times I did get going that fast.

I can't tell really where it's coming from. Any ideas what to look for? I have a bunch of work to do on it this weekend and this is kinda worrying me so it might be my top priority.

Friend suggested tires out of balance, they are but you don't notice until 65-70mph and tires out of balance would keep vibrating when you're coasting too

 

[Sepiroth]

Sounds like wheel balance issue. Try that first as that would be the cheaper way to go.

 

[718frankb]

change out the u-joints on the rear drive shaft.if you let it go too long you can do damage to the transfer case.about $30 in parts and 2 hrs labor

 

[peterey2]

ya def. check your u joints. put the truck up on jack stands or a lift and check for play in them.

 

[John Redcorn]

I think I'll do that.



someone has told me once I'd need an oxy-acetylene torch to get the Ujoints out if they're bad, said propane wouldn't work. any truth to this? alternative? BF-crowbar?

 

[peterey2]

if theyre factory u joints u will have to heat up the joint to get the nylon/wax piece out. if theyve been replaced before, you r&r them as usual.

 

[bowhunter22]

If you are checking your U-joints look for seized cups as well as the loose ones. Also look for dents or marks in the driveshaft that might indicate a bend.

 

[TahoeGoBoom]

check the front u joints too. thats what mine was when it did the same thing.

 

[John Redcorn]

check the front u joints too. thats what mine was when it did the same thing.

Even in 2hi? I know that shaft is spinning in 2 hi but without torque actually going through it would it cause vibration bad enough that everything in the rearview mirror is blurry?

My rear driveshaft is in question anyway. Previous to this vibration thing it was making pinging sounds on accelration and switching from D to R. We put it up on a lift in D and could hear sounds coming right from the middle of the rear drive shaft. No noise by the u joints. This was at a friends work (GMC dealer) and he said driveshafts can go bad, rare but he's seen them make a noise just like that when the do sometime.

It stopped making the noise mostly and started this vibration thing at the same time so I'm hoping that's all it is.

I talked to a driveshaft place today who are telling me that u joint sounds can do that, sound like they're coming from somewhere else like the middle of the driveshaft.

I think I'll just take the driveshaft to them. They can put u joints on, I don't want to mess with it if I have to have an acetylene torch. Knowing me I'd try without one get halfway through and have it so messed up I can't put it back together again. This place will test and balance the driveshaft too.


I haven't even looked at anything yet. Meant to this weekend but I didn't get my jackstands back from my brother who was borrowing them. (good excuse to get a lift kit!) they were 2 ton ac delco stands that made me nervous anyway they way they bent a little bit when I put weight on them. I got some new bigger ones from harbor freight today though, so I'm just going to pull out the drivesahft and let those guys deal with it.

 

[TahoeGoBoom]

Even in 2hi? I know that shaft is spinning in 2 hi but without torque actually going through it would it cause vibration bad enough that everything in the rearview mirror is blurry?

yep. did it the whole 200 miles home before i got it fixed. pinging, vibration, all that. but only while your on the gas. coasting, there was nothing. it was real weird. had it fixed, and its all better now. i didnt feel like fixing it tho, so i took it to a guy. 120 for both of the u joints on the front shaft. not too bad for me not havin to lift a finger. lol

 

[John Redcorn]

I just took the rear driveshaft out and the front ujoint on it is freaking shot. the yoke can rotate in either direction about an 1/8th of an inch making a crunchy sandy sound. The cups don't seem like they're seated right either, all lopsided. seems pretty bad so I'm hoping fixing that takes care of everything. (probably what 140k miles of the "thunk" gets you)

 

[John Redcorn]

It's fixed! I took the DS to them this morning they replaced both u joints and rebalanced it. It was done a couple hours later I went and picked it up and installed it at lunchtime. no more vibration, no more pings, no more thunk either.

The guy who did the work was out at lunch and the guy who I paid had no idea how out of balance it was so it's unknown whether it was out of balance enough to be a problem or if it was a ujoint(s). that front one was seriously screwed up though.

I'm sure the thunk will be back soon though, I didn't grease the yoke, i've read some very specific grease* is supposed to be the only thing to use there and I didn't have it so I'll wait.

*From here: http://www.gmfullsize.com/forum/showthread.php?t=146143 He's talking about transmissions but the same should apply to transfer cases.

You don't want to contaminate your tranny fluid with a foreign material such as a synthetic moly-grease that could coat the clutch plates, drums, bands, etc. causing slippage and ultimately total, catastrophic transmission failure.


ONLY use GM P/N 12345879 GM Performance Parts High-Temperature Grease

 

[vinmhslax15]

My truck has the same exact problem. Its way bad over 70 the whole front end shakes even. It also thuds when you initially push the gas. I already figured the u joints were going bad but today it got way worse. The check engine light came on and the car keeps coasting almost as if its on cruise control, it barely slows down at all. Also now i can feel shaking in the front end drivers side. What could be wrong now?

 

[1999HOE]

Hey tahoeyukonforums look it up its a lot more active for our trucks