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drive train vibration

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by J.Lance, Dec 19, 2002.

  1. J.Lance

    J.Lance 1/2 ton status

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    This is driving me nuts. I have a '90 Jimmy, all stock, 700R4 and NP241 TC. When I bought it about a year ago it had a vibration while under a load but I didn't worry too much because I had heard the driveshafts on these often needed balanced. I took the driveshaft in and had it cut and balanced. Vibration did not go away. Noticed my rear yoke was loose and pinion shaft seal was leaking bad. Replaced front and rear pinion bearings and seal. Pinion, Ring, spider, and side gears all looked excellent with good wear patterns. Vibration did not go away. Replaced axel bearings with axel savers and did a brake job while I was at it. Vibration still there. I don't know what else to do. Any suggestions would be great.

    At times it almost feels like the vibration is in the front end but that seems impossible because it goes away when you let off the gas and it's in 2wd. I'm wanting to possibly sell this vehicle but I don't want the next owner to have this problem.

    By the way, if anyone is interested in the purchase, it's fire engine red, an old fire department Jimmy. 114K miles. Runs excellent and is mechanically perfect except for the vibration. Absolutely no rust and nice wheels and tires. Warn hubs. It had been meticulously maintained by the Aurora Fire Dept. and I have maintenance records 1" thick. I'd like to sell it to buy another '71 or '72 so trades are possible. Not so sure about a price yet, depends on if I get it fixed. I paid $6K for it a year ago.

    Please Help! /forums/images/graemlins/confused.gif
     
  2. pplblazerdude

    pplblazerdude 1/2 ton status

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    I had the vibration problem to and i did a 180 degree flip on my drive shaft and it seems to havve gone away so try flipping ur drive shaft 180 degrees and that might work

    /forums/images/graemlins/k5.gif
     
  3. J.Lance

    J.Lance 1/2 ton status

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    I'll put that on my list of trouble shooting I'll be performing this weekend. Just got off the phone with another driveshaft shop and they said they'd recheck the shaft to make sure it was done correctly the first time.
     
  4. heavy4x4

    heavy4x4 1/2 ton status

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    I'm not trying to call you a liar...but that makes no sense from a mechanical standpoint.
     
  5. BigBurban350

    BigBurban350 1/2 ton status

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    Is that a full time 4wd? If so its probably your front end vibrating. You say it only vibrates under load, so if your drive chaft was unbalanced it should still vibrate at closed throttle coast because its still spinning. It could be something in your transmission or at your flywheel. If you really want to pinpoint this thing, located a facility with an EVA(Electronic Vibration Analyzer). You attach a magnetic sensor to what you think is vibrating and it will give you the vibration in a frequency. You then do some math(they should know if they have an EVA) with your speed, engine RPM and gear ratios to find out what is vibrating. They can also easly rebalance your drive shaft on the car if it is not excessive. /forums/images/graemlins/burb.gif
     
  6. J.Lance

    J.Lance 1/2 ton status

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    Which post were you referring to that makes no mechanical sense, just so we're straight?
     
  7. heavy4x4

    heavy4x4 1/2 ton status

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    pplblazerdude's post...the one I responded to.

    Because, if you think about it...if the driveshaft was the thing causing the vibrations (because it is bent/not balanced correctly), remounting it 180 degrees from normal would do nothing. It's still going to spin and send the same vibrations through the vehicle.
     
  8. J.Lance

    J.Lance 1/2 ton status

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    It is part time four wheel drive. A common method of troubleshooting vibrations is to determine if the vibration goes away under no load or at coast. If it does not go away, tires are most likely the cause, if it does go away and only vibrates under load, drive train issues are to blame. At no load there is some slack in the gear both in the rear diff and tranny/T-Case. Because of this slack, the driveshaft vibration may not be transferred into the passenger compartment like it is under load when all components are exerting force against one another. Therefore, if a vibration dissapears under no load you can not rule out the driveshaft being out of balance.

    If anybody with a reasonable amount of experience can dispute this and explain to me why I'm incorrect, please do. I'm by no means an expert and if I need correction I would greatly appreciate it. The last thing I want to do is feed incorrect information to anyone.

    If anyone knows of an EVA in the Denver area, please let me know. That would definitely be the way to go.

    Thanks. /forums/images/graemlins/grin.gif
     
  9. J.Lance

    J.Lance 1/2 ton status

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    I've heard of rotating 180 before. The reason being that the driveshaft may be out of balance with the pinion yoke since the shafts are balance without the yoke. The shaft/yoke assembly may be better balanced when rotated 180.
     
  10. heavy4x4

    heavy4x4 1/2 ton status

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    You're absolutely correct that the d-shafts are balanced as a separate unit...but I can't see that the balance/trueness of the t-case output or the axle yoke would make a significant difference. I've heard of screwed up/bent output shafts (ask polaris about that one /forums/images/graemlins/smirk.gif), but if yours is screwed up...what are the chances flipping you d-shaft will completely counter the effects???
    You can always try it, though, to give yourself piece of mind...just a matter of 4 little bolts and 15 minutes.
     
  11. J.Lance

    J.Lance 1/2 ton status

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    I'll give it a try and let you know how it goes. Definitely sounds too easy to work, but heh, if it works, that saves time and money so worth the 15 min. to find out and just for peace of mind. I have to eliminate all the possibilities before I take it down to the shop.
     
  12. HAMMERDOWN

    HAMMERDOWN Registered Member

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    When was your last ATF flush? If it's been a while, pop the cover, drain what you can, get a new filter in there, then take it for a full fluid flush at the shop (may be cheaper to do it all at the shop, but I doubt it). You'll only get about 4 or so quarts to drain when putting in the new filter, and it'll hold around 11 or 12 quarts (23 pints I think). You may need some TV cable adjustment as well. I had what sounds like the same problem with mine with roughly 30k miles on rebuilt 700. My TV cable also needed some adjusting. Burnt ATF and or improper TV cable settings can burn up a 700R4 really quick. Not driving in OD unless your at high RPMs is also a must. Just my $.02. Good luck
     
  13. J.Lance

    J.Lance 1/2 ton status

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    I'm confused. Are we talking apples to apples? Transmission flush for a drivetrain vibration? Wrong post?
     
  14. Dunc03

    Dunc03 1/2 ton status

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    I don't undestand your logic on only driving in overdrive at high RPM's. The purpose of overdrive is to keep Rpm's down and save gas and wear on the engine. Also it is not good to drive a 700R4 in 3rd for a continuos amount of time. The reason is that if the transmission is not allowed to shift into overdrive, then the torque converter will never lock up. If the converter doesn't lock up then it act like driving with a clutch partially depressed. This causes the engine and transmission to turn at different speeds. This will create excess heat which is the main reason that these trannies fail, aside from a misadjusted tv cable. I learned this from the guys at bowtie overdrive, they have published about a 10 page paper on how torque converters work. So don't take my word for it, check out there site Bowtie Overdrive. I know that this was the wrong post for this, just thought I'd explain.
     
  15. Dunc03

    Dunc03 1/2 ton status

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    I have the same problem with mine. My differential was extremely warn and wabbling. When I got it fixed it took out post of the vibration, but it started it again after it got broke in again. I just replaced the engine and tranny, and I pray taht it stops. If you figure it out before I do, let us know cause I know of alot of guys on here taht have the same problem.
     
  16. HAMMERDOWN

    HAMMERDOWN Registered Member

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    Okay maybe I mispoke-all I'm trying to say there is don't drive in OD, unless you are driving at high speeds. I've always heard this about 700R4's, and unless mine needs to be in 4th due to high RPM's in 3rd, I'm gonna keep it in 3rd, or manually shift it (since this problem anyway).

    As far as vibrations go, my rig was intermittently vibrating directly after shifting into 3rd, then it would vibrate even worse when shifting into 4th-nearly every time-for 10 secs or so. I'm talking B-130 vibrations-more like ridin over rumble strips. I to thought it could be in the front, as I could feel it in the steering wheel, along w/ everything in my cab shaking. When I let off the gas, it would quit. If I hit the gas, it would vibrate worse.

    Well, thought it was ujoints, redid them, then I thought it was the rear, redid it-out w/ the 12 in w/ the 14FF. Well then I thought it was the drive shaft, sept it only did it under load, so DS and tires are out. Then I thought it was my flexplate, as it had a fair amount of runout, but no cracks to be found. Then I thought it was my TConverter, maybe out of balance-or something. Which led me to trying the tran filter replace, then full ATF system flush, before I started in on the flexplate and/or TConv job, which is where I shoulda started in the first place.

    At any rate, vibration is gone, and has been since around August, and as far as I can tell, the ATF was the culprit. Maybe a clogged valve in the tran-I dunno. I did wind up adjusting my TVcable for later shifts into 3rd and 4th. Yeah, I probably have transmission damage to, but for now, its driving fine, and it only cost me around 100 bones total (if that much) for the filter and full ATF flush job, and a little over a half hour. BTW, nice link.
     
  17. J.Lance

    J.Lance 1/2 ton status

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    That clears things up quite a bit. I'd never thought of the tranny causing that type of vibration but makes since. Your the first to say you had a vibration and this is how you fixed it. It'd be worth the 100 bones to find out and it's a service that should be regularly done anyway, even if it doesn't cure the vibration. My vibration may be a little different than yours. Mine seems to be more speed related rather than what gear I'm in but I'll give it a try and let you know. Thanks. /forums/images/graemlins/thumb.gif
     
  18. Chris_T

    Chris_T 1/2 ton status

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    You can drive a 700R4 in 3rd no problem. In fact, if you check the owners manual they tell you not to drive in OD while towing. If you search for a discussion on 700R4 and towing it'll come up

    Edit> sorry, replied to wrong post
     

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