kmghawaii

DRIVELINE/TRAN VIBRATION ONLY IN 5th @ CERTAIN RPMS

I have a 82 Pickup 4x4 but I am only getting vibration in 5th at about 2000-2200 RPM when I am on the gas (engine on load), the vibration lessens as RPMs increase but does not go away. Its only in 5th and at those RPMs. Just replaced the U-joints and it is still occurring. Does anyone have any ideas on whats going on? Synchros? Unbalanced drive shaft? Gearing?

RobotMoose

iTrader: (1)

I had that problem. It was a combination of unbalanced wheels and an unbalanced driveshaft.

naylor2009

well i have my 83 4x4 it has the same problem! i seem to feel it alot in the frontend. i've replaced u-joint,tie rod ends,rebuilt the drag link, new wheel bearing. i haven't got the slightest clue its kinda pissing me off so if there is anything else you can think of please hit me up. i was thinking maybe the trans/transfer case mount! what do you think?

ThatGuy1295

I have the same problem with my 01 tacoma. Like exact same symptoms. I have replaced U-joints at both ends, but not the CV in the center yet.

kmghawaii

ok so i did little work on mines...changed both u-joints, tightened the output shaft bolt on the transfer case, and lined up all the yokes on the driveshaft and the vibration lessened...its not gone completely but a HUGE difference. my next option is to check the ring and pinion on the rear end as well as the lash on the driveshaft. once I finish the gears i will let you guys know again. let me know if you found some info/remedies!

ThatGuy1295

Doubt its your rear diff at all. It wouldn't be specific to which gear your in. Unless 5th gear is multiplying the vibration to a level in which its noticeable because its OD or (geared up). But you would think it should still be noticable at all speeds and gears, just less.

kmghawaii Is your truck a King cab (2 piece Drive Line) or standard cab? As the CV part of the shaft is something to consider. Im not sure if the 82 had king cabs or were even 2 piece DL if they did, but I have to ask.

Like I mentioned above my situation sounds excactly like yours, except with a 2001 taco. Strange part is after removing the DL multiple times the vibration always went away for the first 10-15 Miles after reinstalling the DL. Then it came back and was exactly the same as before. The only U-joints I havent replaced on mine are the 2 CV joints in the middle. Seems like every time I mess with it the vib stops for a few. I know for a fact that every time I removed the DL I maxed out the CV shaft in the process of removing it, could be a bad U-joint in there and its like a bad knee, stretch it out and its good for a day or so, but its still a bad knee.

Anyways its all speculation at this point. Only real way to figure it out is to start replaceing stuff, sure.

Also have to ask, have you done any suspension mods that would alter the pinion angle prior to this vibration occurring??

kmghawaii

ya i thought the same...i figured it would vibrate in any gear at any speed if it was joints/unbalanced driveshaft. i was hoping it wasnt trans problems, but 5th is a hard gear to break in my opinion only because it is rarely used and if it is then it would be used only when you are coasting.

my truck is a short box standard cab with a 1 piece driveshaft. my suspension is stock other than shocks, so i did nothing to mess with the stock geometry.

same here, all just a mystery at this point. i already planned on changing the gears because the stock just arent enough. so i figure do it anyway and see what happens.

dropzone

iTrader: (6)

Must have tightened the output shaft nut..no bolt.
What did you torque it to?

Since it is only noticed in 5th gear I would guess it is fifth gear shaft. had a similar issue with my original 5 speed but I destroyed it before it became an issue.

Thatguy: 1st Gen trucks never had an extra cab..those came out in '84 unless you have a Fabco converted Custom Cab..

kmghawaii

oh yup my bad, it was the output nut. i didnt torque it. i just tightened till here was no play in the shaft. what should it be torqued to? i have never tried to replace the 5th shaft or any for that matter. something difficult/expensive? where can i get them? thanks for the input and info.

suncomb1

All 1979-1983 trucks vibrate to some extent when in 5th gear and 4WD is engaged. I have never noticed any vibration in 5th gear when in 2WD. I have owned a 1979, 1981 and my present 1983. I would say your problem is in the transmission.

RobotMoose

iTrader: (1)

This actually makes alot of sense.
I had this same problem and chalked it up with my wheels salvaged from a '72 FJ40 and tired driveshafts.
I had new shafts made when I rebuilt the transmission an assumed the newly balanced shafts chased off the vibes. If it was the prop shaft vibrating on a tired bearing, it explains a lot.