4wd gearshift vibrates with engine rpm

New member here. many years a lurker.

The 4wd gearshift has high frequency vibration with engine RPM when driving in 2wd . The shifter vibrates with the clutch engaged AND when disengaged while driving, vibration will increase with rpm increase.

The 4WD shifter does not vibrate when engaged in 4WD lo and high. The main transmission shifter does not vibrate under any conditions.

I turned the front drive shaft 180 degrees and that seemed to help a little bit. The U-joints are good upon inspection. The gear fluid is correct, the motor / transmission mounts seem ok too.

The wheels and tires are new and balanced. The engine and tranny are both recently rebuilt (by me) I did not open the transfer case when rebuilding the trans. I am competent with wrenches.

What could cause this nuisance vibration only through the 4WD shifter lever and only when disengaged (only when driving in 2WD)?

The vibration can't really be felt anywhere else (unless you're aware of it and are 'looking' for it in the gas pedal and cab bodywork / frame.

Hi and welcome to mightyram. This might be a difficult one to diagnose. First place I'd look is the centre carrier bearing the rear tail shaft. When they fail they rumble and force the 2 piece tail shaft out of alignment. If it appears to be in good shape then the actual tail shaft may be out of balance. If it's vibrating with and without the clutch engaged I would tend to think the issue isn't inside the transmission.
Just taking a guess on this one :shrug:

Thanks for the suggestion Geezer. The truck is looking at 200,000 of hard mileage. I took a leap of faith on the hardware (it wasn't running when acquired. So, you are probably right in diagnosing worn inards. Have restored it (four years and counting) Good news though,

Solved the vibration in the transfer case shift lever. Yea! The flange which bolts the shift lever down to the transmission case was missing its gasket. That gasket raises the shift lever a little bit up from the transmission internal shift rail. Without the gasket, it put the end of the shifter lever too deeply seated into the receiving shift rail inside the tranny. That was making the shifter vibrate with that rod.

I can’t tell from the manual, but there may supposed to be a bushing on the end of the transfer case shift lever to reduce vibration between the shifter and rail. Mine doesn’t have a bushing there and it would be too tight of a fit if it did have a plastic bushing there. The vibration is slayed now. I am still stumped why the 4WD shift lever vibrates at speed whether or not the clutch is engaged. The vibration follows the engine RPM regardless. That would indicate motor / transmission mount problem but I see no problems there…. Huhmmm…

I could not find the stepped input bearing for the transmission (discontinued) when rebuilding, so had to fabricate a similar (non-stepped) bearing to replace the unavailable one. It might have a little radial slop but as you mention, because it vibrates with or without clutch, that wouldn't seem to be a contributing factor.

The transfer case is part of the drivetrain that doesn't get disengaged. It will always have rotational input/output while the truck is in motion. I was also thinking it could be something related to selector forks or linkages being loaded up that was causing the feedback through the shift levers but you seem to have located it - nice work! (what do you need us for lol) Maybe check mounting bushes and bolts/cross members etc for something out of whack. You will always get 'some' harmonics through the truck. It's part of the character...

Thanks for that. I was wondering if the front drive shaft always rotated regardless of transfer case. Now I know that it does. I don't fully understand how the transfer case / locking hubs / front differential work (together or alone). You also pegged another issue with this truck. It was so rusty I have had to cut away and replace two crossmembers on the frame.

When I noticed the vibration that was my first fear, that the frame was tweaked from the repairs. I had to jack up one side of the frame quite a bit to get it level before welding in the crossmember which also supports the spare tire. It's all good though.

Originally, I felt the transfer case shifter was too high (floating) in the shift rail so I removed the gasket to make sure it was firmly engaged. So afterward when I noticed the vibration (not sure whether the vibration was a new issue) the thought occurred to me that maybe the problem had something to do with the (missing ) gasket. Otherwise, I would have never figured it out.

Some states have inherent rust issues due to the use of salt on the roads. Few vehicles survive unscathed from the rot monster. The transfer case simply disengages the front axle but the shaft will still rotate independently. The trucks have a trick to disengaging 4WD if it locks up too. You have to roll it in reverse a few feet to release 4x4 mode. It catches folks out if they aren't aware of it. Please post up some pics of your work for the voyeurs on the site. It's always good to see how members tackle repairs and it can inspire others to give it a shot or have an idea of how deep they'll need to go to get their truck fixed :thumbup:

Hello Suprabrew & :thumbup: KUDOS to you 'n WV Senator Joe Manchin

Wished I could rebuild a transmission OR at least find the parts 'n seals to keep it clean ~ FWIW Royal Purple 90W (?) gear oil helped my 5 speed tranny shift smoother & made the front input shaft bearing a little less noisy... I been emailing MitsubishiPartsCentral in Texas asking them to obtain as many transmission seals 'n software parts as possible BUT SO FAR they been kicking the can down the road (my regular MPC parts guy Gary just retired...)

I had a dream of removing my tranny to clean 35 years of grime off 'n paint it 'n reinstall ~ but renting one of these in Hawaii with delivery & pickup is about $500.00 one day RENT THIS: https://www.govdeals.com/index.cfm?f...0&acctid=19807

Shipping that sucker to Hawaii would be at least $2,000.00 maybe double..?

geezer came up with a great idea to stop the oil grime sludge forming on my tranny coming from the torn shift lever bellows rubber piece under the floorboard... geezer said McGiver a front wheel drive universal boot to fix the shift lever broken rubber part... geezer is good all the time...

OK CYA
George

I will try to upload pics again. Haven't quite mastered this website though, it's tougher to get through than a three-year-old rooster. LOL. I am grateful that it is here at all.

I am over 60 Y.O. and had always been terrified by ANY thought of opening a tranny. Maybe Ghostbuster monsters would come flying out and eat me alive. Who knows?. I had little to lose so I tried it. 'Tain't no big deal. Imperative to have factory shop manual or equivalent before starting and websurf until your eyes bleed before beginning.

I couldn't stop at just one so I rebuilt the tranny from my 4WD also. No problems, except the second time I over-tightened the final main shaft bolt and that prevented the gears from floating free (in neutral) so it didn't have a neutral. It would creep forward in neutral. So I had to pull it out again even before I put fresh lube in. Douwwh! I work outside and have to crawl on my belly like a reptile in the dirt when underneath the vehicle without any help; so 'pulling twice rebuilding once' was no fun. Plus, all those new gaskets I lovingly set with sealer, etc. had to be torn off and replaced in the the second attempt.

Of course, I would never open an automatic tranny because I am sure that Ghostbuster monsters WOULD come flying out and eat me alive in my dreams if I even thought about doing that....then again....

George, the tranny came from under the 4WD caked with gunk worse as i have EVER seen on any vehicle. The engine and engine bay were just as bad. The truck had been run with useless front and rear engine crankshaft oil seals until the driver finally forget to add oil to the crankcase while checking the fuel level (hehe, old Oklahoma driver joke) and seized the engine, ruining the crank, block and chewing the timing gears to confetti. It took q lot or gasoline and elbow grease to get the tranny case and engine bay back down to the level of the original paint.

One of those high-flutin' hot water steam cleaners would have been helpful, but it was so bad that scraping with putty knife would have still been required.

Yea, I am not native to WV and don't know what to make of Joe Manchin. All politicians are traitors these days, even the best of them should be drawn and quartered then fed to the hogs. Don't get me started on Jews LOL.

George, if I remember correctly, this is where I got the tranny rebuild kits for both the 2WD and 4WD vehicles:

https://www.drivetrain.com/parts-cat...d-overhaul-kit

I originally found them on EBay. Good kits with good bearings. I didn't buy the more expensive kits with synchronizers, etc. Didn't need them and have no regrets about that.

George, The only two issues with the tranny rebuilds are (were) that the "stepped" input bearing isn't available anymore / anywhere, neither Heaven or Hell has one. Second, that bearing needs a specialty bearing puller. I think I paid over $200 for that tool, used it twice, now it sits pretty in its cardboard box. That was the only 'special' tool I needed in the rebuilds.

I did have to buy an allen head socket that fit a ratchet wrench.

The vibration is from the carrier bearing on the rear shaft.

Thanks Camoit, I'll crawl under and take a look, while the sun is still being kind. Joke: What's the difference between a car and a woman? Punchline: I don't know, I've never been under a car.

You nailed it Camoit. The drive line carrier bearing is shot. Thanks for that, can't believe that got past me when reinstalling the drive shaft. It occurs to me that you MAY be referring to a carrier bearing in the differential pumpkin?

Anyway, have ordered the driveshaft support bearing and that should turn my little Ram into a Cadillac ride.