gear shift rattles at higher rpm's

[Middle man]

My next project with my 720 is huntin down the cause of the rattle on my gear shift knob. At high rpms my hand shakes on the knob.It only has 34k on it so I'am hopeing its not he tranny.I will attempt to change the center bearing and universal joints.Another thread suggested while doing so replace rear seal in tranny tail...good idea. Any body have this issue? The rattle is not relaxing,I keep thinking tow truck while driving! Want to solve this issue before I take a long trip. Thanks

[ownTer]

How bad is the vibration? Mine makes fair bit a racket. But i toss it up to the fact that its a Datsun.

[datzenmike]

The rear seal is just a good idea because it's easy to get at with the driveshaft out.

Likely the U joint(s) but equally the rubber doughnut surrounding the center bearing has rotted away. The bearing is very unlikely to go bad but the rubber support is. Without it, the driveshaft will become unstable.

 

Tires out of balance is another.

 

Loose or damaged transmission rubber mount.

 

Loose engine to transmission bolts.

 

Worn/damaged clutch disc.

[Middle man]

Yeah the doughnut looks and feels like part of the frame its shot. I'll call autozone today see if they got the parts.Its the type of noise that you know its tearing itself up and I am not livin with that. I enjoy this old ride.Wish me luck Iam goin in!

[datzenmike]

I have, with good results, wrapped a strip of rubber around the center bearing sleeve and clamped the metal hanger over it. It was intended to be temp fix but forgot about it. Smoothed the ride out.

[Middle man]

Wow that blows me away,Mike!!!  I priced the parts just now,$108.00 not bad. But your idea gets me out of town sooner,and confirms the issue. Can I ask is that a 360 degree shim or just across the top? also is that a hard rubber shim or??? Haven't removed the carrier bracket yet,so I don't what to expect for clearance. I don't know why I didn't consider this to at least isolate the issue.Thank you

[84720FourWheel]

It was conveyor belt rubber IIRC from the last time it was explained. Search for carrier bearing in the search bar. Should come up there, as it's a common issues.

[Middle man]

After prying the rear shaft out, I noticed the stiff u joint,chunked out carrier rubber and mostly the oil leak from tranny tail seal. Were goin all new. Not to costly and I'll feel better goin down the road.Another thread says autozone u joints don't hold up,so I'am goin with precision. They say to change carrier every 10 yrs. but  by then it will be my kids problem,I'll probably be wearing depends by then so it will be there issue. lol. Great gear oil suggestions? cause I know I'll lose some pullin the shaft out. And yes mike I will inspect or change tranny mount,again...thanks

[84720FourWheel]

Any GL4 gear oil. It can't be GL5 rated, or your kids are going to need to rebuild the tranny.

 

The syncros are made of a brass copper alloy, and gl5 gear oils have additives that damage the metal. Pennzoil makes a fluid for old GM synchromesh, Royal Purple is yellow metal safe but is very expensive, Redline makes a yellow metal safe tranny fluid, as does amsoil. In a pinch you can use 20w50 engine oil as well.

[datzenmike]

Cut a strip wide enough to fit the metal hanger. Make it too long and test fit until the hanger clamps it down tight enough so it isn't coming off.  Anything will do that is flexible enough to wrap around the driveshaft yet is 1/4" or thicker. I found a piece of conveyor belt from a gravel pit. (free for the asking) It has nylon cord renforcement just like tire rubber. Try to find a really old nylon tire without the metal cords, a real old one. Cut the tread off in a strip and try that.

 

The original rubber doughnut is quite firm and the belt might be firmer but like I said it worked so well I just left it.

[Middle man]

Now I gotta wait 3-5 days for parts,i will update when finished. Fingers crossed!

[banzai510(hainz)]

if truck is lowered alot then you need a spacer under the carrier bearing

[Middle man]

Yeah I could not wait till the parts got here,I want to drive this rv everyday.So while waiting I pulled the carrier bracket,zip tied 2 inch piece of rubber to the inside [i could see the smooth marks where it was turning inside] and added stainless bolts to mount it. Almost all the rattle is gone,it worked! Mike your 2 for 2 thanks. This for me is fun. Side note: Helped a homeless vet install the same thing in his larger motor home,he did not have any money and he was told he needed a new carrier bearing. With a gas voucher he is headed home today,it worked for him also. Pay it forward...you guys pat yourselves on the back!

[datzenmike]

The actual carrier bearing has almost no load on it. I can't say they never go bad because we had a member claim his was, but other than that have never seen a confirmed bad bearing. People change them because it's in the replacement kit. The driveshaft just needs some stabilizing by the rubber isolator.

[Middle man]

2 wks. ago I would not have known how to help this guy. I dig this shit!!!