Grinding noise from front end when 4 wheel drive is engaged fj40 (1 Viewer)

[fjbend]

I am new to this thread, so first let me say thanks for all of the great advice I found on this website. I have an Fj40 that has been sitting for 5 years due to an overheating problem after a 350 installation. I took care of that issue thanks to these forums.
Here is my new problem. I can drive in 2 wheel drive with no problems. Yesterday, I wanted to test out the 4 wheel drive since it has been awhile. After locking the hubs and shifting to 4 wheel drive, I started driving. When I hit about 20 miles per hour and either let off the gas or shifted, I would get this grinding noise from somewhere in the front end. If I step on the gas, the noise goes away.
Today, changed the front differential gear oil to make sure it was full and to make sure there were no metal shavings. Everything looked good, but the noise is still there. I unlocked the hubs, kept it in 4 wheel drive, and I still got the noise. It is a pretty loud grinding noise. Any ideas?

 

[rsbcruiser]

A warn out output shaft bearing, maybe. Reach up there and grab the front driveshaft near the transfer output. Is it sloppy? repeat at the other end of the D.S.. Report back.

 

[Josie'sLandCruiser]

Hi All:

From your description I would guess something is up with the pinion in the front differential. Like the pinion gear is not set to spec, and it is obvious when not under load (coasting.)

Regards,

Alan

 

[Michael Hanson]

Sounds like a hub has gone out. MIke

 

[middlecalf]

Also, what happens when hubs are locked but in 2WD (front diff will turn but not under load)? Seems like something in the drive train before the front diff.

 

[cruiserheads]

Driveshaft too close to skid plate maybe.

Neil.

 

[twoturtlesracing]

Mine does this too... I'm pretty sure that it is either bad caster angle, or slop on the splines on my front driveshaft, as it did not do this before my lift... Hope it's something simple for ya!

 

[Josie'sLandCruiser]

Hi All:

Ha, ha! X 2 !!

This actually happened to me a few years ago. Installed a "new" (from another FJ40) stock skid plate on my rig right before the first run of the season.

Drove to the trail head, aired-down and engaged 4wd low-range. Grinding noise as the rig goes down the trail. Tried several different combos and kept getting a grinding noise. Finished the trail in 2 wd low-range.

That afternoon in camp while diagnosing the grinding noise discovered the front drive shaft interference with the front lip of the skid plate.

Regards,

Alan

Driveshaft too close to skid plate maybe.

Neil.

 

[65swb45]

A warn out output shaft bearing, maybe. Reach up there and grab the front driveshaft near the transfer output. Is it sloppy? repeat at the other end of the D.S.. Report back.

My thought too. Put it in 2wd and spin the driveshaft by hand. Chances are you will feel the growl in the front output bearing of the t-case.

I have seen a number of these go bad from lack of use.

Use it or lose it!

Best

Mark A.

 

[fjbend]

Results

Thanks for all of the responses. I did some more testing after work today. Here is what I found:
I grabbed the drive shaft near the differential, and there was slight movement, but I would say somewhere around 1/16" of an inch. I grabbed it close to the transfer case, and it had almost no play.
I rotated the driveshaft by hand, and it spun freely. I could not hear any noises, and it spun easily.
I locked the hubs, kept it in 2 wheel drive, and took it for a spin. There was no grinding noise, so it only does it in 4 wheel drive with and without the hubs locked.
There doesn't seem to be a skid plate issue, so I am guessing it is in the transfer case somewhere. Any ideas?
Regarding the use it or lose it, I agree. Unfortunately, I dropped the 350 in there, had overheating problems, got married and had kids - AKA no money. I think I might have been a dead man if I used it.
Thanks for the help

 

[twoturtlesracing]

Another quick thought for you, in the intrest of a simple, easy to fix problem... Is there anyway that you're front driveshaft is out of phase? That'll make awful sounds too at any kind of speed. Ask me how I know...

 

[fjbend]

Thanks, I will look into that, although I am afraid that I might have to do a transfer case rebuild. It doesn't sound fun.

 

[Josie'sLandCruiser]

Hi All:

IIRC you should be able to replace the front output shaft bearing in the t-case without removing the 'case from the truck.

But, you said the front output shaft was tight?

Go find an auto shop that will allow you to put your FJ40 on their hydraulic lift and run the truck in 4wd with the tires in the air. Then you can get under the rig and try to narrow-down where the noise is coming from while someone puts it in/out of gear.

Good luck!

Alan

 

[fjbend]

I think I will try that. I replaced the transfer case fluid today, but still have the noise. It took less than 2 quarts, which is less than I was expecting, but it was coming out of the fill hole, so it guess it only takes that much.

 

[mattcamp]

Can you post a picture of the front diff and the drive shaft, there might be undue pressure on your pinion due to the angle it is at, especially if you have a lift which has changed it. If your hubs are unlocked and you engage the front end it will turn, and if your four wheel drive is disengaged and your hubs are locked in, it will turn, thats why I suspect it might be an issue. You could eliminate your axles and hubs by driving with it in two wheel and only locking one hub at a time and listening. This will nail down one side of the axle or the other and not turn the front driveshaft. Are you catching where I'm going? Try pinpointing it , but still post a pic.. -Matt

 

[fjbend]

Got it. I will take some photos and do some more testing hopefully tonight but it might have to be tomorrow. Thanks everyone for the input.

 

[fjbend]

I made it home at lunch today to do some testing/take photos.
Here is what happened:
2wd, hubs locked - No noise
4wd, hubs unlocked - grinding
2wd, left hub locked - no noise
2wd, right hub locked - no noise
4wd, hubs locked - grinding
4 low, hubs locked, grinding
Here is a link to a video I took where you can hopefully hear the noise:
YouTube - P1010564

Also attached are some photos of the driveshaft.
Thanks for the help.

 

[fjbend]

I will have to decrease the size of the photos. I will do that later tonight.

 

[FJforty]

You could drop your front driveshaft and put it in 4wd. That will isolate to the transfer case/tranny from the diff.

 

[rusty_tlc]

Checking the phase on the drive shaft is a good idea that you can take care of pretty easy and may solve your problem,

You could drop your front driveshaft and put it in 4wd. That will isolate to the transfer case/tranny from the diff.

That's another very good suggestion.

With the drive shaft out you could also jack up the front wheels, lock the hubs and spin the pinion by hand to see if it feels rough.