Squeak only in 4wd

Hi all first post here, sorry if I need to move it/do anything different. I seem to have a somewhat unique problem with my 2016 sr5 I can’t find any forums on.

Recently when putting it in 4wd (which I do less than I’d like to admit… maybe 4 times a year.) I noticed a squeak in a “rotational” cadence. It’s not constant, seems to come and go. Varies with vehicle speed. Seems to go away around 15mph and higher. Does not seem to change while turning/going straight. Immediately goes away once out of 4wd.

Truck has 100k on it. Just greased the drive shafts/u joints with no change in the squeak. Crawled under it and checked that the front drive shaft looks fine. Spins freely by hand without grinding/squeak. (In 2wd, I’ll check it out parked in 4wd tomorrow.) I’m fairly certain it acts the same in both 4 high and low. I’ll attempt to confirm tomorrow.

Besides putting all 4 corners on Jack stands and crawling under it while in 4wd I’m not sure what to check next. Admittedly I’m a bit hesitant to do that test… and would like to avoid that if possible haha

Am I right to assume I should isolate this to the transfer case, front drive shaft, and front diff since the front axels rotate at all times?

Thoughts or suggestions appreciated!

 

The culprit is likely to be a failing universal joint (U-Joint), which is a component of the driveshaft. Did you check that yet? I agree that putting in jack stands (or even better, on a lift) so you can get under it while it's in 4wd Hi/Low and with the wheels turning, but that is dangerous and difficult to do.

 

Have you ever greased the zerks?

 

What’s the best way to check for a failing front u joint? I’ve crawled under it and tried to hold both sides by hand and didn’t notice any play. Don’t see anything concerning with them.

I have greased the unjoint and slip joint zerks. The slip joints looked dry but I didn’t want to over grease them. Gave them three pumps or so and drove it. Still seemed dry so I gave it some more before driving today. Unfortunately I didn’t come across any terrain that called for 4wd so I’m not sure if the second round of greasing the slip joint did anything.

 

Update!
After the second round of greasing the drive shafts, I took the truck for a spin around a parking lot in 4wd. (I didn’t make any 90 degree turns and bind up the drivetrain like some of yall freak out about so I don’t wanna hear it) I could not replicate the squeak. So either the second round of grease fixed my issue or it’s only when under an uphill, rocky incline. I’ll post back here next chance I get some real world 4wd use.

Side note, I parked the truck in 4wd and climbed under it to try and rotate the front driveshaft. It was locked up solid with no movement whatsoever so I’d think that eliminates the potential of a u joint issue!

Thanks for the help and happy wheeling!

 

You can’t over grease the U joints because they are not sealed. It will just escape from the open spaces. Definitely do it every oil change.

Normal. 2wd will unlock it.

 

Does that apply to the slip joint or just the u joints?

 

The slip joint I’m more cautious and only do about 5 pumps an oil change due to the tighter tolerances while the U joints normally fling grease out so I pump until I see fresh grease.