Grinding when engaging 4lo

I posted this on ih8mud a few months ago and didn't get any responses so trying here...

Too Long; Didn't Read summary: 4lo sometimes won't engage and is accompanied by sound of grinding gears.

Hey folks, I bought a 2015 Tundra TRD Pro with 92k miles on it. I've had it about 2 years...my first 4x4 and first Toyota. Engaging 4hi always works perfectly. About 50% of the time when I try to engage 4lo it works and the other 50% it just sits there and beeps with the traction control light blinking. Sometimes it goes into 4lo easily as it should but then I can't get it out of 4l (again just beeping). Usually I turn the knob back to 4lo, shift from neutral to drive, pull forward a little and try the process again and usually after 2 or three attempts I can get back to 4hi. Sometimes the process of going into or out of 4lo is accompanied by a gear grinding noise like you're shifting a manual without quite having the clutch in all the way. On one trip I was quite a ways in the back woods down a fairly steep mountain dirt/rutted road and it started raining so I turned around wanting to get out before the road got worse. I had a hard time getting it into 4lo but finally did and started driving and within 50 feet there was a loud clunk with a jolt (thought I might have hit a rock with the diff or something) and I was still in drive but the truck acted like I was in neutral...no forward reverse or park. When I would try to shift I just got loud gears grinding. Thought I was stuck in the middle of nowhere for the night. I put it in park, turned truck off, put e-brake on got out and looked for any damage. Couldn't see anything wrong. Can't remember exactly what I did but just kept playing with it until I finally had a working transmission and was back in 4hi. Obviously I am pretty gun shy about trying to use 4lo now. Dealer put it on the lift and of course it worked perfectly for them. Any ideas/suggestions?

 

This thread may help.

https://www.tundras.com/threads/2007-2020-transfer-case-actuator.61182/

 

Man, I know the shop said they didn't see anything, but you know there's obviously something up; I'd get it back into the shop and get another opinion/set of eyes on it. Maybe take a video of what it's doing so if it happens again where it works when you bring it in, at least you have something to show them.

 

Going to 4-Lo can be a pain because you're trying to get gears to mesh and with around 2.6 reduction it can be difficult. I have not had the Toyota 4-X but my Jeeps or Ford Explorers would be as difficult and I resolve it by trying to find a slight decline or incline in road, stop and put transmission neutral take foot off brake and all to roll slightly why shifting to 4-LO. This movement allowed the gears to mesh without grinding or fighting the issue. Good Luck

 

A little bit of grinding going into 4 low is normal or somewhat expected as synchronizers are attempting to line up two shafts at different speed.

I've had 5 5th gen 4runners including a trd pro with manual shifter and they all clunked and grinded a bit.

But not fully engaging is an actuator issue either with the ADD front diff or the transfer case selector actuator.

 

Being in neutral and letting off the brake to allow for freewheelin' of the drive train usually works for me. Yours sounds like it may have a bigger issue though.

 

Thanks all!

@Downytide - thanks for that thread...that sounds like it could be the issue. Going to crawl under and look at that actuator to see if the hose has come off.

@Kfrog - thanks for the info. I'll give the incline idea a try!