Grinding while shifting Transfer case from 2HI to 4HI

[BC2500HD]

I was heading up skiing yesterday, and as I was heading up the mountain. There was snow accumulating on the road. So, I switched from 2hi to 4hi. There was a very noticible clunk/grind, and then it was in 4hi and worked as normal. Disengaging from 4hi to 2hi was normal. It works fine if I stop and engage. 4LO is normal.

 

Today I crawled underneath and check the fluid. Full. I just put new fluid in 3-4K ago. It looked good as it ran out of fill plug.

 

This is my 3rd GM truck with the electronic transfer case, and my other trucks never had this problem. Just in case my profile isn't updated. My current truck is a 2001 Silverado 3500 8.1 w/Ali trans.

 

I've tried searching on the Internet, but mostly find out about pump rub problems. Any ideas?

[RagsNB]

Not sure if that particular truck has a glitch but that same symptom appears in all trannys at some point. Usually at start of season when 4 wheel has not been used much or in really cold weather with lots of snow or ice accumulation up under. The issue is always the same cause vehicle was not full stopped with rpm down to idle when shifted in or out. Or ice and snow wedged the shift mech not full out or not fully in. Happened to me other day in my 1998 6.5 TD and just came to full stop put it in neatral made sure rpms dropped then shifted back in to 4 wheel and out and started again problem gone. Also happened last week in my 2005 2500HD again same issue didnt full stop in neatral with rpm low nd reshifted and all solved. Both these 4 wheel drive engagements where first of the season so trucks had been out of 4 wheel for past 6 months.

Just make sure you full stop fully in neutral rpm dropped and shift into 4 wheel and do same on way out. Some times when coming out you need to back up for 10 feet and then forward to get it to disengage. again especially when first shifts into 4 of the year or after heavy snow rain slush gets uo under truck and freezes.

 

Just my view of it over the years and many different trannys....they all seem to work the same. So in e end I would not worry about it unless it happens everytime.

 

Rags

[BC2500HD]

In my last 2 trucks I could shift into 4HI at 50-60 mph. "Shift on the fly"

 

When I bought and test drove the truck a year ago it didn't do it.

 

I wonder if the front diff actuator isn't engaging diff before TC control shifts TC?

 

Just to clarify my truck has electronic TC.

 

I tried it twice and still does it at speed.

[RagsNB]

BC,

If you have the push button shift yes you can do that on the fly by owners manual....not safely in my view but you can. Usually one wants to shift into 4 wheel at N or almost crawl. If you have older system non push button like on my 05 Silverado and 98 Sierra ya do it at a stop.

 

Rags

[dewfpo]

I always make sure I am off the gas whenever I shift the transfer case from one mode to another so there's not any torque buildup on the components that are trying to shift. I shift on the fly as well but the wheels are straight ahead and I'm off the go pedal.

 

DEWFPO

[BlackZ71Silverado]

The only time you have to shift into Neutral is when shifting into/ out of 4LO.

There is absolutely no need to do so with 4HI.

Electronic shift is shift on the fly, it's designed to do so and will not harm anything. Just be sure to do so at a common sense speed. Slowing to a crawl and/or shifting to neutral as suggested above is not necessary.

 

 

Sent from my crappy iPhone 6

using Tapatalk

[BC2500HD]

That has been my experience with these trucks too. I forget what speed the max speed the manual says, but 40-50 mph is ok I think.

 

It seems like a synchro problem. Maybe the computer programming needs an update or front diff actuator isn't working properly. I think both drive shafts should be spinning at the same rate before the TC shifts?

 

Just trying to avoid a trip to The Stealer!!

[00Silverado4x4]

Is it possible that your rear wheels were slipping when you hit the button? If they were, that would cause a grind as well. In my previous Sonoma I had that problem a few time. I just had to remember to let off the gas pedal when I wanted to shift into 4wd or at the very least, not spinning the rear wheels.

[BC2500HD]

I've tried using it again, over the holidays. First try....I slowed down to 30mph and let off gas. It made the grind. Just not as loud. Second try....slowed down....then shifted trans into neutral. It made the grind.....

 

I don't think on any of my tries I've been spinning the rear wheels.