1999 Suburban 4x4 Question

[joesregalproject]

Steve, so more or less your saying it's fine, but shifting the transmission to neutral before shifting the transfer case puts less wear on both components, as well as makes for a smoother shift?

Also I asked the same question on GMT400.com which is a forum for these trucks and they say a little bit of motion is normal while the actuator on the front diff is being engaged.

 

[joesregalproject]

The more I research this (and there honestly isn't a lot of literature on this, I've been scanning forums like crazy) the more I'm finding this "hard shift" is normal. Seems to be that these "shift on the fly" type electronic transfer cases, regardless of manufacturer, be it Chevy, Ford, or Jeep, prefer to be shifted on the fly as opposed to from a stop. I guess that is just the case for mine.

 

[pontiacgp]

You are not the only one finding a problem to get information on this. I was trying to find out how the trans axle works and to see what components are used. I found some guys saying you should be moving to shift from 2hi to 4hi and one poster said you can shift it up to 55 mph but I could not find any other info than what people are posting.

 

[joesregalproject]

Well thanks for all your help, Steve. And yes, there is a lot of contradicting information all over the web written by people who all 'claim' to be mechanics, and it's almost enough to drive you crazy. Now having researched a little more, I found out the case is a GM NP-246. And It seems the bigger problem these t-cases have is the internal pump can rub against the rear case and create a pinhole in the case. Mine doesn't seem to have that pinhole yet, so I guess I'm not going to fix it if it isn't broken. When it does break, I'll probably just replace the entire case with a remanufactured unit. Otherwise I've really taken a liking to this truck!

 

[pontiacgp]

I think those trucks are awesome. I always liked the Yukon and almost bought one but the Jeep was a better price.

 

[Geo's66]

We have a 96 2dr Tahoe and a 2012 Tahoe. The 2012 manual says to be rolling but less than 20mph to shift into high 4wd and barley rolling to low 4wd... Do the same on the 96. Try gmfullsize.com and go to the OBS section- ton of guys on their for everything, like here... I love that box style truck... Let us know.

 

[84_SS]

I had a 99 Tahoe and it did the same thing. you can shift from 2hi to 4hi while driving, I never did it under heavy throttle, but if you are just cruising along you should be Ok. But that being said NEVER shift it into low while driving, always has to be in neutral. I know a lot of these transfer cases are actually chain driven (I played with a fair amount of jeeps, which use a similar transfer case) so a lot of the time there is a little slack that gets tightened up, that might explain your hard shift.

 

[pontiacgp]

My Jeep is chain driven and if you get stuck in 2 wheel dive you can put it into 4 wheel drive while stopped but it won't engage until you start moving. I was trying to find out if the GM was similar so thanks for that info

 

[84_SS]

is the jeep electronically shifted? I never had this problem with my jeep.

 

[pontiacgp]

no, it shifted with the stick, it will shift easy enough when stopped but like a bicycle it won't shift into gear until you are moving. That was the way it was on my 99 Cherokee Sport