99 Tahoe won't shift to 4lo + a clunk

[hoeman]

Hi all! I'm new to this forum and a new owner of a 99 Tahoe. I love this truck!
Anywho, Ive got the push button 4wd transfer case. My problem is that it won't shift into 4lo. 4hi and 4auto works fine, but when I hit the 4lo button the light blinks for approx. 30 seconds then it goes back to the previous setting. Any ideas where to look for my problem.
One other issue is a clunk from the rear end, it clunks as you come to a stop, or when I start from a stopped position. I've read about the slip yoke making clunking noises and the use of a special grease to eliminate the problem (what kind of grease?), but I've also heard that it may be my factory limited slip. How do I check that my limited slip is working correctly?
Thanks
Here's a not so great pic cause I know everyone like pics.
:cheers:

 

[Slammed]

Hi and welcome
I dont have anything to add but I am too having the clunking problem but my 4x4lo works fine

when i come to a normal stop and the tahoe settles down it clunks and then when I take off it clunks again ?? All U-joints are solid any ideas?

 

[Rick90467]

No clunking here, but I do have to place my shifter in neutral so that 4LO will engage. If I leave it in drive even though not moving, mine will only go to 4HI, but the 4LO will act exactly like you describe.

 

[chevyrider]

well to add to that i too, have the "clunking" problem. I can't answer your question about the 4x4 low since i believe they all run on the same fuse. But for fun you might try changing out a new one it wont hurt anything to try. But i am curious if anyone has an answer to the clunking from start and stop i have had it since i got the truck and wouldnt mind getting rid of that problem. thanks and good luck on your 4x4.

 

[Slammed]

well its goo dto know I am not crazy LOL my mechanic says its my shocks but I dont think so I think its a tranny mount or somthing like that I will also check my spare tire

 

[96ProCompTahoe]

you have to put the truck in neutral and the manual recommends to be moving foreward slighty 1-3mph IIRC. theres a sensor on the T-case that shifts it into the differnet modes. it may be your problem if your doing everything correctly. (may be differnt on your autotrac version)

I have the clunk when the truck settles at a stop. it didn't show up till i had my lift installed. i'll be throwing in a new (better) slip yoke when it warms back up since its lifted. Not sure what causes the rear end clunk.

 

[96ProCompTahoe]

well its goo dto know I am not crazy LOL my mechanic says its my shocks but I dont think so I think its a tranny mount or somthing like that I will also check my spare tire

I have brand new shocks on mine, and the tranny hasn't been messed with before or after the lift, so it should be a mount. My spare tire is not the cause of the noise either.

Still have the clunk.

 

[Rollin Thunder]

the clunk i just it engaugeing, mine makes a slight clunk when shifting into LO, high is a click and low is a very slight clunk.

make sure your in N though. and if at all possable rolling a little bit.

 

[1999HOE]

i would recommend the having the wheel hub looked at my previous 98 blazer had that issue when coming to stops sounded like a pan being hit by a wooden spoon....

 

[hoeman]

First off I'd like to thank everyone for the replies.
I have been rolling in neutral when I try to shift to 4lo but it still won't go.
As for the clunk, I've noticed if I brake or accelerate more aggressively it seems like it is less pronounced.

 

[Slammed]

same here oh and you have to be fully stopped for low 4x4

First off I'd like to thank everyone for the replies.
I have been rolling in neutral when I try to shift to 4lo but it still won't go.
As for the clunk, I've noticed if I brake or accelerate more aggressively it seems like it is less pronounced.

 

[hoeman]

same here oh and you have to be fully stopped for low 4x4

Fully stopped or rolling it still won't shift into 4lo

 

[BraMas]

Mine did the same thing about a year ago. I narrowed it down to the buttons or the Transfer case motor. Well I started with the cheap thing and replaced the 4 buttons. Didn't work 4 LO would just flash at me. So I replace the transfer case motor and haven’t had a problem since. I'm 99.99% sure it's your TC motor
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=A1C&MfrPartNumber=48106&PartType=672&PTSet=A

 

[wht98yukon]

i have the clunk when i stop at lights or whatever, i was told it was my drum brakes or soemthing. doesnt really bother me, cuz my old 87 jimmy fullszie did same tihng as well as my moms old k5. i think of it as normal

 

[Stillakilla187]

The clunk is th u joint. just use a grease gun to shoot any automotive grease into the zerk on the u joint. That will keep it goin for awhile but the best thing to do is replace it its like 15 bucks. And for the 4LO just put it in neutral

 

[BraMas]

The clunk is th u joint. just use a grease gun to shoot any automotive grease into the zerk on the u joint. That will keep it goin for awhile but the best thing to do is replace it its like 15 bucks. And for the 4LO just put it in neutral

Thank you Mr. Obvious:ktoe: :lol: I'm pretty sure he know how to put it in 4lo
Trust me it's his TC motor

 

[Ikillrinst]

and its not the U joints either, I too have had this same problem for 6 years now, my transfer case locked up and tore my trans apart so i had both replaced.. The clunking started there after.. since then the trans has blown again and just 2 weeks ago the rear end went.. ALL U joints have been replaced and i still have this clunk. so 2 new trannies a new transfer case a new rear end and new U joints and still clunking... I think it is the rear springs. maybe the bushings are wearing... Any one care to chime in on how to tell if the spring bushings are going?

 

[GMCYukalade]

If your 4-lo isn't engaging in neutral.. than there is a problem with the t-case motor, But, i too had that clunk.. well i think its the same clunk.. its nothing of a metal sound but like a weird sound.. well, when my first rear-end came out, i replaced it w/ a limited slip rear-end and the clunk stopped... so i thought it was just the posi locker in the rearend clunking, but, i also replaced the u-joint - so it was either of those.. i know how a u-joint clunking sounds tho.. and that clunk sounded nothing like that



---edit---

I also replaced the end link bushings on the sway bar - don't know if that had anything to do with the clunk tho

 

[hoeman]

its been awhile, but i found the clunk. turns out the clunk was the slip yoke. pulled it out the other day and greased it up with some wheel bearing grease. i was very skeptical about this cause the clunk was pretty bad, and the splines seemed to have a lube on them already . to my suprise i put it back together and went for a ride, it's as smooth as silk!

as for the 4lo i still haven't looked in to it. i haven't needed it or had time to deal with it. i can't see it being the motor as it works fine when i shift to 4hi or 4auto. i'm thinking its just the switch.

 

[GMCYukalade]

The 4x4 switch on the dash? - they do go out.. 99s are bad for electrical problems.. - i've replaced my 4x4 switch once, the heater switch twice, and the headlight switch 3 times.. so.. - when the 4x4 switch went out, the lights wouldn't work any more - when in 2wd.. when put in 4x4 the light would come back on.. but placed back in 2wd no light, and it felt like it was still in 4x4