Using the Autotrac unit???

blazerguy01 · November 12, 2004

Hello new guy here,

I just bought a like new 2001 Blazer ls. the salesman told me when i engage the Autotrac to be sure it is at 35mph or less..

Are there any offical instructions for using the Autotrac ( its not in the manual)???

(2wd-4hi-4low)

Please let me know

scott

chevroletmb · November 13, 2004

i've never heard a top speed for engauging auto 4wd

the electronic shift will take care of everything for shifting in and out of

4hi - auto- 2wd but for 4low u should be rolling below say 5mph but not stopped

and transmission in neutral then shift in and out of 4low

sub5 · November 13, 2004

Yep, that's right. 4hi - auto- 2wd you can shift on the fly. CHEVROLETMB said like it is except not recomended to use the 4wd on dry paved roads especially when taking tight turns. You can cause a lot of damage to either the transfer case, front axles, or both.

chevroletmb · November 13, 2004

exactly with all 4 wheels being driven the slippage is either by the tires or

serious wear and tear on the t-case

vhato · November 13, 2004

exactly with all 4 wheels being driven the slippage is either by the tires or
serious wear and tear on the t-case

<{POST_SNAPBACK}>

A little more detail will be...

When using the AutroTrac T-case a clutch pack is used to engaged the front d-shaft. Some pressure is ALWAYS present on this clutch pack which is why the front shaft always spins. In 4WD Hi/Low the computer applies 100% pressure to the clutch pack which is where T-case damage comes from on hard surfaces. The clutches wear out QUICK.

In Auto Mode less than 100% (I dunno how much) is ever applied allowing some clutch slip which allows hard surface use.

chevroletmb · November 13, 2004

if the encoder motor has 100% applied to the clutch pack the clutches should not

slip and thus not wear from my experiance the clutch only wear if they don't

release completely ie dragging when unappplied usually caused by insuficien (sp)

cluch pack clearance

blazerguy01 · November 16, 2004

4hi - auto- 2wd but for 4low u should be rolling below say 5mph but not stopped

and transmission in neutral then shift in and out of 4low

Thank you for everyones replys.

chevroletmb you mean that i should put it into neutral on the column before hitting the 4 low??? looks like you get a lot of experience up in Alberta using the Autotrac.....this will be my first new york winter with mine...

Scott

chevroletmb · November 16, 2004

yes that's right neutral in the transmission before 4low and out of 4low

yeah just part of the job when you work for a highly truck oriented dealership

sub5 · November 16, 2004

chevroletmb Did you ever service an AUTOTRAC T-case? Mine has 200k km and is starting to loose oil from the seals, not a lot but it's starting. Also lately I'm OK in 2wd & 4w auto, but the 4wd Hi & Low doesn't engage. I hear the clunk noise in 4 low and the lights work properly on the dash but no front traction. Could it be due for a rebuild or simply a little low on fluid? Just thought I'd ask while on the subject and you seem to know a few things about the AUTOTRAC T-case. Thanks and let me know if you can.

chevroletmb · November 17, 2004

well if u can hear it go into 4 low the front diff actuator might be bad

but the best starting point for an autotrak is scanning for codes

sub5 · November 17, 2004

Good point, especially that my check engine light has gone on & off lately. But the 4w auto does work well which tells me the diff functions. But I'll hook up my laptop to it and scan for codes sometime this week. Thanks.