Offroad Trailblazers and Envoys

Auto mode (4wd)

Trailblazer and Envoy related, but not off-road related...

by jrivs4x4tb » Thu Feb 04, 2016 3:02 am

Quick question, on trailblazers when you select the auto mode on the 4wd selector, does it keep the disconnect engaged? Also what are the benefits of using auto and not 4hi? And am u safe to leave it in auto all the time? Guessing it would act like an AWD vehicle.

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by jrivs4x4tb » Thu Feb 04, 2016 3:03 am

I*

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by v7guy » Thu Feb 04, 2016 3:18 am

It does keep the disconnect engaged.

Automatically letting it engage 4WD is hard on the system.

IIRC The only beneficial time we've been able to come up with is when pulling out of a slippery spot to dry pavement.
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by TBYODA » Thu Feb 04, 2016 2:36 pm

From what I have read, when in auto there is constant ~ 5% load to the front wheels from transfer case. If you were to leave in auto all the time you will most likely prematurely wear your transfer case. AWD models have a different transfer case than ours so this is not a issue. Adding to what Jason stated one issue is the possibility of shock loading the transfer case when the rear wheels lose traction. When the loss of traction is detected more load is applied to the front. In some cases the rear wheel slippage can be intermittent and thus the load is varied to the front. This is when the a high shock load can happen and possibly damaging the transfer case since ours is different internally then the AWD version.

I have found from experimentation it is to risky to use auto at all because of this varying load to the front. One in drivability and two possible transfer case damage.
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by jrivs4x4tb » Fri Feb 05, 2016 2:58 am

OK, thanks for all the input. I only ask because even after I fully rebuilt my front wheel disconnect, its sometimes refuses to engage in cold weather. And given all the snow here in Colorado I would like the disconnect to stay engaged. Just found a great solution though.
I will put the truck in 4hi, after it successfully engages , I will unplug the connection to the solenoid on the disconnect and leave it in the engaged position , I have an old solenoid that is worn and will plug that one in and zip tie it to the frame.
This will hold up until I find the time to rebuild the disconnect with the AWD sleeve.

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by KielTb » Thu Feb 18, 2016 8:52 pm

Is it possible, (or safe??) To leave the front engaged 24/7? With the open front differential it shouldn't bind under turning and will theoretically just spin the front drives haft and the disengaged transfer case? Or would that ruin the transfer case being free spun by the front wheels :(
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by Jrgunn5150 » Thu Feb 18, 2016 8:54 pm

KielTb wrote:Is it possible, (or safe??) To leave the front engaged 24/7? With the open front differential it shouldn't bind under turning and will theoretically just spin the front drives haft and the disengaged transfer case? Or would that ruin the transfer case being free spun by the front wheels :(



Every single TJ, JK, XJ, and ZJ ever built is running around with the front axle engaged at all time's. It's fine.
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by KielTb » Thu Feb 18, 2016 9:02 pm

Is there any difference in wear pattern with leaving the disconnect in the engaged position? I would assume at least to some degree the bearings in the disconnect would wear from the spinning intermediate shaft and cv
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by Jrgunn5150 » Thu Feb 18, 2016 9:28 pm

KielTb wrote:Is there any difference in wear pattern with leaving the disconnect in the engaged position? I would assume at least to some degree the bearings in the disconnect would wear from the spinning intermediate shaft and cv



I'm sure you are correct, but it's insignificant. I mean, the AWD varieties run these parts from the factory and don't seem to fail at a higher rate.
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by Shdwdrgn » Sat Mar 05, 2016 1:04 am

I realize I'm a little late to the party, but just wondering if you repacked with full synthetic grease when you rebuilt your disconnect? I had a lot of intermittent problems with mine engaging, and the last year before my rebuild I had serious doubts if it was engaging at all... but in the last two years since I did mine (which was just a complete cleaning, new bearings, and new grease), I haven't had a single problem.
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by v7guy » Sat Mar 05, 2016 1:42 pm

There's also the possibility there's so much grease in there it has trouble moving cause it's packed with too much.
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