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2005 gmc envoy_slt
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Discussion Starter · #1 ·
Has anyone by-passed the disconnect fork? Ok here is my thinking. The following is referring to the exploded view I have seen posted here on the 4WD front axle. Looking at the parts list for the front axle disconnect assembly # 56 (4x4 actuator case). If you eliminate the fork and swap out the outer gear # 11, sleeve # 12, washer # 13 and inner gear # 14 and you replace it with the sleeve # 5 from the front axle assembly # 57 (AWD case) you have eliminated the disconnect. You can still use the electric actuator hooked up so the computer would think it is engaging & disengaging the 4WD and no 4x4 service light. I don't see the BIG benefit of the disconnect, it only disconnects one axle and the carrier and or spider gears are still turning, what am I missing? The trade off is what, maybe 1 MPG and a little more wear? Just a thought to eliminate the fork from breaking just when you need it. Am I crazy for even thinking of this? :crazy: Jim
 

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You're thinking correctly. No downside at all to that plan and I can't even see why the mileage would go down. Have to think more about why they even bothered to put it in. :undecided
 

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2006 chevy trailblazer_ls
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Only thing I can think of is a little extra drag from having to spin up the entire differential/pinion, the prop shaft between the TC and front diff, and all the associated bearings and seals.

Do the gains reaped from having the disconnect really warrant the complexity? I just know GM engineers (im related to one) fight tooth-and-nail for every bit of fuel efficiency they can get.

Would love to hear the results.:thumbsup::thumbsup:
 

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The $200-700 saved (DIY cost-dealer's price) on not having to replace parts of the disconnect can pay for a lot of gas. Assuming it stays well-greased and you don't lose a bearing over the years. ;) The inexperienced designers wrongly assumed their design would last the life of the vehicle.

Since the side gear is already driven by the non-disconnected driver's side CV shaft, and that spins the spider gears which drives the intermediate shaft backwards, there's already a bunch of moving parts in the diff that make it risky to run dry. A lot of owners ask if they can safely get around in 2WD mode even if their dry diff makes grinding noises in 4WD. And sadly, it's not a good workaround.

Too bad we didn't have disconnectable hubs at the OUTBOARD side of the CV shafts like other vehicles. I'd even take MANUAL hubs.

 

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2003 chevy trailblazer_lt
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wait just had a thought... if we kept it connected... wouldnt we still get the crop hopping when turning.. the rear wheels are powering but the front wheel would be locked together and want to turn at the same speed as each other...
 

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wait just had a thought... if we kept it connected... wouldnt we still get the crop hopping when turning.. the rear wheels are powering but the front wheel would be locked together and want to turn at the same speed as each other...
No.

It's essentially the same situation as your rear axle with the transmission in neutral. The wheels can rotate at whatever speed they like with any difference being made up by the diff carrier.
 

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Without taking the time to look at the transfer case/TCCM drawings, let me toss out this for consideration.

As we all know, the AWD only trucks do not have a disconnect on the front axle. They also use a different transfer case.

When our trucks (4WD) are asked to shift into one of the 4WD positions, the shift motor moves into it's required gear position.
Once there, a signal is sent, from the TCCM, to engage the front axle.
A full engagement signal is returned from the front axle assembly to the TCCM.
Once this signal is received, the TCCM signals the shift motor (in the transfer case) to lock.

Disrupting this lock signal could cause transfer case failure.
 

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Ray, you could dangle the front axle actuator in midair (tywrapped to something under there) and it would return the proper feedback signal. And then you'd just have to put a blank-up plate over the actuator hole in the housing. There are also ways to remove the actuator's final drive gear after the feedback finger jackscrew and simply disable the fork-pushing part of the actuator while leaving it electrically unmodified.
 

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Bill, I like the idea of separating mechanical and electrical functions. Mechanically engaged, electrically disengaged. :thumbsup:
 

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2005 gmc envoy_slt
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Discussion Starter · #12 ·
Thanks all for the input, Guinea pig or not I have ordered the parts and feel this change should work just fine, ordered through the Compnine web site, hope that works. My older 4X4's didn't have axle disconnects and did not crop hop as you say during a tight turn when the transfer case was disengaged. I will bolt the electric actuator where it belongs to have it do nothing but move air and return the proper signals. Once I get a break in the weather I will let you know how I made out. Jim
 

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Any updates?
 

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Thanks all for the input, Guinea pig or not I have ordered the parts and feel this change should work just fine, ordered through the Compnine web site, hope that works. My older 4X4's didn't have axle disconnects and did not crop hop as you say during a tight turn when the transfer case was disengaged. I will bolt the electric actuator where it belongs to have it do nothing but move air and return the proper signals. Once I get a break in the weather I will let you know how I made out. Jim
I am not quite sure this is a good idea. Roadie may know more about what I am about to say. With the disconnect always working you are spinning the Pinion bearings, u-joints and the output of the front transfer case bearings. However you are also spinning a lot of other items in the transfer case and might cause internal failure of clutches, bearings etc. You still have the output bearing to wheel problem of it drying out and the bearing seizing. It would be like driving the tb with it in a4wd 100 % of the time. Except that the sensors that control the clutches will be off and that might cause a sensor problem. Your older 4x4 had a real transfer case on a joy stick and when it was off it was off. You should also have had hubs to disconnect the wheel from the diff. output shafts.
my :m2:
 

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I thought about it a bit, and since there are full-time AWD versions of the vehicle, most of the issues about seals aren't so much of a worry. Or else we'd be hearing from a lot more AWD owners about them failing with high mileage.

The TC clutches should be spinning at the same RPM unless there's wheel slippage, so I don't think that's a risk.

So what's left that different is the low range feature, which for us is a planetary gear set on the shaft closest to the transmission. They shold be in a TC fluid bath all the time, so that's a low risk, IMO.

In 2HI mode the encoder motor goes to a park position that reduces the clutch friction to a value lower than the "ready" position it's in for A4WD.

Personally, I think it's a minor risk compared to all the other things we do while offroading. But the moving collar isn't the only thing in this assembly that's poorly designed - the lubrication of the bearings is also poor, which is why the AWD SS vehicles are also damaging their assemblies and Dorman is interested in giving THEM a solution as well.
 

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Personally, I think it's a minor risk compared to all the other things we do while offroading. But the moving collar isn't the only thing in this assembly that's poorly designed - the lubrication of the bearings is also poor, which is why the AWD SS vehicles are also damaging their assemblies and Dorman is interested in giving THEM a solution as well.
I agree Bill, this is no different than leaving the selector in the AWD position.

Just a thought to eliminate the fork from breaking just when you need it. Am I crazy for even thinking of this? :crazy: Jim
I understand your thoughts here, but maybe just keeping spare parts for the disconnect (maybe a complete assembly) would be a simpler approach. :undecided
 

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Discussion Starter · #18 ·
Update: I am waiting for parts from Compnine, I ordered parts on Jan 26th and here it is Feb 5th. The order was pending for a week and now it says processing, guess that takes a week and then maybe another week for shipping? Sorry, I lost it for a minute. :hissy: Anyways the way I look at it is, when the driver's side wheel is turning it is turning the spider gears and will likely be turning the carrier which will be turning the front drive shaft so all of it is moving. Honestly from a wear on parts prospective I would rather see the carrier and pinion bearings spinning then the spider gears constantly turning. I have rebuilt many differentials and when abused the spiders take most of the punishment and fails first. I agree the older transfer cases would mechanically disengage and most trucks had front hub disconnects but not all, I did add disconnects after rebuilding a few front drive shafts. FYI, I have towed the Envoy behind a motor home for over 40,000 miles for upward of 700 miles nonstop and 1,700 miles before restarting the engine without a problem, granted the TC was in neutral but stuff was moving, I believe the TC can handle the shaft turning some. I did get a e-mail from Compnine and do expect the parts someday, when that day comes I will let you know how it went. BTW, I have hub bearings and shafts to put in while I got her apart.
 

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Here's my input on this whole situation. First I did some scanning when i was driving here a couple days ago your front driveshaft is spinning when you are going down the road in 2hi. The average difference in speed was between 300 and 400 rpm from the front to the rear shaft, Example Rear shaft 2000 rpm front shaft 1700 rpms. My scanner show the actuall difference in rpm's.

Second the fulltime awd vehicls use a housing similar to our splined disconnect housing but it don't disconnect so if you were to ditch the splined disconnect idea Maype you could install one of the units off a awd or even just order the internals and install them in to your housing and like bill said once before just leave the actuator hanging there so the tccm still sees it and thinks it's working. You could maybe even leave it in the side of the housing.
One other thing like bill said is it puts your t-case into a park position keeping the clutches farther away from each other unlike some people who run around in a4wd from november to april causing there clutches to be in super close contact and engaging quite often due to the programming in the tccm. With the disconnect permanently locked however it's done the propshaft would always be spinning the same speed as the internals and the clutches would be kept farther apart reducing wear on the clutches POSSIBLY.
Hope all that makes sense.

I'm open to any thoughts or comments or critisism.

Out of curiosity what parts did you order jjmoore you never really said.
 

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After studying the diagram on the compnine website and comparing some part numbers it looks like outer half of the housing uses a different part number but that might be just for the actuator hole. You could get away with spending about 130 bucks for parts IF you can reuse your outer housing.

The only parts you would need to order are 1,2,5 and 8 versus 1,2,11,12,14,8,17
of course this is all depending on how bad yours is.

 
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