short version; read the bold below

long version;
I've been reading a few how-to threads regarding this conversion and I have a few questions.

As I understand it, in order to shift into 4WD, the driveshaft needs to engage both the front differential and the transfer case

It seems the transfer case engagement can be converted to shift manually by removing the encoder motor and building a shift linkage up into the cabin. The differential engagement can be converted by use of a posi-lok or a home-made cable.

In one of the how-to's that I read, the guy who wrote it said he had done the manual transfer case conversion and had successfully driven around with transfer case engaged full time and then when encountering a need for more traction, he could press a button to engage the front differential.

My question is, if it's alright to drive with the transfer case engaged and manually shift the differential, would it work alright the other way around? Instead of having to rig up a posi-lok to engage the front diff, would it be possible (and/or safe) to lock the actuator cable position so that the differential is always engaged? Then, in order to shift from 2HI to 4HI, you would only need to shift the transfer case.

It seems like it would work but since I still don't have a great grasp on how the transfer case works (or the rest of the 4x4 system for that matter), there could be some problem that I've overlooked.

Thanks in advance

 

Hi,
due my bad encoder motor and TCCM my gearbox is locked in 4HI. I just converted the front differential to manual shift and put in 4WD or not.
In the gearbox the gears are the same in 2HI and 4HI, so there's no difference for the gearbox between 2and 4WD.
But you can't let the 4WD engaged when you drive on the street, it puts a lot of stress on your drivetrain...

 

But what if it was your front differential that was locked. Will the truck work alright if the front diff is engaged but the transfer case (gearbox) is in 2HI?

 

Hi,
why should it be my front diff?

If your front diff is engaged and the gearbox is in 2HI, its exactly the same then 4HI... There's no difference in the gears between 2HI and 4HI...

The gearbox shifts between LO and HI and the front diff between 2WD and 4WD. When you have both manually, you can also shift in 2LO.

 

I was curious about the front diff because from what little research I've done on the subject, it seems like converting the transfer case to a manual shift is much simpler than converting the front diff. I am hoping to get rid of all vacuum controls and go with physical cables and linkages. If I can lock the actuator cable so that the front diff is always engaged, then I would only have to convert the transfer case.

There has to be some difference between 2HI and 4HI in the transfer case because the motor has three positions, not just a HI and LO.

thanks

 

It just won't work with the front diff always engaged? Put your Blazer in 4WD and drive on the street and you'll see why...

The front diff conversion is not as hard as it seems, you hast have to lenghten the actuator cable and put it in the cab...

Yes there are three positions of shift in the transfer case. Ok, let's see how I can explain that in my poor english...
The front diff that engages the front axle (4WD) is actuated with vacuum. The vacuum is provided by the engine and switched by the transfer case. That switch is engaged by the encoder motor. So, here are the three positions:
2HI: Nothing is engaged
4HI: the encoder motor moves one position, the vacuum switch is engaged
4LO: the vacuum switch keeps beeing engaged, the gears move to LO

 

Just so SFA... then eliminate all the 4x4 issues...lol

 

Maybe next year...

But the transfercase won't change with Sfa, so the problems remain...

 

How exactly did you convert your front differential? Did you lengthen the actuator cable into the cab or is it still vacuum controlled?

Also, you're english is very good and easier to understand than a lot of people that live here.

 

Hi,
it`s still vacuum controlled, because the actuator looks still pretty good. But I think I`ll add a hood cable to it and put it in the cab someday, so everything is manual...

Will start tomorrow morning, so check for updates...