Strengthened S10 IFS

There are several areas that can be upgraded from a stock S10. This thread will mention two specific improvments to the front drivetrain.

Differential housing. The factory setup for the front differential housing material is cast aluminum. This is light weight but under heavy load can cause deflection of the pinion. Trucks that came stock with a manual transmission also came with a cast iron front differential. This housing is substantially stronger than the aluminum housing and can be swapped in with no modifications (assuming both diffs have 3.73:1 gear ratios).

Axle tube. One of the common complaints from S10 owners is that the four wheel drive stopped working. These vehicles are equipped with a two-stage shifting process. First the transfer case shifts into 4HI (or 4LO). That opperates a vacuum switch that sends vacuum to the front of the truck under the battery tray where a module uses the vacuum to pull on a cable to engage small sliding gears on the right side axle tube. Any one of these things can fail (switch fails, vacuum loss, vacuum diafram fails on the module, cable binds, gears bind or are stripped). There is one S10 based vehicle that omits all of this... the Oldsmobile Bravada. Because it is all wheel drive, there is no reason to have the front axle dis-engaged. This is plug-n-play for the S10s. This also eliminates a weak point in the axle (the sliding gears only engage about 1/8" - 1/4" of spline.

Steve

Some of you might be wondering: What is the Bravada shaft mod that he keeps talking about? This is a more detailed description of the axle tube mod listed above.

From the factory, the S10s (and the ZR2s are no different in this respect) came with a two-piece front axle shaft. This prevented wear and tear on the front ring/pinion and front drive shaft. This was achieved by an axle disconnect in the right side axle tube.

Description of operation from the factory:
When the 4WD is desired, the driver pushes a button. This sends a signal to the TCCM (transfer case control module) in the right kick panel. The TCCM then sends a signal to the shift motor mounted on the transfer case to shift into the desired range (2hi, 4hi or 4lo). When the transfer case shifts, a vacuum switch on the top of the transfer case allows engine vacuum to a diaphragm mounted under the battery tray. This diaphragm pulls on a cable that slides a splined collar over the two axle pieces in the RH axle tube.

If everything works and is in good condition (selection switch, TCCM, shift motor, vacuum switch, vacuum hoses, vacuum diaphragm, cable, collar/axle splines) then you get power to the front axle.

The front axle shaft from a Oldsmobile Bravada (S10 platform) is AWD and has no need for a front axle disconnect. GM made a one piece axle shaft and appropriate housing tube for this application. This eliminates everything in green above. This setup is also stronger.

This is off the truck (obviously) and the end you see would be tucked into the differential housing, the cable would be pulling on the thing on the top (pulling to our left):
2WD mode


4WD mode


Notice in the 2WD picture that the splines are worn down on the axle side. This was from attempting to engage 4WD on while moving. If the front drive shaft isn't moving, then the spider gear in the differential are. If one is traveling forward at 30 mph, the outside of the shown axle shaft is spinning at that speed, and the inside would be spinning BACKWARDS at the same speed. Add a small vacuum leak (at the switch in the transfer case) and this is what you get.

I have noticed no increase in fuel consumption nor increased parts wear due to this mod. It is functioning exactly as it would in a stock Bravada.

Steve

Man...this looks like a great oppertunity to get rid of electronics and vacuum actuations in favor of some sort of cable drive. I don't know what the rest of this assembly looks like but the basic functions here would suggest a simple pull cable or the like would give you control of 2WD/4WD functions without the need for added complication. Just my $0.001674.

Spence

That would be a similar setup as a 4x4posi lock using cable to engage it. I dont know much about IFS systems at all.

Those simple pull cables run upwards of $200. Not worth it in my opinion. I fixed my issue with 3 zipties (temporary until I change it to a solid shaft). Steve fixed his issue by removing the 2 piece problem and replacing the issue with a stronger solid shaft & tube.

EDIT:
For a 88 Comanche with a HP30 & CAD, $249.39:
http://www.napaonline.com/Catalog/Result.aspx?Ntt%3dposi%2block%26Ntk%3dKeyword%26Nty%3d1%26N%3d599001%2b101988%2b50038%2b2038006

http://store.hamiltonmarine.com/browse.cfm/control-cable-x-treme-6-series-4300cc-150813/4,49027.html

This is what I had in mind. No, it isn't free, but it could make for a viable option with a little fabrication. The end result would be far more robust and reliable than the vacuum system, and having the option of disengaging the 4WD system especially given current fuel prices is worth consideration...

I have done this on four ZR2s now and have noticed no increase in fuel consumption or wear.

booth9c1ss wrote:I have done this on four ZR2s now and have noticed no increase in fuel consumption or wear.

When I permanently "locked" in my CAD on the Comanche, no decrease in mpg's were noticeable. Peeps on CC said they experienced it, but not I. I enjoyed being able to pull lever and go and not hafta worry 'bout if the vac system was working or not.

Flipside; I want manual hubs on the Taco for longevity of the CV shafts and increase in MPG's. I DID notice a difference on the Row-day-oh when I installed Superwinch manual hubs on it. Plus when I snapped a shaft, I just unlocked that side and kept wheelin' AND drove it home.

Steve, the piece of mind is definitely worth it. Especially after experiencing it not working properly at 50 MPH.....