[O.G.]

I don't know HOW many times I've read this sticky, and it's definitely in my eventual plans for my truck, but as usual, more questions. Is an AWD front diff more of a limited slip design, or is there another reason to use the AWD diff in the conversion? Right now my 95 has the front axle shafts removed because it's dropped so much, but I'll be putting them back in before winter. If the AWD diff is LSD, then I may use my 4wd case until I can afford the rest of the parts, and use it like "selectable AWD", if the AWD front diff can safely be driven without full time power to it. I think that makes sense, but if any questions, I'll try to clarify.

Can someone shed some light on this question since I have the same question. I just picked up a 1993 blazer 4x4 with the Tahoe option and 3.42 LSD's. I also picked up an awd from a 1993 Bravada. I will still need the front shaft and passenger side axle tube. Anything I'm missing?

 

[AWD V8]

The front diffs, AWD or 4wd are open diffs, no LSD.

The 4wd diff uses a coupler on the passenger side axle shaft that disengages when in 2wd to reduce the drag of the ring and pinion for improved performance and reduced fuel consumption.

When shifted into 4wd, the transfer case sends vacuum to the servo for the axle couple when the shift into 4wd is completed in the transfer case. So the transfer case completes the shift into 4wd, THEN vacuum is sent to the servo for the axle coupler. Once the axle coupler has engaged the shift into 4wd is complete.

The AWD diff has no axle coupler, it is under power at all times.

AWD transfer case vs. 4wd transfer case.

The 4wd transfer case always sends power to the rear diff. Only when in 4wd does the transfer case send power to the front diff.
The 4wd transfer case, in 4wd, locks the front and rear drive shafts together, NO slippage.

The AWD transfer case sends power to both drive shafts at all times,... BUT, their is a viscous couple inside the transfer case that splits the power, front and rear. This works similar to a limited slip diff. In other words, if one end has slippage, power is still sent to the other end. If both ends have traction then power is split equally front and rear.

Now, when you replace your 4wd transfer case with an AWD transfer case the front drive MUST be connected at all times. If you do not have the axle coupler connected, or have no front drive shaft, the viscous coupler will be slipping inside as some power is lost to the front end. The viscous couple has provision in it's design to accommodate some slippage for cornering and tire wear. It is NOT designed to slip continuously! It will overheat and the thin plates inside will distort from the heat and warp. Because of how close they must run to each other they will contact each other and the unit will seize.

Some people don't believe me that the AWD transfer case has slippage. A real life example: When building my truck at one point I was waiting for my front driveshaft to be shortened. I needed to run an errand so I took my truck, no front driveshaft installed. I parked the truck on a bit of an incline, put it in Park and left it for 5 minutes. When I returned the truck had creeped down the incline and was nosed into a wall. The transfer case DOES slip, but very slowly.

As far as what front diff to use with an AWD transfer case, I recommend an AWD diff, like an Astro or Bravada. (they are exactly the same diff, you can use either)

I believe the 4wd diff is not designed to run continuously or at higher speeds. We already have issues on our trucks with the coupler wearing.

I hope that answers your questions.

 

[O.G.]

Thanks it definitely does. The one I picked up has 170,000 miles on it. Are there any rebuild kits or upgrade kits for these transfer cases or OEM replace my parts are sufficient?

 

[AWD V8]

I couldn't tell you, I've never needed to open one up.

 

[Nviousraver]

I just read this and I see you say you can use a 1st gen Bravada transfer case. I have found one with the whole driveline intact but it says smarttrak so would that mean its an electonic transfer case or will it work. Thanks in advance

 

[AWD V8]

An electronic transfer case would require a computer to control it. And, is the smarttrak a real AWD transfer case, or is it auto 4wd? I don't know for sure.

 

[Nviousraver]

Been reading on this for an hour or so and it sounds like the 1st gen bravadas had the 4472 in them, since Ive never done this Im assuming the easiest way to tell is look for wires coming out of transfer case?

 

[ZekeBB]

Great info. Thanks a ton for this. I had never had it cross my mind to awd an s10 until a few months ago. Actually never knew it was a thing lol but looks like a simple enough conversion provided you do it right with the right parts. Bravadas are plentiful out in my area so should be able to avoid messing with the drive shaft at all. This may be my next project then. Awd coupled to a 5.3 ls motor. And if people are doing 10 second runs then I highly doubt the system will have trouble holding up to anything I do.

 

[TokoDragon]

Great information AWD V8! Thank you

- I might be doing this to my 92 4.3L 4x4 5-speed. (if I do it'll probably end up being V8 and auto)

I tried to find more information on the transfer case offered in the bravada, pretty sure Olds used the name "Smart trak" for all bravadas the first gens used the borg warner 4472 non-electric. (Not sure what they used 95-97) then 98+ is the electronic NV136. It stays in 2wd and switches to AWD when a slip is detected- the driver has no control over the switch. Similar but not the same as Auto-trak which switches in and out of 2wd and 4wd (50/50 split no slippage) and it also has 4hi and 4lo. NV236

 

[Back_N_Black]

Let me see if i got this straight. Also questions about a part of the article I wasnt clear on...


NEEDED:
Non electric transfer case from a Bravada or Astro/Safari. I will probably get mine from a Astro/Safari


The 1372 with a 27 spline rear output and the 4472 with a 32 spline rear output. <- does it matter which one I use?


Maybe mod the crossmember by dropping the mount 1/2". My Luck, go ahead and count on it.


Notch the Bolt on transfer case for easy removal.


Match slip yolks to transfer case, factory driveshaft should work.


Here's where I'm confused. So let me see if I got this right; Remove the front differential and install Astro RIGHT side (only right side?if so why?) axle and tube. Swap the 4x4 pinion flange over to awd because they are different. If the donnor front differential ratio is the same as the rear just swap the whole differential.


"The early Astro uses bolt on front axle shafts and later used slip in shafts, I don't know the years, but you can easily swap the parts over. The 4x4 uses 6 bolt flanges until '97 and slip in CV joints 98+. You can swap the later slip in diff if you use the slip in axle shafts. You just have to match bolt on with bolt on, and slip in with skip in"


^ Wut? Is that only important if your using astro stuff? I already own a 98+ Bravada. Does it make sense to steal the differential and axle tube from it and use the existing Cv axles?


When installing the front differential cut the lower mount for clearance. Is this required? If so why? Need more clearance with the Awd pinion flange?


Front driveshaft: AWD Bravada shaft = Good. AWD Safari/Astro = Bad, needs shortened.


Remove 4wd bs


Check and reroute fuel lines if necessary.


Is that about it?

 

[TokoDragon]

alright I will try to help ya ou back-n-black if you can answer the questions I have lol

You are correct, 1372 vs 4472 are same internals but 4472 is a 32 spline rear, and 4.25'' front flange. 1372 is 27 spline and 3.5'' flange. The 1372 came in (most) GMC Syclones, and Astro vans and the 4472 was in Typhoons and Bravadas (I think some bravadas had 1372 as well??) The is with first gen stuff, I think your 1998 bravada would have a 31 spline? or which ever the 2nd gen s-series used.

The 1372 might be less likely to need the trans crossmember modified.

I've never notched the mount to remove the 3 differentials I removed.

And the next question is where I'm f-ing confused too.

I have a 1993 astro van 1372 BW, it has a 3.5'' flange, and I'm using a 1998+ ZR2 front differential that has the standard pinion yoke. I tried grabbing a 1998+ Bravada flange but they also use the standard yoke. (and t-case flange appears to be 4.25") Then I found a 1998 astro van it uses flanges but they are larger (listed as 4.5'' flange?)

So I don't know where to get a flange to bolt to my ZR2 front differential so I can find a drive-shaft that fits the 2 together. (checked all local junkyards and didn't have a first gen bravada or astro 1997 or older)

Could I swap to the 1998 flanges on both ends and shorten it's driveshaft? (1998 astro is np136 tcase)

"The early Astro uses bolt on front axle shafts and later used slip in shafts, I don't know the years, but you can easily swap the parts over. The 4x4 uses 6 bolt flanges until '97 and slip in CV joints 98+. You can swap the later slip in diff if you use the slip in axle shafts. You just have to match bolt on with bolt on, and slip in with skip in"


^ Wut? Is that only important if your using astro stuff? I already own a 98+ Bravada. Does it make sense to steal the differential and axle tube from it and use the existing CV axles?

The next question is concerning different generations of front differential. up until 1996 or so you had to bolt CV axles in 97+ was slip in, so since you have a 98+ bravada it is slip in and it uses a NP136 t-case

SO since your bravada is 1998+ your front differential will also have a standard pinion yoke and the 1372/4472 t-cases use a pinion flange you are probably in the same boat as me, you'll need to find a pinion flange from a 1990-1996 bravada to bolt onto your front differential and use a 1990-1996 front drive shaft.

If anyone has 1, or can grab 1 at their local junkyard easily I will gladly pay! I want this truck done and no luck locally or online!

 

[TokoDragon]

GM26044459

appears to be the correct AWD pinion flange to fit the GM 7.25 front differential, BUT can't see anywhere if it is meant to work with for 3.5" or 4.25" or even 4.5" transfer case pinion flange setups.

My transfer case came out of a 93 astro but is a 3.5" output flange.

Also seen some front drive shafts with a CV listed to fit- but can tell my transfer case did not use a CV style shaft.

VS

 

[mog-10]

I plan to pick up a 1996 Bravada on Monday to pillage it of its transfer case ,trans adapter, crossmember, front - rear drive shafts and front diff for my 1998 Gmc envoy.

 

[TokoDragon]

Update:


I finished my AWD conversion- the trick is once you pick up 1 component of the AWD you really need to stick to that vehicle because the pinion flanges varied by make/model and year. I had a hard time finding a 4472 transfer case and when I finally did it was from an early Astro van which uses the largest shaft and pinion flanges of any of the other S-series compatible AWD. It required hacking the trans mount off of the cross member and lowering it just about as far as it would go, I can maybe slide a sheet of paper between the tail shaft and frame brace and the front drive shaft was a big mess. I had to use an Astro shaft to fit the flanges and it was too long so I had to suck it up and spend about $400 bucks to have all my shafts rebuilt shorter (2 piece rear shaft included in that price due to swapping rear axle, had I kept the 7.5 I may have been able to use stock unmodified rear shafts) I had to put the jack under the truck and smash the floor up for the front shaft as well. The 1 + to using the astro 4472 is it had a 27 spline output which is what 1st gen S10s use. (although swapping to a 32 spline driveshaft isnt hard)

I used a 2nd gen iron cast front differential but fortunately when it comes to the front differential it's all compatible across the board. So I found a 98+ bravada and grabbed the solid shaft for a slip-in style Differential then I grabbed a big pinion flange from a 1990 Astro van for the front differential and it bolted up no issues. (well besides the fact there is hardly a pinky finger's worth of room between it and the bell-housing.)


If you want to this swap to be easy and cheap you need to find a 1990-1996 Bravada the shafts are the right length, smaller, and use the smaller flanges and the t-case is the 4472 with 32 spline output. Also grab the trans crossmember and save yourself some cutting/welding.


But I'm glad I finished the conversion the AWD was worth all the headache! Eastern Idaho had to toughest winter in 2 decades and this AWD truck romped right through it with a smile! In dry weather it's also fun to throw it through the corners at full throttle with traction to spare.

I wish I could afford some 18x9.5 corvette wheels at all 4 corners- I've been bit by the traction bug.

 

[AWD V8]

^^^ looks good. Traction is a good feeling!

Yes it is good to use as many of the AWD components from the same vehicle. I bought a 1992 AWD Astro for my first conversion. A Bravada would have been even better, but I've only ever seen one up here. I swapped the Astro transfer case in and front diff. I had to have the front drive shaft shortened but the flanges were all the correct size of course. This is where the Bravada front drive shaft would be a simple bolt in. The output splines on the transfer cases come in 2 sizes. On my second AWD I just swapped the slip yoke and was good to go.

Now you need a turbo or V8 to take advantage of that traction.

 

[TokoDragon]

I was kicking myself while pulling the parts out of the astro van- a couple months earlier my friend and I ran across a 91-93 bravada in the junkyard and all we did was drag the nice dash out of it and considered grabbing the cladding never thought about AWD then.

The awd truck also has coilover conversion and big sway bars front/rear and a few energy suspension pieces. The brakes feel about as good as Id expect a corvette or similar with the 2-piston calliper full-size MC, rear disc, and powerstop rotors/pads.

I really want rack and pinion and an LS engine. (even an LV3, the new mostly aluminium 4.3L) If you check out the 4x4 droppin' section there is a build adapting a rear mounted cts-v/corvette t56 transmission into an awd setup. That's about as ideal as you can get to make an s-series handle.


I've pushed my s10 pretty hard, but not hard enough to cause a slide yet (on pavement) I haven't felt any understeer, if anything I think it'll oversteer when pushed past the limit. On the snow it was a little counter intuitive when the truck was sliding to tap the gas but usually when I did the front wheels would grab and pull the truck out of the slide.

 

[LilJohn]

For the front, is there a reason to swap the Bravado/Astros tube if a plate is made to cover coupler shift hole?


Also, will the following shaft work?
https://www.ebay.com/itm/12479125-F...lazer-Envoy/111568070360?ssPageName=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649


I'm getting ready to rebuild the front and figure swapping the shaft would be easy at this time.

 

[AWD V8]

You can use a 4x4 tube, the axle disconnect is the issue. You can either swap in an AWD shaft or make the axle disconnect engaged full-time.

The axle in that link does not describe the applicable years. Their are first and second generation Envoy and they are totally different animals. Doesn't look like an AWD axle shaft to me.

 

[LilJohn]

You can use a 4x4 tube, the axle disconnect is the issue. You can either swap in an AWD shaft or make the axle disconnect engaged full-time.

The axle in that link does not describe the applicable years. Their are first and second generation Envoy and they are totally different animals. Doesn't look like an AWD axle shaft to me.

Thanks for confirming that the tube swap part of it is just to seal up the axle disconnect hole.

And thank you for confirming that I was looking at the wrong shaft.

 

[BigEd51]

Let's start by stating that I am not the be all end all of AWD conversions. I did 3 of my own trucks and I can only comment on how my conversions went but not if "this" transfer case will work in whatever truck you have.

AWD what is it and why would I be interested?
An All Wheel Drive conversion is main done to increase the traction of our trucks. Basically we start with a 4wd or 4x4 truck and swap in an AWD transfer case and change some stuff on the front end. GM did this with the Typhoon & Syclones, and stuck a turbo on it just for fun. These turbo trucks really hustle and without the extra traction would be a handful. Even those of us with a 2wd or a 4wd IN 2wd, merging into traffic on wet pavement can be a frustrating experience.

Pushing a 2wd truck to the limit is usually reached early as the rear wheels break loose. This of course means that the truck has reached the limit of cornering as you can't push it any harder into the corner without totally spinning out. This is where AWD becomes more than just a straight line modification. With the extra traction available, a front tire must also break loose before the truck will also lose traction in the rear. This means that corners can be taken faster for those of you interested in track or auto-x, not to encourage spirited driving on the street

So this began with my 89 4wd Jimmy. I wanted a simple no frills AWD conversion, just like the Typhoon. At the time I had planned a V8 swap, hence the AWD V8 moniker. I chose to use an AWD transfer case out of an Astro/Safari van. The early ones are non-electronic, I don't know when they went to electronic, about '95 but someone can correct me. The non-electronic transfer case only has a VSS sensor on it, no other wires or sensors. Bravadas work too, we just have more AWD vans up here than Bravadas. Different years and whether van or Bravada, you have 2 transfer case available. The 1372 with a 27 spline rear output and the 4472 with a 32 spline rear output.

As far as I know any AWD of these transfer cases will fit any auto or manual in our trucks. IF you are doing a V8 swap and are interested in AWD but only want a manual transmission, you will need to consider how your transmission will hold up to a V8 with added traction. There is a T56 conversion to a 4wd/AWD transfer case but it is ultra expensive, several thousand last I heard.

When you remove your 4wd transfer case and compare it to the AWD transfer case you will see that the coupler shaft is longer than the AWD's, don't worry it will fit fine.

4x4 transfer case

AWD transfer case

Don't worry about the difference in depth, the AWD transmission output shaft is the same as the 4x4 transmission.

Again, 4x4 transfer case top, AWD transfer case below.

Swapping in the AWD transfer case is a straight forward bolt up to the transmission, but because the output of the transfer case is clocked higher it can hit the floor or fuel lines.

Note: If you are using a transmission from a 4x4, you need to know that the transfer case shifter that you removed, was bolted to the intermediate housing between the transmission and the transfer case. These bolt holes go right into the housing leaving an opening for dirt & water to get in, and oil to get out. I applied sealer to the bolts and screwed the bolts back in. Not needed with push button 4wd trucks.

Once you have your AWD transfer case installed you can remove and plug the vacuum lines.

Tip for the 4wd guys with a persistent transmission oil leak on trucks with a floor mounted transfer case lever, these bolts come loose and will leak oil, remove the bolts one at time and seal them.

Next post, modding the transmission mount.

sticky please


and thanks AWD! thats alota typing lol, much appreciated, this has been needed info on here for a long time

I have a 2000 s10 p'upw/4.3.Could I change out my frt diff for a Bravada orAstro and use my oem transfer case? How would that work?