Well, I picked this truck up a month or two ago and starting to look into power mods for it. Of course....

I've never built a muscle truck with 4 wheel drive so i'm not sure on the sturdyness of the extra componants.

what can the stock front diff and tranfer case handle power wise? I know the stock 4L60E will for sure be swapped eventually for a 4L80E along with the needed items to make it work, but what about the transfer case? Is there a stronger one to go with? Or is the stocker fine as long as its in good shape and works properly. It IS an Auto-trac BTW.

Also how about the rear end? Stock posi 3.73 gears. Whats the beefier alternitave that stays 6 lug?

I've seen some wicked trucks on here, but don't seem to see much mods pertaining to the parts I have in question. Hopefully that means the stock stuff will suffice for some good power.

 

There are several guys 500+rwhp and some over 600 through the front diff..

As for the rear end most seem to be holding up with a trutrac and stock shafts..You could find a 6lug 14b from an sss if you wan to upgrade..

 

Just as Andrew just said, there are plenty of folks pushing a good amount of power through their stock front differentials, transfer-cases and stock 10-bolts in 4WD applications. The 8.25” front differentials don’t seem to just explode under a good amount of power being run through them, but just can’t seem to hold a set of bearings worth a damn and is their major downfall. Even the CV axles seem to hold up decent, as long as the angles are good. The stock 10-bolt 8.625” rear differentials hold up pretty well in a 4WD/AWD application having the load split with the front axle, but I would still replace the G80 carrier, as it becomes the weak link. While the transfer-cases hold up fairly well under fairly high power, if I were swapping in a 4L80E, I would look for a transmission and transfer-case combo. The HD series trucks have comparable units as the 1500 series trucks, but with heavier duty components and would make for a stout drive-train. Making the swap to an 80E will also have you looking into drive-shafts, to which I would go ahead and purchase aftermarket units to further fortify your driveline. Also as Andrew said, if you happened across a 14-bolt 9.5” 6-lug rear axle, you would be pretty well set for all out torture.

While the little 8.25” front differential seems to get by alright in some pretty mean trucks, if you’re the fabricating type, swapping in a 9.25” front differential from a 2500/3500 series truck is possible, but not a bolt-in by any means and would be the finishing touch to a bullet proof drive-train or at least as bullet proof as you could get with an IFS front suspension. The other good thing about the 9.25” diff is you can get TruTrac or other type of traction aided carrier for the front, whereas there is nothing available for the 8.25” units due to their inherent weakness. By the way, the conversion is a pain enough that only a few have made the swap, but it sure would be cool with an E-locker in the front for track use!

 

Thats a hell of a deal then! I'll be sticking with the stock NP246 case and stock front diff. till i really start laying the power down.

And since you mention that the stock diff doesnt seem to keep bearings, i hear a squeel type noise on right hand turns and slightly while rolling down the road, but i have to be next to a wall or hiway divider to hear it. Which bearings are you talking about?

 

The side bearings of the carrier take a beating usually. What happens in a lot of the units is the adjustment retainer locks have their tabs break off allowing the pieces to back off and it’s down hill from there. Once metal starts floating around, usually the next item to go will be the pinion bearings. If you catch it reasonably early, just re-freshening the bearings will get you back in good shape, but if it’s allowed to go too long, the metal fragments will eventually destroy the spider gears and finally the ring and pinion gears.

Beings you just picked this truck up, I would do a pretty good examination and servicing to it. Take a good look at the wheel bearing hub assemblies, as they could be suspect considering the year model unless they have already been swapped somewhere down the road. Look at the axle seals for leaks at the inboard CV area. Check out the CV boots themselves for tears and grease seepage. Finally, when servicing the front differential, take a close look at the gear oil and the magnetic drain plug for evidence of a problem. Don’t get too worried if you see a small amount of glitter in the oil and a little hair on the drain plug, as just about all of these differentials will experience it, but instead look for fragments or excessive amounts of material floating around, which is a good sign of internal problems.

Inspect the transfer-case in the same manor. Observing the fluid that is drained can give you a basic idea towards the overall condition of the unit, but remember to pull the fill plug before you pull the drain plug, I get more into that later. Again due to the overall age of the truck I would expect chain stretch, something that will generate noise and if let go too long can allow for a popping sound as the chain slips, all the way to damaging the case itself. If the unit doesn’t seem to have the appropriate amount of fluid in it, I would take a close look at the output shaft seal at the yoke. If it has been leaking for a while there is most likely evidence of it underneath the cab floor. If there doesn’t seem to be a leak there you’re probably good to go, but if it seems to be leaking severely I would take a closer look to check the rear bushing. If the rear bushing has failed and let go for any amount of time, it can ruin the rear half of the case. If you pull the fill and fluid just runs out like it’s been overfilled, most likely the seals between the transmission and transfer-case are bad allowing transmission fluid to enter and overfill the transfer-case. It won’t particularly hurt the transfer-case, as they both use ATF fluid, but will need to be addressed should you find this condition exists.

Those are just some items to look for when inspecting the front half of the drive-train on these trucks. It may seem like a lot, but it’s really not. It’s just with an older, possibly higher mileage truck some items I would recommend looking at. Its way better to head things off before they get to the point of where they could cost you more down the road.

 

I have the Auto-trac T-case, I was under the impression that regular ATF will infact cause damage??

I'm about 99.7% sure this truck was a garage queen. The frame still has that black coating on at least 98% of the frame.and the under side looks very clean compared to some of the other truck i looked at that were many years newer.

Some excellant information BTW, much much MUCH appreciated. If you think of anything else I outta check that please do mention it!!

 

Your right in that the AutoTrac transfer-case does require it’s own fluid, it still won’t cause immediate failure, but the AutoTrac II fluid is designed for proper operation of the clutches in the AutoTrac electronic transfer-cases and continuous use of use of regular ATF can hurt the clutches in the unit. You may notice a grinding sound or feel and see clutch material in the oil when changing it after ATF has been in the unit for some time. Royal Purple also has a fluid that is reported to be a replacement for the AutoTrac II fluid.