Learn Me: Part-Time 4WD at the Challenge

The idea to run a modified 4WD truck in the Challenge has crossed my mind a few times since I've been following the event. They seem cheap enough, powerful enough, and plentiful enough to make a good platform for a build. Has anyone run anything with a proper 2/4Lo/4Hit 4WD system, especially with a manual transmission? If so, how has the experience been? Of particular concern to me is driveline bind on sticky tires (broken axles and T-Cases), and general breakage of the larger number of moving parts.

Please share all you know.

Having done a lot of DD'ing and aggressive street driving in a vehicle with that kind of drivetrain, you will get driveline bind in 4WD modes, you'll feel it and hear it and it will slow you down. Only way it might be helpful is if it gains you more on drag launches than it costs you in power lost to bind further down the strip.

I know when Jeeps at moab forget to unlock their t cases they go around corners on the street like: chirp chirp chirp chirp chirp. Sounds awful, and there is no high load or high speed. Just a left turn at a stop light. 

I don't know why I've only ever seen it at moab, but the one week I was there I saw it like 4 times.

I really want it to be good, but I don't think it will be.

If it a late 80s or early 90s GM you could theoretically just toss in an AWD astro transfer case. They can't handle too much power but at least in an s series truck it is mostly bolt in. Make some subie guys scratch their heads, wishing for a V8.

In reply to barefootskater :

This was my back-up plan. My understanding of the BW4472 transfer case is that they can take a bit of a licking, and would be an awesome compromise for traction/bind.

In reply to Robbie:

Could this be a result of them all having lockers/spools in both axles? Rather than just a 4WD issue?

Robbie said:

I don't know why I've only ever seen it at moab, but the one week I was there I saw it like 4 times.

Could be serious offroad rigs at a major offroading destination running Detroit lockers, they don't always unlock...

Edit: D'oh, beaten.

whiskey_business said:

In reply to barefootskater :

This was my back-up plan. My understanding of the BW4472 transfer case is that they can take a bit of a licking, and would be an awesome compromise for traction/bind.

In reply to Robbie:

Could this be a result of them all having lockers/spools in both axles? Rather than just a 4WD issue?

 

I've had several 4x4 trucks without spools or lockers and nothing good happens handling wise on asphalt when they're in 4 x 4.  If you had enough horse power that traction was an issue on wide corners it would probably be an advantage but I think that would be more than offset by the weird behavior on tighter corners.

Yep when I put my Sammy in 4WD on slick wet roads, it improves forward traction but handling gets real weird real fast.

In reply to APEowner :

That was what I worried about. Alternately, could 4WD be switched to 2Hi for autocross, and use 4Hi for drags? Would running in 2Hi have similar issues? 

2Hi is just like a regular RWD car, as long as you don't have any kind of front diff that could act on the axles without power like a Detroit locker or spool, ar a clutch-type with aggressive coast lockup.

Of you're not running lockers or spools or LSD at either end, 4wd is just 2wd. But worse actually than fwd or rwd with a spool, because both inside tires would spin when accelerating out of a corner.

I guess I just assumed if you were locking the center you would also lock side to side.

Plenty of full time 4wd transfer cases from the 70s still available for peanuts that will handle v8 power.

Do it!

oldopelguy said:

Plenty of full time 4wd transfer cases from the 70s still available for peanuts that will handle v8 power.

70’s-80’s K5 Blazer, remove top, NP203 transfer case, lowering springs and sticky tires being spun by one of my 6.0’s from my totaled Yukon Denali’s

Or buy my latest totaled Yukon Denali and chop it up, remove interior and everything else you don’t need and keep the stock drivetrain.

Why wouldn’t a seriously lightened GMT800 Denali work? AWD 335-345hp 6.0

In reply to ebonyandivory :

Didn't realize the blingy trucks got AWD instead of 4WD, if I can get one of those guys for Challenge money that would be mint. I'll shoot you a DM.

I think the AWD was a Denali thing. 

In reply to oldopelguy :

Can you elaborate on this? What kind of t-cases? And any behind a stick?

All three manufacturers used the NP203 behind manuals or automatics.  They are heavy but usually nearly free when you find them.  Otherwise, all the Jeep 219/228/229/242s can be adapted to manuals and automatics.

GameboyRMH said:

Robbie said:

I don't know why I've only ever seen it at moab, but the one week I was there I saw it like 4 times.

Could be serious offroad rigs at a major offroading destination running Detroit lockers, they don't always unlock...

Edit: D'oh, beaten.

Spools or lockers will chirp and skip tires going around corners, but it's *much worse* when you leave it in 4wd. It all comes down to the tires driving in different size circles, and something has to give. All wheel drive vehicles have a diff in the middle as well as on the ends, where a 4wd locks the front axle to the rear axle. 

If you are going to use a Ford 4wd, an important thing to remember is that the front gear ratio is usually a hundredth higher than the rear (my '96 F-150 has 3.55:1 rear/3.54:1 front).  This makes the front want to lead when the front axle is powered. It also means that, if you don't get it out of 4wd before you get it on a good surface, it'll bind up. A buddy of mine had a 4-cylinder early Ranger that bound itself to a stop. It didn't even have the power to back up. An old farmer came along, laughed at him, and picked up the back of the truck with the scoop on his tractor. With the stress relieved, he took it out of 4wd and drove off. 

whiskey_business said:

In reply to barefootskater :

This was my back-up plan. My understanding of the BW4472 transfer case is that they can take a bit of a licking, and would be an awesome compromise for traction/bind.

 

 

the 4472 transfer case is what is behind the trans in the syclone/typhoons. they are known to hold up to pretty decent power, north of 500. i have heard they dont like to be behind a manual trans though due to shock loads.

dean1484 said:

I think the AWD was a Denali thing. 

Denali and Escalade shared a drivetrain in the GMT800 era. 6.0, 4L65, AWD. Everything else got 5.3, 4L60, 4x4.

So what transfer case has a diff and mounts to a T-5?

Certainly wouldn't have anything to do with the concept of taking a rwd T-5 out of a Mustang and plopping in a Jeep T-5 and trying to make an awd Fox body. Nope I never thought about that before.

RossD said:

So what transfer case has a diff and mounts to a T-5?

One of the full-time Borg Warner QuadraTrac from a Jeep CJ should do the trick.  If you're lucky, you might even be able to find a Jeep that has one already bolted to a T5.  

In reply to RossD :

Wonder what the older Quadra-Trac might bolt up to.

RossD said:

Certainly wouldn't have anything to do with the concept of taking a rwd T-5 out of a Mustang and plopping in a Jeep T-5 and trying to make an awd Fox body. Nope I never thought about that before.

Back in the 80s, there were 55-57 T-bird kit cars that used a Bronco II frame. I wonder if the solution to this problem might be to drop a Mustang body on an AWD Explorer frame.