Replacing gears in tranny?

[AstroWyo]

I want to keep my AWD transfer case (BW4472). I'm completely convinced (am I wrong?) that it's better in snow than it would be to put in 2 sp transfer case. I have a 4Runner, too, and have compared the two.

Still, I want that low crawler gear. I know I'll need to change out the gearing in my axles and it's on the long list. When I was working on VW's we (I never did it) used to be able to change out gears in the tranny to affect ratios. Has anyone looked at changing out the gearing in the 4L60? I'm not sure it would make sense with the 4 speed but I rented a Chevy Traverse the other day and I think it has an auto 6 speed. (Pretty nice machine, BTW, though not as roomy as our vans.) Is there an auto 5 or 6 speed where one could trade out one of the low gears? Maybe better to go with a manual 5 speed?

Maybe the level of computer control is too high these days to do this cheaply enough. Maybe the auto 5 speeds are too incompatible electronically with an old astro. I don't want to have to get too far away from what I already have in my '96. I see a rat's nest of wires on the horizon if I change too much.

I know that this low gear issue has been dealt with before but, so far as I can tell, the approach has been to go with a 2 speed 4wd trans case. I don't trust that option for giving me the best performance in snow.

Any thoughts on attacking it from the transmission rather than the trans case with just a low crawler gear?

[ihatemybike]

To my knowledge there are no regearing kits available for the 700R4/4L60E. The 3.06 1st gear is already pretty low. Grumpy's 330k mile transmission has pulled the van through many off road situations that amazed many when I had it wheeling at the Badlands Off Road Park and didn't let me down doing a little exploring in Moab, UT.

This is a video of Grumpy in 1st gear pulling itself up a rocky ledge. The van had no power problems, just a slight lack of breakover clearance till I picked a slightly different line.
http://www.youtube.com/watch?v=tmuYpUcXFfQ

Has your wheeling had you longing for the lower gears? Has the van let you down by being unable to go places?

Since you have the BW4472 of the 1998 and older vans, if you want to keep the AWD it's possible to add an underdrive unit such as the Klune-V Extreme Underdrive. These will bolt up between the transmission and the transfer case and usually have 2.72:1 or 4:1 reduction gears in them. Downside to these is they are not cheap (couple grand), and would require custom front and rear drive shafts and modification to the trans/tc supporting cross member.



Related
On the 1999 and later AWDs, it's my theory that they could have an electronically controlled 2-speed transfer case swapped in and then wired in such a way that the computer could activate the 4HI solenoid when slip is detected, the exact same way the AWD is controlled stock. I think with a 5 position switch the van could have 2WD, AWD, TC Nuetral, 4HI, 4LO available.

[LiftedAWDAstro]

The transfer case in the TrailBlazers is a NV236. It is bolted to a 4L60E and has AWD, 2HI, 4HI N, and 4LO. I would imagine all you would need is the TCCM and selector switch.

[ihatemybike]

Is the NV236 AWD computer controlled like the NV136?

[AstroWyo]

There's a thread ("Nobody has done an NP236 swap yet, right? Will it fit?") There were some TCCM issues, I guess. He didn't do it.

I did some more surfing. Best I can come up with is the Selec trac NP242 with a Novak conversion kit for the 4L60. I didn't check price. Don't even know if it'd all work. I'm not sure it's been done as I haven't found anyone who's done it to their van. The NP242s I've found for sale were pretty cheap, though.

I didn't know about the underdrive for AWD. I've only seen them for 2wd, especially hot rods. That's a very cool idea to explore.

I take my 4Runner up a very steep and long road with a steep and high drop off. I have to do much of it in lo on the ascent and descent and figure the Astro would need the same. Maybe I need to change out the gearing in the axles first and test it. I'd hate to have to ride my brakes all the way down but I think I'd be fine on the climb up. Maybe I should just drive my 4 Runner up there but that makes too much sense. The van is more roomy.

Thanks for the ideas!

[RocKrawler]

bringing this thread back from the dead... I read that there is a GM version of the NP242 from the Hummer H2:

The Novak Guide to the
New Process / New Venture Gear 242 Transfer Case

The Jeep NP242 transfer case was introduced in the 1987 model year as a replacement for the NP228. The 242 premiered in the XJ Cherokee / Wagoneer and MJ Commache as the SelecTrac option. It was used in the 1991-1998 ZJ Grand Cherokee. The 242 persisted throughout the full run of XJ Cherokees and continued on in the 2002 KJ Liberty.
The 242 was originally tagged as the 242AMC, and as ownership of AMC was taken over by Chrysler, it was later designated as the 242J. This transfer case was later called the NVG (New Venture Gear) 242. Despite the different nomenclature, very few mechanical changes were required or made throughout their production span.
Earlier attempts at torque-biasing transfer cases were spotty in their success, beginning with the QuadraTrac in the 1970's and continuing with the NP219 and NP228. The 242 has continued in the trend of chain-driven cases and has technically and commercially been more successful than its predecessors.
Features
The 242 has a driver's side front output and centerline rear output. The NP242 features two ranges; a low range gear that is a respectable 2.72-to-1 low and a direct-drive in high range. It features three drive modes; 2wd, full-time 4wd and part-time 4wd, yielding:

* two-wheel-drive, high (direct-drive)
* four-wheel-drive, high (48/52 differential torque-biased-drive)
* four-wheel-drive, high (locked, part-time)
* neutral
* four-wheel-drive, low (locked, reduction-drive)

This tag indicates a 231J transfer case, with a part number of 52098886, a build date of 5-7-96 and a gear ratio of 2.72:1. Though Full-Time is the nomenclature used, this is a position that is used sparingly, as component wear throughout the geartrain and tires is a result, in addition to decreased fuel-efficiency.
Early 242s from 1988 through 1991 featured a conventional mechanical (cable) drive speedometer output. In 1992, Jeep introduced a three-wire, digital square wave Vehicle Speed Sensor (VSS), in the vein of modern automotive systems.
The design of the 242 is fairly good. They were engineered for durability and simplicity of build - both an advantage to the OEM assemblers as well as individuals servicing them. The NP242 transfer case has turned out to be stronger than expected. Most of our customers choose to retain their Jeep 242 with their conversions. It is very common for them to offer good service behind some of the strongest engines and transmissions.
The 242 weighs about 85 lbs.
Identification
This transfer case is identified by its red and silver tag on the rear of the case. They are also easily identified by appearance. They feature a six-bolt front face and a longitudinally ribbed barrel case.
There is a GM version of the 242 as used in the H1 Hummer (1990- ) and the later H2. It features a different front face bolt pattern that is incompatible with the Jeep six-bolt styles. This GM version is rated at a stronger duty by virtue of its stronger output shaft. It may feature a 1" wide or a 1.25" wide chain.
Interestingly, New Venture documents show the 242 as being rated at 1486 ft. lbs. of torque. This is probably determined based on Full-Time position usage. Experience would say that this is a very conservative number for all other positions.

My questions:
Are the output shafts on the same side of the H2 and the Astro?
Are they electronically controlled or can they be bolted in to the earlier (mine is a 96) vans without the TCCM we lack?
Wouldnt this be ideal, incorporating the AWD for snow/ice and locked 4wd for off road, PLUS 4LO with 2.7 gearing for rougher stuff?

[LiftedAWDAstro]

The problem with using the 242 case from the H1 and H2 is they were bolted to the 3/4 ton transmissions...the 4L80E. I have to imagine the input shaft sizes are much bigger than what is used in the 4L60E. The 4L60E's use a 27 spline input and I think the 4L80's use a 32 spline. Other than that it would work as the Astro and H2 are both driver side drop. The H2's were all electric shift I think so you would also need the TCCM and wiring.

[doyoulikeithere]

Sounds like maybe the shopping list just grew to add a Hummer V8 and Transmission to go with that transfer case !!
Lol, Can he do it? Hummers use a SBC dont they?

[Cobra]

yup the H2's use the LQ4 6.0 liter V8 that i want

[brokenwrench]

I want to keep my AWD transfer case (BW4472). I'm completely convinced (am I wrong?) that it's better in snow than it would be to put in 2 sp transfer case. I have a 4Runner, too, and have compared the two.

Still, I want that low crawler gear. I know I'll need to change out the gearing in my axles and it's on the long list. When I was working on VW's we (I never did it) used to be able to change out gears in the tranny to affect ratios. Has anyone looked at changing out the gearing in the 4L60? I'm not sure it would make sense with the 4 speed but I rented a Chevy Traverse the other day and I think it has an auto 6 speed. (Pretty nice machine, BTW, though not as roomy as our vans.) Is there an auto 5 or 6 speed where one could trade out one of the low gears? Maybe better to go with a manual 5 speed?

Maybe the level of computer control is too high these days to do this cheaply enough. Maybe the auto 5 speeds are too incompatible electronically with an old astro. I don't want to have to get too far away from what I already have in my '96. I see a rat's nest of wires on the horizon if I change too much.

I know that this low gear issue has been dealt with before but, so far as I can tell, the approach has been to go with a 2 speed 4wd trans case. I don't trust that option for giving me the best performance in snow.

Any thoughts on attacking it from the transmission rather than the trans case with just a low crawler gear?

there are numerous cases that will bolt to the 4l60e and there are cases that can be sequentially stacked for ultra low gears.