4 Spd. Auto Questions

[carguy87]

So I lost second gear in the Eagle Sunday, and am at that point where I am seriously thinking about that long pondered change to an auto with O/D.  I have a 4.2L, bored .030, 4.0 head and cam, and F/I.  I am thinking about using a 42RE or something along that line.  I was wondering which trans would best hold up to my application and still leave some lining in my wallet.  And I do use this as a tow rig, so strength is important.  Any opinions?

[carnuck]

AW4 is what you want ('91 up and the tcase or a 1" spacer ring to run the Eagle tcase). 42RE needs to be flushed down the toilet.

AW4 is 3.5" longer so you add the 1" ring and it's 4.5" longer. You have to cut the floor behind the driver's seat for the extra length. Aside from that, you need the computer and a speedometer adapter plus custom trans crossbar.

[priya]

AW4 is what you want ('91 up and the tcase or a 1" spacer ring to run the Eagle tcase). 42RE needs to be flushed down the toilet.

AW4 is 3.5" longer so you add the 1" ring and it's 4.5" longer. You have to cut the floor behind the driver's seat for the extra length. Aside from that, you need the computer and a speedometer adapter plus custom trans crossbar.

I know this is probably a dumb question and I think I already know the answer but with the AW4 being 4.5" longer does that mean you have to shorten the rear driveshaft and lengthen the front driveshaft?

Also, is the AW4 from a Jeep?

[carguy87]

I don't know what I was thinking, maybe I was just too tired last night.  I want the AW4, even have a rebuilt never installed one sitting on my shelf at home.  Maybe I was thinking 42RE because that is what computer and harness I installed for the F/I setup.  Yes, AW4 is from a Jeep, yes, both shafts have to be modified, and I am still debating the T/C.  If I snag one from an XJ, I would have my VSS and just have to rig my speedo, or just go off my tach like I currently do, since my speedo only works over 50mph.  Why do you have to cut the floor?  I see plenty of room to put my Ford tool to use and not have to cut floor and pull up carpet.  The shift linkage will have to be changed, but I can grab that with the wiring harness and computer from the donor XJ.  The X-member was an obvious thing, and aside from that, all that is left is modifying the rock guard for the T/C to allow for the new extended length front driveshaft.  Would be nice to have that O/D, wonder what kind of MPG's I could pull down.  Now I just have to decide which O/D ratio I want, I have seen them with two different ones. 

[carnuck]

On the VSS, are you going HO or Renix EFI? HO '91 to '95 is easiest (all under the hood except trans controller) '91 YJ Wrangler has a "pass thru" cable (screw on) and VSS combined (only year). Your speedo probably doesn't work till you get up to speed because the gear in the transfercase is missing tooth/teeth (friction grabs it and starts it functioning), the cable is broken and again friction grabs it or something in the head or cruise control junction is worn out.

   The floor cutting may not need as much or could possibly just need Ford wrench adjustment to clear the speedo assembly (if you go XJ tcase) We converted a 2wd Spirit to an SX4 and needed some (but not all) the cutting Max98059 did. He's busy with a 4.0L swap now because he killed the 4.2L (blew the headgasket after overheating bad last summer)

   We used the column shifter on the Spirit (worked easily) by moving the shift lever on the AW4 (1 nut and it has 4 positions for adjustment) Your MPG will be improved more by the EFI than O/D, depending what your gear ratio is. (I wouldn't use O/D if you have tall tires and/or taller than 3.08 ratio)

[captspillane]

The VSS from an XJ works in an Eagle transfer case just fine. Likewise the AMC speedometer cable will work in an XJ transfercase.

I prefer the older two piece VSS along with a VSS from a Dodge Dakota. You then need a speedo cable from a J10 truck or CJ Jeep along with a plastic adaptor from 5/8" to 7/8" threads. I prefer this because it lets me unscrew the speedo cable without dumping fluid everywhere.

For my AW4 installation I will be using the original AMC driveshafts. I install XJ NP242 transfer cases using the short Eagle front transfer case yoke and I retain the long front yoke for longer transmissions like the AX15 and AW4, which solves the front driveshaft length change.

On the rear I've used the XJ slip yoke installed on the Eagle driveshaft with a 3" pipe installed inside the sliding part of the original AMC driveshaft. The pipe keeps it from sliding together. If you let it continue to operate the driveshaft will fall out on its own. With the longer AW4 I won't need the pipe, since it will be bottomed out at all times, negating the risk of the driveshaft falling out.

The AW4 has been installed without cutting the floorpan. It will hit but tilting it slightly fixes that. Mine is already tilted by simply installing two washers between the body and crossmember.

[captspillane]

The AW4 is a better transmission than the 42RE in stock form. That's very true but don't dismiss the 42RE entirely. I like mine so far and I've also seen a Jeep guy advertising that he'll take your 42RE and combine it with parts from a 47RE to make essentially a 47RE with AMC bellhousing casting. That makes it the best transmission to find for extreme power builds.

[BenM]

I always thought the problem with the 42RE was having a computer to control it.