I have 87 yj with little modification.  I picked it up for 350.00 and have a lot of work to do.  I would like use the jeep for plowing snow, pulling my 18 foot boat and hunting.   It currently has the 4.2 backed with the auto tranny.   I have torn the motor down and it is sound around all the cyl. and at the manifold.  The plans i have are to do a general re-man on the motor and reinstall with an RV cam, an offenhouser manifold, and a 4bbl carb.  I will also be removing the fan for an electric unit, and doing a electirical/ ignition system upgrade.  A 3 1/2" lift with an extra leaf,  and 33"  tires will be the rolling stock.  I will be adding a set of rear discs to the package as well as the external electric pumps for fuel and hydrolics I want to get rid of as many of the vacumes as possible therefore I cant see any way of keeping the auto.   The questions I have therefore, are multiple---Will an the stock AX15 bolt up,  without too much aggrivation?   I dont perticularly want to get into changing main shafts on a tranny.   Can the AX15 handle the type of duty that I want it for?  My boat weighs around 1000 lbs and has a tounge weight of 350lbs.   Are there other trannys that can handle this type of workout availble?    I don't have any need for a NV4500,  thats overkill plus the cost even at the junk yard is higher than I really want to spend.  HELP!  

      All I want to do, is may be save you some greef in your life. I think I understand the line you are thinking down. You are talking, recamming you 4.2 with a RV grind. Cams such as these don't have much of any over lap, so they make good vacume. Hang on, it only gets better. The trany in your YJ is the AMC 999. This trany is the Mopar 904 works in a AMC spec case. This is a very good trans, and stronger than most would think. The 904 (999), is nothing more than a down sized Mopar 727. The good news is it needs no vacume in put like the GM slush box (peanut butter drive), so no mods needed because of low vacume cams. With not much more than a cluch pack up grade, valve body kit to make it more friendly to manual shift in puts, and a good trans cooler, close to bullit proof. I know of guys hanging these units on 500 hp small blocks. You have to keep them cool, so the cooler (mine is a 15000 gvw) is I would say a must. A guage would be a plus for towing, and plowing. If you work them hard, they build a little more heat than the 727, and won't shed it as fast because of the smaller mass of the parts. But this lower mass all so frees up some horse power to the ground. If your worried about the trany being the week link, don't. Your lucky you did't end up with the factory manual from 87. The biggest weak spot may be the NP207 transfer case behind the trany. But thats like saying the Dana 30/35 axles are weak. I would say that will depend more on how you drive it ....... and what day of the week it was built on. Hope this was some help, and you can keep the skin on your knuckles. One more thing and I'll shut-up. The 4.2 head dosn't flow very well at high RMP. If you stick with the smaller 390 cfm 4 barrel, you can build a lot of low end torque. It will feel like more engine than it is when you make the big torque numbers under 2500 rpm. Thats where these mills really shine.  

I've always heard autos are better for plowing, but the AX15 should be good for what you want to do. one possible problem, not all auto equiped engines are drilled for clutch bearings.  

Hey, thanks for the advise on the auto tranny in my wrangler,  If it is possible to use it and expect it to work,  I wouldnt mind keeping it the long term is to renovate the entire thing (jeep), and use it as a second to my regular driver so it wont see daily action in traffic or anything.  You said that it a smaller version of the 727,  will it have the same fitting on the case for the cooling?  I have a dual cooler for a 727 out of a race car,  It came with a set up for a flex fan and remote application.  I of course would eventually like to have the V8 swap and a auto trans with it,  but w/ 3 sons and a wife, things dont always happin in my time frame. So I am trying to make do with the strongest parts avail. any other IDEAS you have would be greatly appreciated.    

             You should be able to use that cooler, but let me ask you frist if you live up north. If you do, this is what I have found. Keeping an auto trany cool is the best thing you can do for them, but. Don't ya hate that word? A trany should, and has to be able to come up to temp to work right. A stand alone cooler like you are talking about can keep your trany under that temp on a driver, more so in the winter time. The 904 & 727 will become sluggish, like they are running on grape jelly. So that cooler could be over-kill. I run the factory cooler, with a 15,000 GVW cooler after it. This helps the trany come up to temp faster in the winter. Keep in mind too, these tranys don't pump in park. In cold weather letting the Jeep warm up in neutral will all so help it to last longer. So you're not dropping a stone cold trany in gear. Hope this was some help.