4.0 engine swap

[Ronner]

No, you need not fix anything of mine. Take a 4.0 and its' transmission and stick it in your truck. The 4 or 5 transmissions that you will replace each year will tell you that "if you are going to go to the trouble of replacing the motor & trans then going with something bigger would be better."

[Mikel]

This is my uneducated opinion:

- The AX15 or AW4 transmissions that most 4.0s came with are very nicely sized for the power and torque of the 4.0. Yes, a M715 is a heavier vehicle, but with the crazy gearing, it shouldn't be as much of a problem. The 15% OD in the AX15 would give you an extra 10-15MPH cruising speed - Very nice, IMO, but I'm not sure how the NP200 would like the extra RPMs.

I would be VERY interested in seeing how a 4.0/AX15 would do in an M715

[2ndA]

Then put one in. The NP200 will have to go, too, though. Meanwhile, I'll try and buy up some trannys so I can retail them to you at a couple hundred bucks a pop profit.

[moosejr]

The power to PULL it is not usually the concern in towing something, .it is the ability to STOP it! I understand the concept of "doing what you have to" with pulling the truck behind your TJ, however, think of the costs of consequences. You get into a situation where you can't stop that thing, ..and somebody could end up severely injured, or worse. Can you afford the liability? While law enforcement in some states might not take a second look, I can tell you that in California, the Highway Patrol would likely escort you to the nearest scale,. .weigh it, check your GVW, write you a HEFTY ticket, and make you park the works until you can tow it legally and safely. The other concern that I always have with towing is "the tail wagging the dog". If the trailer is significantly larger than the tow vehicle, it could easily take over the combination, resulting in a fishtail that is unrecoverable. I worked for many years as a paramedic,. .saw WAY too many accidents caused by this.

[Roy]

My customers have been killing AX15s in XJ, YJ and TJ models as well as Toyota trucks with nothing more than larger tires for years. In the correct applications(READ: stock 1/4-ton or commuter) they can be fairly dependable. I would never recommend using one in a 5-6000 pound vehicle.
If the manufacturers thought they would have worked in those applications they woulda used em in J-trucks and the like.

[TheDude]

I might be swapping in a 258 or stroked 4.0 into my 715 if my previous power plant options aren't going to work out. The issue with the aw4 is heat, it creates a ton of it. With a large transmission cooler I have seen it hold up to some serious abuse. The AX15 on the other hand was initially designed for 1/2 ton drive trains like the aw4, but it's gearing is not adapt for a 5,000+ LB vehicle where the aw4 could take the excess weight displacement with the proper modifications. Also the AX15 is easily confused with the AX5 as the two share many similarities. Tall axle gearing would help but unless swapping in newer one tons the 5:89's may not be enough. Toss in a NV4500 for its lower overall ratios, mate it to a twin-sticked lomax 4:1 equipped dana 300 and keep it jeep!

(just a very broad thought)

RM

[hardtail70]

It is not against the law to be stupid. However if you do something stupid and hurt or kill someone that has consequences. On that note that is why I sold my f250 and bought an f350 for towing purposes. My trailers all have brakes and when I am towing an unfamiliar load I hit the cat scale before hitting the open road. Here is a prime example of why we need better enforcement of non commercial towing of trailers.

[phoenix]

If you have a rear seat in a small jeep, you can register it as a car. therefore there is no limit to hauling like in a truck. Some may think that in a short wheelbase vehicle that the trailer would want to make it swing out. I think it is closer to a semi truck than you think. It is the same principal. I use quite a bit of weight on the hitch and it squats down a few inches. Maybe my TJ is magic or something. I have never had it act squirly on me or anything. Yes you have to expect it to brake slower. No I would not want to drive it in stop and go traffic. Aside from the short wheelbase, my TJ has 1/2 ton running gear with Dana 44 axles front and rear. I have 1/4 inch thick 2"X5" front and rear bumpers, a massive tire carrier in the back, and a 1/4 and 1/2 inch thick grill guard. The suspension is a teraflex long arm system that uses 2 inch diameter solid (not tubing) suspension arms. I have probably added 500 lbs to the Jeep in metal. This should make my TJ around 4400 lbs. that is not too far from a standard 1/2 ton 4X4 truck. The TJ has a much better front/rear weight ratio than a truck though so I dont have to worry about too little weight in the rear end. I have an AX15 trans in my TJ and have had no problems with it at all. I had the clutch fork retainer clip break which made me take the whole drivetrain apart to fix the clutch fork that fell inside the bellhousing. I had purchased a new clutch just because I was in there anyway, but the original clutch disc seemed to have little wear on it and looked as thick as the new clutch disc. The Jeep had 97,000 on it at that time.

If you use the arguement that the brake system is not capable enough, you have not been around long enough or have not worked on older trucks with no power brakes and drums on the wheels. No matter what kind of big drum brakes you have on your 5/4 ton truck both front and rear, my TJ with power disc brakes will have better braking. So unless you want to park your M715 because it is unsafe... Isn't that pintle thingy on the back of my M715 for towing? with non-power drum brakes? are you nuts? It can barely stop itself! Oh, thats right, the military said it was OK.

[Mikel]

If you have a rear seat in a small jeep, you can register it as a car. therefore there is no limit to hauling like in a truck. Some may think that in a short wheelbase vehicle that the trailer would want to make it swing out. I think it is closer to a semi truck than you think. It is the same principal. I use quite a bit of weight on the hitch and it squats down a few inches. Maybe my TJ is magic or something. I have never had it act squirly on me or anything. Yes you have to expect it to brake slower. No I would not want to drive it in stop and go traffic. Aside from the short wheelbase, my TJ has 1/2 ton running gear with Dana 44 axles front and rear. I have 1/4 inch thick 2"X5" front and rear bumpers, a massive tire carrier in the back, and a 1/4 and 1/2 inch thick grill guard. The suspension is a teraflex long arm system that uses 2 inch diameter solid (not tubing) suspension arms. I have probably added 500 lbs to the Jeep in metal. This should make my TJ around 4400 lbs. that is not too far from a standard 1/2 ton 4X4 truck. The TJ has a much better front/rear weight ratio than a truck though so I dont have to worry about too little weight in the rear end. I have an AX15 trans in my TJ and have had no problems with it at all. I had the clutch fork retainer clip break which made me take the whole drivetrain apart to fix the clutch fork that fell inside the bellhousing. I had purchased a new clutch just because I was in there anyway, but the original clutch disc seemed to have little wear on it and looked as thick as the new clutch disc. The Jeep had 97,000 on it at that time.

If you use the arguement that the brake system is not capable enough, you have not been around long enough or have not worked on older trucks with no power brakes and drums on the wheels. No matter what kind of big drum brakes you have on your 5/4 ton truck both front and rear, my TJ with power disc brakes will have better braking. So unless you want to park your M715 because it is unsafe... Isn't that pintle thingy on the back of my M715 for towing? with non-power drum brakes? are you nuts? It can barely stop itself! Oh, thats right, the military said it was OK.

You may have the illusion of better brakes because a TJ weighs 2/3 the weight of a M715. Even if the brakes are better, you still don't have the weight or wheelbase of a M715 for towing. Towing such heavy loads with a TJ is pure madness.

[randyscycle]

I used to have a '94 Grand Cherokee, 4.0L, towing package, full time 4WD and it had the exact same axles and brakes as the XJ. Just that small increase in weight and size on those brakes rendered them almost inadequate. The XJ's I'd owned previously stopped well, but I never towed with them. The Grand by itself was woefully underbraked.

I then purchased a 6X12 enclosed motorcycle hauler (single-axle no brakes) That combination with two motorcycles at approximately 900 lbs or so, plus the weight of the trailer, made the Grand weak to say the least, trying to climb anything more than a slight grade, and stopping without planning was not very safe either. In fact, in a panic, trying to stop it was dangerous. Trailer brakes may have helped, but probably not much.

I bought a 1 ton Dodge full size van to pull the same trailer, and it was like night and day. With that van, 6 motorcycles (3 in the van and 3 in the trailer), two people and all their gear, I can accelerate, and stop very easily and safely.