mj payload & towing capability?

[zzze]

My question is this on the standard shortbed 4.0 L 5 speed non-metric ton mj, what is the towing capacity, and payload?

[Harper]

No publication I could find shows payload for the truck itself. There should be a Fed Cert label on the driver's door beneath the latch. It shows the gross vehicle weight and gross axle weights. According to my Owners' Manual, the towing capacity for the shortbed 4.0, 2x4 is 2000/300t.w. with a class I hitch and any tranny, and 5000/750t.w. with a class III hitch and the AW4 w/cooler. It also notes that trailer sway control and equalizing hitch required for weight over 3500#.

[Eagle]

IIRC, the payload for the standard (non Metric Ton) MJ is 1478 pounds.

[jimoshel]

Remembers correctly.

[kyleag89]

And when towing any more than 600lbs the trans mount likes to break! (original 1989)

[ParadiseMJ]

And when towing any more than 600lbs the trans mount likes to break! (original 1989)

 

...of course, depending on the trans, and the gearing, and the wheels, and the hitch, towing capability will be different.

 

i.e. if you have an AW4 with a D44 with 4.10 (or even 3.55) gears and 235's it's going to be a whole different story if you have a BA-10 with a D35 and 3.07's with 31" tires.

 

1400 lbs. of dirt (or whatever) plunked in the bed is also going to going to be different than trying to TOW a 3500 lb. boat with 500 lb. tongue weight...and a small5th wheel set-up, still different. You just gotta remember that the little MJ is surely a tough truck but it'll never tow like a 1/2 ton full size with a V-8. Just not enough beef.

 

I tow a little 5X6 utility trailer behind my XJ with about 500 lbs. (about 1K lbs. total) of gear over hill and dale and hardly know it's there except for the stiff suspension on the trailer. I also tow a 18' light weight (about 400 lbs. total weight) canoe trailer with superb suspension and unless I look in my mirrors it's like I'm free wheeling.

 

 

Then, there's the brakes. If you're towing something that weighs more than the truck, you got issues unless you have good trailer brakes.

[AMC-MJ]

All MJ's in bed payload is 1,475-LB's, except for the metric ton which is 2,209-LB's in bed.

 

Max towed load goes as follows:

2.5L 2,000LB's 2.8L 4,200LB's 4.0L 5,000 LB's.

 

brakes aren't so much the limiting factor as the lack of weight of the truck itself the brakes have plenty of power to bring 235/75R15's to a dead stop but if the payload exceeds that of the truck's weight it'll push it even with a 4 tire dragging :thumbsup: so the weight of and MJ + 4 dragging tires = 7,500LB's of Forward force so 5K is the rated limit for safety :thumbsup:

 

 

Mike

[1tonMJ]

What would be needed to convert a regular MJ into the 1 ton? Just bigger springs I would imagine.

[Pete M]

springs (front and rear), shocks, and a beefier rear axle (which includes bigger brakes). :thumbsup: I'd also include a trans cooler is auto, and if I were building an MJ to haul that much, I'd go with even deeper gears than the factory gave 'em.

[AMC-MJ]

Yup I can relate to the upgrading of the MJ to tow some stuff !

 

Current setup:

AMC-150 I4, AX-4, D35 with 3.73s dose quite well but . . .

 

Future setup:

AMC-290 V8, AMC-T5, AMC-20 with 4.11s Will n do much better !

 

Why the little 290 V8 instead of the 242 I6 ?

 

4.0L = 195hp & 235tq !

 

4.9L = 205hp & 260tq !

 

It'll prolly still get about 15-17mpg even the 4 banger only dose 16mpg !

 

 

Mike

[Incommando]

The factory rating of the 290 is old enough to be a gross rating, which is probably 20% higher than the net ratings that became standard around 1973.

 

Example:

 

A 1972 Jeep 304 had 210 hp/290 TQ

a 1973 Jeep 304 had 150HP/245 TQ

 

A 1972 Jeep 360 had 245 hp/365 TQ

a 1973 Jeep 360 had 175HP/285 TQ

 

Contrary to "common knowledge," emissions was not the big factor: the change from "gross" to "net" ratings was.

 

Under the modern system, that 290's factory rating would probably be around the 150 HP that its larger replacement, the 304, had. That 4.0L is closer to a late model 360 than anything. When combined with the off-roadabilty and ease of starting, etc... that comes with EFI, I can see which engine I would go with.

 

I would avoid the AMC M20. Get a FSJ or MJ AMC M23 rear. One-piece axles from the factory and better tubes. Or find a MJ D44. I have owned M23's and D44's and I would not swap either for the other, they are that close. Nor would I swap a

9'' or 8.8. But a M20 needs some $$$ to equal them even if the center section is shared with the M23.

 

If MPG is what you need, find a TJ NSG370 6spd to swap. My KJ with a 3.7 has one, and with 3.55 gears and heavy e-rated 245/75/16 MT/R's I get 18 mpg (21 hwy) in spite of weighing nearly 1,000#'s ( 4,033 lb vs 3,057 lb) more than a stock XJ and having more HP & equal Tq when compared to a 4.0. Probably a much easier swap than a V8 conversion, too.

[AMC-MJ]

Those are the net power numbers the 290s gross eating was much higher !

 

The 01-06 4.0L made 195 net horse power and 235 net torque.

 

The 66-69 290 made 205 net horse power and 260 net torque.

 

The 290 was rated for 225 gross horse power and 300 gross torque, a fellow AMCer ran a stock 290 and it spun 205/260 net numbers the 290 is stronger then the 304 as it has a slightly more aggressive camshaft and a 10.2:1 compression ratio.

 

Don't forget AMC under rated there engines ;) !

 

Hot rod mag did an arcticle on the old engines one of them was the 4bbl AMC-390 which was rated for 315 gross horse power well when they dynord it the AMC-390 actually turned 332 net horse power, then HOUR being HOUR they tweaked it some and with a simply carb rejet and spark recurving they got 347 N-hp.

They said AMC did this to keep off the high risk insurance lists.

 

Mike

[Incommando]

The factory ratings were widely reported as being gross until 1973, as the charts indicate. Even if some few 290's got the 4bbl and the 10:1, most were 2bbl & 9:1. I guess a 4bbl 10:1 may have been around 165-170 net? Don't forget the better heads that came along for the 304 and the larger displacement.

 

Yes, playing with HP numbers, especially among the big engines' numbers, was very common for that era due to insurance reasons. It is no mistake that the classic engines, like the 426 Hemi or 427 side-oiler were ALL rated at about 425 HP, the insurance industry's max. at one time. All of the companies did. You could achieve better than factory numbers with "blue-printing" and by fine tuning them. Many magazines, including hot rod, did this for many makes and found the same things occured to all of them, not that enthusiasts needed a magazine to tell them that. Even Mopars very pedestrian 383 4v's 335 HP was rated higher than the 390's magazine result but it, too, was under reported at that 335. The insurance industry did not just effect AMC.

 

We will have to agree to disagree as I have my sources that differ from yours, obviously, and it is way off of the topic already and going further away. Please, just no one cite WIKI like it is a legitimate reference source... :D

[AMC-MJ]

The 304 was larger but lower compression with a more tame camshaft also :thumbsup: The 290 4bbl with 10.0:1 which was actually 10.2:1 not that ot matters was the base engine for the AMX's and Javelins so it had to be some performance minded, which is why it got the higher compression ratio and a more aggressive camshaft then the 304 jeep engine.

 

the 304 360 and 401 Jeep engines had 8.3-8.5 ish compression ? as where most of the AMX & Javelin 290 343 360 390 401's had 10/10.2:1 and a select few had 12.2/12.5:1 making for a not so fair comparison.

 

i am sure the 10:1 AMX 360 made more power then the 8.3:1 Jeep 360 and i bet the 8.35:1 401 made less power then the 10:1 401, The higher compression dose make a difference and steeping the camshaft up 1 or 2 notches also makes a difference even if the both idle smooth at 750rpm . . .

 

I just used the AMC-390 as we were talking AMCs . . .

 

I just simply stated the 390 was rated for 315G-hp but actually turned 332N-hp according to HR Mag.

I am well aware every manufacturer did the same thing.

 

As for the 290 one of the 2 AMC forums should have the thread pertaining to the 205/260 numbers, either way ill be going with a 290 V8 in my MJ few mileage is not of any concern to me i wanted peppy yet drive able truck and i simply was not going to do and engine swap to have a 6cylinder regardless of cost or complexity :thumbsup:

 

Ok your right, back on topic,

MJ payload & towed load ratings.

2.5L = 1475 & 2000 2.8L = 1475 & 4200 4.0L = 1475 & 5000 only exception was the Metric ton which was rated for 2209 payload.

 

Now as for the MJ dually I don't know its rating . . . I don't think many where made don't seem to be much known about them from what i can find . . .

 

Mike

[jpnjim]

AMC switched from gross HP/torque to net for the 1972 model year.

 

(1971 was the final year for gross numbers from AMC).

 

 

These numbers have been widely available, and common knowledge since AMC published them almost 40 years ago.

I have no idea how they could be in dispute now.

Side effect of the 'information age' I guess. :dunno:

 

AMC engines:

 

Gross 1968-69 ratings

 

290 2bbl 200hp@4600 285tq@2800 9.0:1cr code M

290 4bbl 225hp@4700 300tq@3200 10.0:1cr code N

343 2bbl 235hp@4400 345tq@2600 9.0:1cr code S

343 4bbl 280hp@4800 365tq@3000 10.2:1cr code T (W code used on leftover 67 Rambler/Marlin 343's)

390 4bbl 315hp@4600 425tq@3200 10.2:1cr code X (W code on Canadian 390 2bbl)

390 S/S AMX rated 340hp 12.3:1cr code Y

 

Gross 1970 ratings

 

304 2bbl 210hp@4400 305tq@2800 9.0:1cr code H (M code on export 304 4bbl)

360 2bbl 245hp@4400 365tq@2400 9.0:1cr code N

360 4bbl 290hp@4800 395tq@3200 10.0:1cr code P

390 4bbl 325hp@5000 420tq@3200 10.0:1cr code X

390 4bbl 340hp@5100 430tq@3600 10.0:1cr code Y (Rebel Machine & AMX/3 only)

 

Gross 1971 ratings

 

304 2bbl 210hp@4400 300tq@2600 8.4:1cr code H (M code on export 304 4bbl)

360 2bbl 245hp@4400 365tq@2400 8.5:1cr code N

360 4bbl 285hp@4800 390tq@3200 8.5:1cr code P

401 4bbl 330hp@5000 430tq@3400 9.5:1cr code Z (early 71 10.2:1cr)

 

Net 1972-73 ratings

 

304 2bbl 150hp@4200 245tq@2500 8.4:1cr code H

360 2bbl 175hp@4000 285tq@2400 8.5:1cr code N

360 4bbl single exhaust 195hp@4400 295tq@2900 8.5:1cr code P

360 4bbl duel exhaust 220hp@4400 315tq@3100 8.5:1cr code P

401 4bbl 255hp@4600 345tq@3300 8.5:1cr

 

 

360 4bbls were available with single, or duel exhaust in many platforms,

once they went to net numbers (1972) AMC actually started rated the engines differently depending on the exhaust system installed.

 

All 304's were single exhaust, and all 401's got duels (in 72), so they only had a single rating for each of those.

[AMC-MJ]

There wasn't a debate as to what they were rated for, we were discussing what they actually made for power :thumbsup:

 

 

Mike

[Incommando]

So, to continue this ad ifinitum.... :D

 

If all we have is ratings, then the 304, which is rated higher than the 10:1 4v 290 in gross HP, may have made more than that engine in real life.

The rated HP is still valid as, if everyone was doing it, it is safe to assume that the competition was, as well, so.... the factory published ratings are really the most reliable numbers to go with, or at least the most consistant.

 

If the rating of the '71 304 was higher than the 290 & dropped 60 hp to 150 on the net rating in '72, then I think it is safe to assume that the 290 would have had an equal drop, not withstanding the hot rod article or whatever the true numbers may or may not have been.

 

Wasn't it hot rod the got a "stock" megaton Poncho Catalina 2+2 to do like a 4.3 sec 0-60 and, in fact, that stock 421 was anything but and the frame had even been hole-sawed for weight savings. Magazines are in business to sell magazines after all.

 

I only included a great upgrade to increase MPG because of this: "It'll prolly still get about 15-17mpg even the 4 banger only dose 16mpg !"

 

Now if anyone wants an Edelbrock AMC V8 Performer intake and Edlebrock/Carter 600 CFM AFB with electric choke (they came off a running engine) for $150 each or $250 together, give me a ring... :cheers:

[jpnjim]

Looks like that thread got deleted.

 

 

I guess I should've gone to bed at 10:30 last night,

instead of digging out every AMC engine code & hp/torque rating, from 1968 to 1973,

and then manually typing them here.

 

 

edit....

 

 

:cheers: :cheers: to the mods. :D

 

Should've known you wouldn't leave me hanging. :doh:

 

 

AMC switched from gross HP/torque to net for the 1972 model year.

 

(1971 was the final year for gross numbers from AMC).

 

 

These numbers have been widely available, and common knowledge since AMC published them almost 40 years ago.

I have no idea how they could be in dispute now.

Side effect of the 'information age' I guess. :dunno:

 

AMC engines:

 

Gross 1968-69 ratings

 

290 2bbl 200hp@4600 285tq@2800 9.0:1cr code M

290 4bbl 225hp@4700 300tq@3200 10.0:1cr code N

343 2bbl 235hp@4400 345tq@2600 9.0:1cr code S

343 4bbl 280hp@4800 365tq@3000 10.2:1cr code T (W code used on leftover 67 Rambler/Marlin 343's)

390 4bbl 315hp@4600 425tq@3200 10.2:1cr code X (W code on Canadian 390 2bbl)

390 S/S AMX rated 340hp 12.3:1cr code Y

 

Gross 1970 ratings

 

304 2bbl 210hp@4400 305tq@2800 9.0:1cr code H (M code on export 304 4bbl)

360 2bbl 245hp@4400 365tq@2400 9.0:1cr code N

360 4bbl 290hp@4800 395tq@3200 10.0:1cr code P

390 4bbl 325hp@5000 420tq@3200 10.0:1cr code X

390 4bbl 340hp@5100 430tq@3600 10.0:1cr code Y (Rebel Machine & AMX/3 only)

 

Gross 1971 ratings

 

304 2bbl 210hp@4400 300tq@2600 8.4:1cr code H (M code on export 304 4bbl)

360 2bbl 245hp@4400 365tq@2400 8.5:1cr code N

360 4bbl 285hp@4800 390tq@3200 8.5:1cr code P

401 4bbl 330hp@5000 430tq@3400 9.5:1cr code Z (early 71 10.2:1cr)

 

Net 1972-73 ratings

 

304 2bbl 150hp@4200 245tq@2500 8.4:1cr code H

360 2bbl 175hp@4000 285tq@2400 8.5:1cr code N

360 4bbl single exhaust 195hp@4400 295tq@2900 8.5:1cr code P

360 4bbl duel exhaust 220hp@4400 315tq@3100 8.5:1cr code P

401 4bbl 255hp@4600 345tq@3300 8.5:1cr

 

 

360 4bbls were available with single, or duel exhaust in many platforms,

once they went to net numbers (1972) AMC actually started rated the engines differently depending on the exhaust system installed.

 

All 304's were single exhaust, and all 401's got duels (in 72), so they only had a single rating for each of those.

[AMC-MJ]

It was there this winter . . . Well I guess when I get that far ill dyno the MJs 290 and are what she spins ?

 

I guess intill then its all he said she said !

 

 

 

Mike

[WahooSteeler]

reviving this thread.......ok, so with factory tow pkg, it is agreed that an MJ can tow up to 5000 lbs, proper weight distributing hitch yada yada yada. One thing I have not seen is if this is limited to the 2wd longbed, some other configuration, or is the same rating as long as you have the factory tow pkg. Almost ALWAYS when you see a "max tow rating", it is in one particular configuration. Anyhoo, what I'd really like to know, is there any info out there to say what an MJ could tow under 5th wheel configuration? Is there some formula a slide-rule geek can use to figure it out? Logic tells me in a small truck like this, it's still gonna be the 5k lbs, limited more by the strength of the trans, frame, etc. At least you'd gain the more stable setup and better weight distribution of a 5th wheel setup. On full size trucks, especially 3/4 and 1 tons, they are often rated for up to 10-20% more capacity under 5th wheel towing. I'm already assuming 5th wheel was never a configuration the MJ was rated for, but it'd be cool to know. Just one of those little tidbits of info that will bug the crap out of me forever if I don't see it in print somewhere. :dunno:

[johnj92131]

The 5000 lbs tow rating required Big Ton/Metric Ton package. The Dana 44 had brake shoes wider than the stock Comanche by 3/4 (?) inch. Also required the Big Ton/Metric Ton package and was only a long bed option. My 91 owners manual indicates both 2x4 and 4x4 could have the Big Ton package, but not available on the short bed.

[WahooSteeler]

The 5000 lbs tow rating required Big Ton/Metric Ton package. The Dana 44 had brake shoes wider than the stock Comanche by 3/4 (?) inch. Also required the Big Ton/Metric Ton package and was only a long bed option. My 91 owners manual indicates both 2x4 and 4x4 could have the Big Ton package, but not available on the short bed.

 

Even though anything I've ever read did not say you HAD to have Big Ton AND Tow Pkg, I assumed that was the case for a mid size truck to haul 5k lbs. So probably Tow Pkg got you to 3k lbs, then add Big Ton to get to 5k lbs capability. Still want to know if 5th wheel would increase that at all. Not that I'd want to have much more than 5k lbs pushing behind me, but again, just nagging at me to know. :wall:

[Pete M]

according to my 88 dealership brochure, the big ton package is not required for 5k towing.

 

What's required for 5k lbs:

-class 3 hitch

-prep package with heavy duty rear axle

-auto trans

-heavy duty cooling system

-p205 or larger tires

-full size spare

-heavy duty battery

-power steering

and any trailer over 1k should have a separate brake system on it.

 

Otherwise it's a 2k/class 1 towing capacity.

[WahooSteeler]

that's good info, cuz I have the factory Tow pkg. w/class 3 hitch.

[kastein]

Huh. I came pretty close to the bed max a few weeks ago...

 

I had a 4.0 (with manifolds and most accessories, approx 500lbs), an AW4+231 (120lbs or so), spare front/rear driveshafts (call it 40lbs), engine hoist (140lbs), toolbag (70lbs), 50lbs of spare fluids, 50lbs of cooking gear and food, 50lbs of clothes and camping gear, 50lbs of water, 50lbs of beer+cooler+ice, and some other stuff I'm forgetting... plus my 200lb fat @$$. I guess my estimate of 1400lbs was pretty close.

 

It rode like an elephant... a swimming elephant in heavy seas.