Pulling a trailer with 237 HP

[Mr Black]

I have been after a R model to restore and the best one I have found (in terms of condition) is a '81 with the 237 HP Mack engine. The truck will most likely be used for local container work (42 tonne GCM). I was after a later model with the 4 valve 300/350 hp but am now keen on this '81 with the 237hp. I don't know much about Mack engines but have been told to ignore the low hp figure on the 237hp because it has high torque.

My question is whether this thing is going to be able to pull a trailer for local work or will it be a slug in the modern world? It will be doing the same work as our truck with a mechanical Formula 300 Big Cam Cummins. Do you think the 237hp can do the job or am I crazy for trying? Can always be re-powered later but probably not smart to buy it if it is really only suited for rigid work. I won't get the chance to try it with a trailer before buying it.

Any input from anyone who has had experience with the 237hp engine or knows about them would be great.

Thanks

[GearheadGrrrl]

It'll work, but be seriously underpowered at 42 tons, with a 237 that's not even 6 HP/ton. On the flat, top speed will be at best about 100 KPH after a kilometer or two. Gradability may not be adequate either, unless it has the 6 speed "low hole" transmission- When the 237 was introduced maximum gross weight in most of the U.S. was only around 33 metric tons. I'd suggest holding out for at least 300 HP. Where are you going to work this truck?

[Freightrain]

It will get you there, but very slowly compared to anything late model.

I drag my stuff around with 180 hp. It gets there, but don't be in a hurry or find any big hills.

[bullhusk]

A good time tested motor! There are some Redi Mix Co's in my area still using them to haul 10 & 11 YDS ! there are some things that will help you along here like what trans, rear end ratio and so on, most came with a 4.17 or a 4.64 and I've seen some of the mixers with 6 speeds and a 5.13 (Ithink) with a top speed of 60 flat out! So your area is the most important, your terrain? flats, hills and so on?? Local flat not many hill ?? buy it! Good Luck

BULLHUSK

[Mr Black]

It'll work, but be seriously underpowered at 42 tons, with a 237 that's not even 6 HP/ton. On the flat, top speed will be at best about 100 KPH after a kilometer or two. Gradability may not be adequate either, unless it has the 6 speed "low hole" transmission- When the 237 was introduced maximum gross weight in most of the U.S. was only around 33 metric tons. I'd suggest holding out for at least 300 HP. Where are you going to work this truck?

Yeah, my gut reaction was that it is far too underpowered but I have had no experience with Macks so thought I would put the question out there. Some Mack fans have said that the Mack 237hp pulls like a 300+ hp Cummins but I find that hard to believe. The one I am looking at has a Mack 10 speed box - not sure about the diff ratio. It is just for capital city work but does have to hit the highway - will probably be too slow. Hard to come by nice R models in Australia. There are a few 4 valves around but nowhere near as tidy as this '81 237hp. Thanks for your response.

[Mr Black]

A good time tested motor! There are some Redi Mix Co's in my area still using them to haul 10 & 11 YDS ! there are some things that will help you along here like what trans, rear end ratio and so on, most came with a 4.17 or a 4.64 and I've seen some of the mixers with 6 speeds and a 5.13 (Ithink) with a top speed of 60 flat out! So your area is the most important, your terrain? flats, hills and so on?? Local flat not many hill ?? buy it! Good Luck

BULLHUSK

Thanks Bullhusk - I think it will be underpowered but I am still tempted. It's a very tidy truck for its age.

[Superdog]

If I had a dollar for every ton of freight hauled by & still being hauled by an "underpowered" 237 Maxidyne, I would be debt free,restore every truck I own and build the buildings to store them,purchase Mack from Volvo and still have enough left to bail our country out of the mess Obama has gotten us into. The 237 is probably the best engine ever made by anyone,period. The only thing underpowered is today's mindset that you have to have 400 + hp to move anything.

[39 Baby Mack]

Well put Mike!

Ron

[2stacksuperdog]

We had a '74 DM tri-axle with a 237 6 speed. More people would open the hood on it to see what it had for power and wouldn't believe it was only a 237. In 6th gear it would go from 35 to 75 mph. Don't sound underpowered to me.

[GearheadGrrrl]

If it has a 10 speed, it may not be a 237... 237s are high torque rise engines that usually came with a 5 or 6 speed wide ratio transmission.

[Mr Black]

If I had a dollar for every ton of freight hauled by & still being hauled by an "underpowered" 237 Maxidyne, I would be debt free,restore every truck I own and build the buildings to store them,purchase Mack from Volvo and still have enough left to bail our country out of the mess Obama has gotten us into. The 237 is probably the best engine ever made by anyone,period. The only thing underpowered is today's mindset that you have to have 400 + hp to move anything.

Great response!!!

I am tempted to just buy this thing and see how it goes. I tend to ignore hp ratings given that our 300 mechanical big cam feels like it has more power than some modern engines that are rated at almost twice the hp. Still, 237 seems low but I am not a hp ego maniac and would be very happy if it could earn the same wage as a truck with twice the power!!

[Mr Black]

If it has a 10 speed, it may not be a 237... 237s are high torque rise engines that usually came with a 5 or 6 speed wide ratio transmission.

I could be wrong as I am new to Mack but I don't think we had many 5 or 6 speeds in Australia - either that or I just haven't come across them. Mainly I have seen quads or 10 speeds in R600 models and 12 speeds in R700 models over here.

[other dog]

I'm with Mike, Ron, and 2 stack. It might be a little slow to get going, but once you do, then it's on! And like they said, the terrain is a big factor. If you're mainly on flat ground you'll probably love it.

I once took a 50,000+ lb. load from Va. to Washington, Pa. with a reload of steel coils in Butler, Pa. going back to Va.in a 237 powered F model. Yeah, it was slow- 2nd. gear on a lot of the hills, but it got the job done.

[steve p]

mr black a 237 will out pull a 350 small cam cummins all day every day ,don't forget our speed limit here is 100k not 70+ mph like the yanks have ,I had a 237 with a12speed new from the factory, the beauty of a 12 or a10 speed mack box you can drive them as a five speed or split unlike a bush ranger.don't forget that most of the road trains of 70's were r600's with 237 @ 120 t rating. so it's capable of doing the job

[kscarbel]

Overnite Transportation ran thousands of 237-powered F-785ST tandem tractors all over America. They performed superbly and delivered impressive fuel economy. Founded by the legendary Harwood Cochrane, Overnite's success was built on the back of the 237 engine. You'll be fine. I sold ex-Overnite F-785STs that were overloaded to 90,000-95,000 pounds..

[theakerstwo]

The 237 is good for 55 mph grossing 72000 but it is slow on hills and also don't let some one set the fuel up very much.

[vision386]

I agree 100% with Mike! I've run 237 Maxidyne/5 speed combo's properly geared that would will out-pull a 400 Cummins,BUT speed, top end,thats a different story..............but personally,i'd still give it to the Mack...........................Mark

[bullhusk]

mr black a 237 will out pull a 350 small cam cummins all day every day ,don't forget our speed limit here is 100k not 70+ mph like the yanks have ,I had a 237 with a12speed new from the factory, the beauty of a 12 or a10 speed mack box you can drive them as a five speed or split unlike a bush ranger.don't forget that most of the road trains of 70's were r600's with 237 @ 120 t rating. so it's capable of doing the job

Well mr black there's you answer! No one can beat a man thats been there an done it! Like I said DM 600 & 800 Mack mixers haulin 10 & 11 yds (between 72,000 & 80,000 on three axles) and there still pullin the same loads that the newer 350 to 450 hp trucks are doin! and they will be doin it when the newer ones are in the junck yard!

Buy it and good luck

BULLHUSK PS if you look at the F mod. Certified mixer, that was a 15 to 18 yd mixer and all that was???? A 237 with a 6 speed Maxi trans and those mothers were over 100,000lb's loaded!!

[Mr Black]

Thanks to all for your responses - this has been very helpful. I think I will just take the risk and buy it. If it doesn't work out I could always repower it or sell it.

[RFCDrum]

Thanks to all for your responses - this has been very helpful. I think I will just take the risk and buy it. If it doesn't work out I could always repower it or sell it.

There were a lot of two stick 6 speeds in OZ at one time and also in New Zealand. I think Fletchers or one of those fleets ran a lot of R models with 6 speeds. I have seen R models in Oz that had the ten so I don't think it was a transplant. Crank up the fuel and blow some coal with her.

Rob

[Maddog13407]

slow? ill take everygood running 237 no one wants, I have a few tired 673's and 711's id like to replace. might not be a speed demon but drive a 170hp 673 and tell me how slow it is...

[RFCDrum]

Just dug out my copy of The Bulldog Breed by Bruce Honeywill Wentenhalls ran R models with 6 speed lo holes in their fleet.

Rob

[Dougsr]

I hauled logs with an old Mack with the 237 with a 5 speed. 60 mph was it. I was not in the hills so it was not to bad to drive. You could not shift out of 5th gear until 45 mph on a hill.

Doug

[Freightrain]

might not be a speed demon but drive a 170hp 673 and tell me how slow it is...

My point. I'm not that heavy, but any kind of grade and I'm slowing to a crawl and lots of gear changing.

[GearheadGrrrl]

I drove a 237 at around 32 tons )metric) back in the 70s when we had an 88 KPH speed limit in the midwest. It was quite on top of the job, pulling our short small hills in top gear and dropping a gear for the longer grades coming out of the river valleys. Also drove a 237 one day at around 40 tons and it was clearly beyond it's comfortable limits- Even thought the route was flat as a pancake freeway, it barely made it to that 88 KPH speed limit after a kilometer or too and was running wide open most all the time. On a very minor 1% or so grade it was down to around 70 KPH, barely able to maintain the freeway minimum speed.

So while the 237 puts out an honest 237 and then some HP and will run with the 300s from Cummins and Detroit, on the used truck market here in the U.S. a 285 or 300 can be bought for about the same price and is a better choice if you're going to be running around the 36 ton (80k pounds) legal limit. That said, at 30 tons or less the 237 works fine, but if you buy that 237 and work it at 42 tons I suspect you'll soon be back here asking how to "turn it up" to 300.