The 237 Mack Tell Me About It. . .

[B61TENDT711]

Factory power settings:

Hp n TQ numbers ?

Maximum Rpm ?( redline)

Max sustained rpm ? ( highest rpm safely maintainable)

Can the motor be turned up ?

if so what kind of numbers can be turned from it ?

year range ? cubic inches ?

I want to some day own a military 5ton 6x6 truck tractor powered by the Mighty 237 Mack, so i am trying to learn any and everything i can about the motor if you have any info about the engine or even the Mil-spec 5ton truck it came in do tell i have open eye's n ears. . .

Mike

[cgallamore]

it has been many years since i drove a 237 but i do remember i liked the lowend tork. never worried about max rpm,s because they do their best pulling at 900 to 1100 rpm,s if you can find the parts to put an aftercooler on it you will love it , feels like double the horse power it only brings it up to a 285 but it feels like a lot more. hope this helped.

[cgallamore]

the aftercooler attaches to the right side of the engine,the bigest problem is the air filter and plumbing,gotta cut some on the hood to get the other pipe thru,if you can find an old cocrete mixer truck a lot of those had 285,its just a 237 with an after cooler

[cgallamore]

if you notice 70,s and erly 80,s some air cleaners have two pipes going thru side of hood thats the after cooler (ie)285 the ones with only one pipe thru the hood are 237.nothing goes out in frount of the radiator,

[cgallamore]

if you go to a web site called GSA or google goverment surplus autions you will find lots of military tractors cheap

[B61TENDT711]

yea that i know there all Cummins powered unit's or they have the Multifuel unit. . .I don't want either of those 2 i want the mack powered unit. . .

Mike

[HK Trucking]

it has been many years since i drove a 237 but i do remember i liked the lowend tork. never worried about max rpm,s because they do their best pulling at 900 to 1100 rpm,s if you can find the parts to put an aftercooler on it you will love it , feels like double the horse power it only brings it up to a 285 but it feels like a lot more. hope this helped.

Actually, the operating range of the 237 (ENDT675) is 1200 - 2100 RPM. Lugging it at 900 - 1100 RPM as you suggest would lead to it's early demise.

Torque rating of the 237 is 906 ft. lbs.

Putting an intercooler on it will not help much unless you also uprate the fuel system to ENDT676 specs (285 HP, 1080 ft. lbs.)

.

[B61TENDT711]

Whoa 900TQ !

Now that thing is a beast i'm told these things can be rapt right out to 2,400rpm shifting threw the gears and it'll hold 2200rpm sustained.

any truth to this ?

Mike

[Lmackattack]

Whoa 900TQ !

Now that thing is a beast i'm told these things can be rapt right out to 2,400rpm shifting threw the gears and it'll hold 2200rpm sustained.

any truth to this ?

Mike

max RPM with no engine load was 2300

Max RPM with load was 2100

you can spin them to 2300 But I think most will agree its better to keep it at a max of 2100.

[B61TENDT711]

Now you call the 237hp an ENDT675 as where the 237hp Military truck had a ENDT673 Confusing . . .

I want to try n Find a Mack powered M52A1 5ton 6x6 truck tractor 237hp Mack turbo diesel 5spd spicer 6453? i think anywho 6.44 gears 11.00-20 tires.

I was hopping to find one these trucks some day swap on a set of 11R24.5's add some stack's and roll on. . .

Mike

[HK Trucking]

Now you call the 237hp an ENDT675 as where the 237hp Military truck had a ENDT673 Confusing . . .

I want to try n Find a Mack powered M52A1 5ton 6x6 truck tractor 237hp Mack turbo diesel 5spd spicer 6453? i think anywho 6.44 gears 11.00-20 tires.

I was hopping to find one these trucks some day swap on a set of 11R24.5's add some stack's and roll on. . .

Mike

The ENDT 675 is a Maxidyne engine, used with a 5 or 6 speed transmission. The ENDT 673 is a Thermodyne engine, Depending on whether it's an A, B, or C, it could be 205 HP, 225 HP, or 250 HP. The ENDT 673 operating range is 1500 - 2100 RPM, they were usually backed by a Duplex, Triplex or Quadruplex transmission to provide close enough gear ratios to allow the engine to stay in it's operating range.

[B61TENDT711]

ok so then the Military truck is really the ENDT675 as it has a 5spd manual transmission. . .that is how they got a 237hp Mack turbo diesel ?

either way the transmission is a 5spd there was no other trans option 5 forward speeds 5th was OD in the multifuel n mack engine 5th DD was for the Gas engined truck.

Mike

[ThaddeusW]

Now you call the 237hp an ENDT675 as where the 237hp Military truck had a ENDT673 Confusing . . .

I want to try n Find a Mack powered M52A1 5ton 6x6 truck tractor 237hp Mack turbo diesel 5spd spicer 6453? i think anywho 6.44 gears 11.00-20 tires.

I was hopping to find one these trucks some day swap on a set of 11R24.5's add some stack's and roll on. . .

Mike

The 673 is short for the END673 or EDNT673 (T is for turbo model) model of engine which came out in the 50's and powered B, G, and L models as well as early R, F and DM models (I probably left out a few). It is also known as the Thermodyne Diesel engine. The number 673 stands for the displacement in cubic inches.

Now the 237 was the successor to the 673 and looks very similar to the 673. The number 237 is not the displacement but rather the horse power output of the engine. Its model number is gives as ENDT675, just 3 more cubes then the previous 673. It was given the name Maxidyne. Maxi is short for maximum and dyne is a unit of force who's name is derived from the Greek word dynamis, which means power. So Maxidyne means Maximum power . It was a wide torque band engine so instead of needing 9/10/13/18 speed transmissions to keep the engine in its peak operating band you just needed 5 or 6 gears which greatly simplified shifting. It was introduced around 1963 1966/67 and quickly became popular for its grunt and pairing with simple 5/6 speed gear boxes.

Now the M39's (The M52 is the tractor version of the M39) Were powered by the Mack ENDT673 Thermodyne, not the ENDT675 Maxidyne. The reason is Because the M39 was introduced around the early 50's, the same time the 673 Thermodyne came out. Here is a link to the Olive-Drab info page. As you can see the 673's were rated at 210HP @ 2100RPM and 610 ft-lbs.

Your best resources for military vehicle Information is Olive-Drab or the Steel Solders forum.

[HK Trucking]

The 673 is short for the END673 or EDNT673 (T is for turbo model) model of engine which came out in the 50's and powered B, G, and L models as well as early R, F and DM models (I probably left out a few). It is also known as the Thermodyne Diesel engine. The number 673 stands for the displacement in cubic inches.

Now the 237 was the successor to the 673 and looks very similar to the 673. The number 237 is not the displacement but rather the horse power output of the engine. Its model number is gives as ENDT675, just 3 more cubes then the previous 673. It was given the name Maxidyne. Maxi is short for maximum and dyne is a unit of force who's name is derived from the Greek word dynamis, which means power. So Maxidyne means Maximum power . It was a wide torque band engine so instead of needing 9/10/13/18 speed transmissions to keep the engine in its peak operating band you just needed 5 or 6 gears which greatly simplified shifting. It was introduced around 1963 and quickly became popular for its grunt and pairing with simple 5/6 speed gear boxes.

Hi Thad.

Actually, the END 673, ENDT 673, ENDT 675 & 676 were all 672 Cu. In. displacement, same as the old Lanova engine they were derived from. The Maxidyne was introduced in 1967 IIRC.

.

[Rob]

Hi Thad.

Actually, the END 673, ENDT 673, ENDT 675 & 676 were all 672 Cu. In. displacement, same as the old Lanova engine they were derived from. The Maxidyne was introduced in 1967 IIRC.

.

There were a few put out to trucking companies in 1965 for testing in B model chassis. The engine series was introduced for public sale in mid 1966 in the R model series of truck.

This was per my grandpa whom had two B models with very early ENDT-675 series engines backed with five speed transmissions.

Rob

[ThaddeusW]

Hi Thad.

Actually, the END 673, ENDT 673, ENDT 675 & 676 were all 672 Cu. In. displacement, same as the old Lanova engine they were derived from. The Maxidyne was introduced in 1967 IIRC.

.

Thanks for the correction Herb. Somehow I confused the R model intro date with the Maxidyne intro date.

Here is a question then, was the 711 indeed 711 cubic inches?

[Rob]

Thanks for the correction Herb. Somehow I confused the R model intro date with the Maxidyne intro date.

Here is a question then, was the 711 indeed 711 cubic inches?

707 but referred to as 711. I don't know why unless just for discernment from it's gas counterpart.

Rob

[HK Trucking]

707 but referred to as 711. I don't know why unless just for discernment from it's gas counterpart.

Rob

I think it was because it was 707 CID, and 211 HP.

[other dog]

I think it was called a 711 because after the chief engineers had perfected this particular engine they said "hey,let's all go down to the 7-eleven and get a slurpee to celebrate!". While they were standing in the 7-eleven store parking lot enjoying their slurpees one of them said "what are we gonna call this new engine?". They all looked up at the 7-eleven sign...the rest, as they say, is history.

That's just my theory.

[other dog]

707 but referred to as 711. I don't know why unless it was because 707 was already taken by some airplane and they didn't want any confusion.

Rob

that's right.

[Rob]

that's right.

Stupid airplanes. Always getting in the way of something.

Rob

[B61TENDT711]

So then if the 673 was designed for the multi speed trans then how come it help up to pulling 75-100K-Lb loads with just a 5spd trans mission ? wouldn't the truck have lugged = blown head gaskets ?

I was always told NEVER lug a Thermodyne !?!?!?

http://www.memphisequipment.com/Products/5ton.asp

Engine #1

Cummins...Model NHC-250

Horsepower...250 @ 2100 RPM

Displacement...855 cu. inches

In-Line 6 Cyl. Non-Turbocharged

Engine #2

Model...Mack ENDT-673

Type...In-Line 6 Cyl. Turbo Charged

Horsepower...220@ 2100 RPM

Displacement...672 cu. in.

Engine #3

Hercules/Continental

Model LDS-465-1A

Horsepower...205@ 2600 RPM

In-Line 6 Cyl. Turbo Charged

Displacement...478 cu. in.

Engine #4

Continental...Model R6602

Type...Valve in Head, 4 cyl, 6cyl

Horsepower...196 @ 2800 RPM

Displacement...602 cu. in.

Bore...4 7/8

Stroke...5 3/8

Oil Capacity...22 qts

Clutch

Spicer...15" Single Disk

Electrical System

24 Volt (optional 12 volt)

Transmission

Type...5- Speed, Manual

Spicer...6353, 5th Gear overdrive

Spicer...6352, 5th Gear Direct Transfer Case

Rockwell...Model T-138

As you can see there is nothing but 5 speed manual transmission options !?!?!?!?

Mike

Edited October 25, 2009 by B61TENDT711

[B61TENDT711]

I bet the 5spd works with the Mack as the Cummins is also a 1500-2100rpm ranged engine, and because of the lower revs the Mack n Cummins units got the OD 5spd manual trans. . .

this dealer posted has the 673 available in 220hp,another dealer where i saw the mack engines was clark truck parts. I emailed them and asked about the 237hp Mack diesel and yup your right it was the ENDT675 they got a deal on a few dozen of them and where swapping out the 673 for the 675. . .

If i was to get my hands on the Mack powered M52A1 tractor would i be better off swapping the Thermodyne 673 for the Maxidyne 675 as they did because the truck is only a 5spd ? would it then be more worth while to swap in the 350hp motor with the 7spd trans if i'm going threw a the trouble of transplanting ?

Mike

Edited October 25, 2009 by B61TENDT711

[ThaddeusW]

So then if the 673 was designed for the multi speed trans then how come it help up to pulling 75-100K-Lb loads with just a 5spd trans mission ? wouldn't the truck have lugged = blown head gaskets ?

I was always told NEVER lug a Thermodyne !?!?!?

My guess is the very tall rear ends (tall meaning higher ratio number) makes up for the lack of gears. These trucks weren't speed demons but rather built for serious hauling over rough terrain. The ratio is given as 6.44:1 which is pretty darn tall.

If i was to get my hands on the Mack powered M52A1 tractor would i be better off swapping the Thermodyne 673 for the Maxidyne 675 as they did because the truck is only a 5spd ? would it then be more worth while to swap in the 350hp motor with the 7spd trans if i'm going threw a the trouble of transplanting ?

As for swapping motors, the transfer case might be a weak point if you put in a high torque motor. But I am sure swapping in a 237 Maxidyne would be fine as long as you don't abuse it. The only thing to worry about when doing engine swaps in those M39's is the amount of length you have before you cant properly couple the transmission to the transfer case. Meaning you cant have a transmission that's too long. I have seen CAT 3208 boat anchors put in them but not something as big as an E6-350. The 237 Maxidyne with a Mack 5 speed might be a great fit.

[B61TENDT711]

Good stuff thanks for the info

Tho i was also planning on swapping out the 11.00-20's for 11R24.5's which will bolt right up and clear perfectly, which would then get away from a split rim tube type tire no stock's but can special order to a tire that most truck shops have in stock plus it gains me 5-7mph in max road speed which helps on a 50mph. . .

Now will the 237 be able to pull the 2.5 inch taller tires with 6.44;1 gears and 5 forward speeds ?

Mike

Edited October 26, 2009 by B61TENDT711