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So who has bumped the power on a 6CTA cummins

Ford Mechanic

Active member
1,805
6
38
Location
Edenton, NC
I'd be more worried about the over driven transfercase
Why??? I thought the transfer case just couldn't handle the reduction of reverse in low? It's not like it's shifting in the t-case under acceleration. What was worrying me was the upshifts, it was really lunging every time it shifted. It hadn't done that before I turned the pump up.

I turned it down a half a turn, I'll see how it runs to marrow. I might just turn up the preboost screws some, what do I need to expect to adjust it? I under stand it's a star wheel in there. Is there something I need to loosen a set screw or somthing?
 
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Vintage iron

Active member
1,123
16
38
Location
Falmouth Ma.
The Allison transmission in the M939 series trucks can handle the increase in the power. My customer Steve put a 450hp Cummins 400 in his M929 dump truck with 1600's on it. He has been working it for a year now. He did his homework and found that the Allison transmission in our trucks are rated to 425hp.
 

Suprman

Well-known member
Supporting Vendor
6,860
693
113
Location
Stratford/Connecticut
I have them listed in the classifieds with dimensions. They were intended to mount above a radiator thats a bit lower than the one on a 5ton. Several commercial diesel trucks use this style. Look at the pics and let me know. will@pawnking.com
Will
 

4XDesign

Active member
Steel Soldiers Supporter
441
47
28
Location
Blythewood, SOUTH CAROLINA
I have them listed in the classifieds with dimensions. They were intended to mount above a radiator thats a bit lower than the one on a 5ton. Several commercial diesel trucks use this style. Look at the pics and let me know. will@pawnking.com
Will
Okay found them they are definitely big. I will have to pull some more measurements and ill let you know thanks again.
 

hklvette

New member
373
7
0
Location
Christiansburg, VA
The Allison transmission in the M939 series trucks can handle the increase in the power. My customer Steve put a 450hp Cummins 400 in his M929 dump truck with 1600's on it. He has been working it for a year now. He did his homework and found that the Allison transmission in our trucks are rated to 425hp.
Huh? I've seen conflicting reports on what the MT654CR can handle, but the highest I've seen is 300HP/950ft.-lbs. posted here on SS. Do you happen to have a source for the 425hp number?
 

Strouty

Member
55
10
8
Location
Maine
For those of you who have installed new GSK's, have you considered using a better harmonic balancer? Only reason is that I remember seeing notes in the parts catalog that the OEM balancer was for 2100 RPM or lower.

This is a great question, I know when I was looking at increasing the HP on my 3126 (civilian) that one of the requirements was to change the harmonic balancer. I am thinking there must be info available from cummins about this. These engines were in motor homes and those are usually the highest HP ratings.


Huh? I've seen conflicting reports on what the MT654CR can handle, but the highest I've seen is 300HP/950ft.-lbs. posted here on SS. Do you happen to have a source for the 425hp number?

I would love to see the spec sheet that says that, it would be nice to know. My guess is that someone was misinformed. I am going to swap in an MD3060P into my M931A2 and that is not rated anywhere near 425HP.
 

Tornadogt

Member
720
6
18
Location
Adkins, Texas
Marine engines (as in Boats) have the highest Hp and Torque ratings. They have a unique advantage of an endless supply of cool water for both the innercooler/aftercooler and engine coolant systems.
 

Moto2four

Member
108
0
16
Location
Baton Rouge,LA
I installed an egt gauge on my truck yesterday and had to turn the fuel rate way down. The previous owner had cranked up the fuel, and I was seeing 1400 on moderate acceleration.
 

nevrenufhp

New member
200
16
0
Location
Sacramento
I installed an egt gauge on my truck yesterday and had to turn the fuel rate way down. The previous owner had cranked up the fuel, and I was seeing 1400 on moderate acceleration.
Is there an air flow restriction? Even with the nut backed off, it shouldnt get to even 1300.
 
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