M931A2 engine/trans power restrictions

[RPMRPM]

I’ll start by saying I’m very well versed on the P7100 pump I daily a 98 ram with a 700 horse twin turbo 12V that I built the engine and transmission for and every 100-150k miles I tear the motor down and replace internals I see are worn, and replaced the clutches and steels in the automatic trans at the same time

But I just bought a M931A2 and I’m wondering what the weaknesses are of a 8.3/power restrictions, boost restrictions, etc catastrophic failures is the main thing in worried about id be fine doing a tear down every like 200-300k or even more miles if possible not required though, also ok the transmission front i have no experience with Allison’s the transmission in my 12V is a 47RE with 68 internals and custom increased clutch and steel packs so what kind of power with the Allison in a A2 handles and if it need to be rebuilt what will I be in a rebuild for parts to handle the power I can get outta the 8.3 under the previous requirement.

 

[NDT]

Search for posts by Simp5782 on the subject. He is the only one on here that put big power through the Allison and I can tell you it didn't go well. Hmm, 300K in a 931, your spine will need to be rebuilt before the 8.3.

 

[Csm Davis]

You can build the motor to big horsepower, transmission not so much. Get 7 speed or some other OTR truck transmission.

 

[WillWagner]

The engines in the 900 series are the thin deck style. Cummins had an issue with cracking blocks between the liners on the early 8.3s. Too much HP will kill it. Hell, trash trucks and busses killed them with only 200 hp with the duty cycle! And the MW/RSV is not as responsive to HP increases as the P pump.

 

[Karl kostman]

I know this is hind sight but I would say you would have done better to find The A1 trucks with the reliable as heck 855, they have always been my go to engine or just about everything I own and they are pretty tough unlike the little turbo job in the A2 trucks. I suppose you must have CTIS on your Truck? Be aware that can be another bugger to keep working and expensive but they do make a CTIS delete kit out there also, You will start thinking about that when you come out to leave in the morning and all 6 tires are flat and your in a hurry!

 

[RPMRPM]

I know this is hind sight but I would say you would have done better to find The A1 trucks with the reliable as heck 855, they have always been my go to engine or just about everything I own and they are pretty tough unlike the little turbo job in the A2 trucks. I suppose you must have CTIS on your Truck? Be aware that can be another bugger to keep working and expensive but they do make a CTIS delete kit out there also, You will start thinking about that when you come out to leave in the morning and all 6 tires are flat and your in a hurry!

Will the tires really go flat overnight, I thought they would only go flat after letting them sit over a long period of time? Also in the way of transmission durability if you would recommend going with an 855 big cam would I be better off just buying an M920 instead since they already had the 855 big cam with engine brakes, and they had the 16 speed air shift caterpillar transmission behind them that I hear is much more durable than the 939 series trucks, and better at handling power

 

[Csm Davis]

Check out,
Simp's M920 build thread

 

[NDT]

The Cat 7155 comes with it’s own set of issues, it can handle huge power but is full of finicky o rings that fail and then you are broke down. Most people end up swapping in a Eaton/Fuller. I haven’t yet. Mine still works perfectly.

 

[RPMRPM]

The Cat 7155 comes with it’s own set of issues, it can handle huge power but is full of finicky o rings that fail and then you are broke down. Most people end up swapping in a Eaton/Fuller. I haven’t yet. Mine still works perfectly.

What do most people go to an 18 speed manual? Like in a Kenworth, Peterbuilt, etc?

 

[Jbulach]

It would help if we knew how you will be using your truck.

 

[RPMRPM]

It would help if we knew how you will be using your truck.

It will be converted to a camper not towing anything heavy high end of weight will probably be 30k curb weight

 

[NDT]

For that duty you are fine with the 8.3/Allison with modest power increases. The 920 with it’s walking beam suspension will not be a good choice for a camper.

 

[simp5782]

What do most people go to an 18 speed manual? Like in a Kenworth, Peterbuilt, etc?

13 spd RTOO-14613 so you have a higher speed with the double Over. You do not need an 18spd in a 920 with 6.17 gears unless you are doing 150k weight all the time