Power in M51A2

[akexc]

I'm looking for feedback from someone who has used this variation of truck with super-singles and is hauling heavy loads.

I'll start by saying I've been searching this forum looking at re-powering this truck, but (1). Can't find a great thread on the details of doing this, and (2). Not sure that it's needed.

I have been using this truck for personal use to haul gravel. I'm starting to discover all kinds of issues with this.

For starters, it just has no power. Or what power it has, is not very useable. Even empty, it is difficult to drive. You have to shift perfectly and stay in the sweet spot for RPM/torque, or you are constantly down shifting. That's a problem in itself. Extremely hard to downshift, to the point where in many cases, I have to stop and go back to first. I'm looking at the tranny to see what I might need to do here.

I realize that by having super singles on this, the final drive ratio has been changed so that it has effectively lost torque to the wheels. However, is it reasonable to expect that this makes it un-driveable? I can haul 10 tons of gravel, but it is a real effort to drive. Don't know top speed, because the speedo doesn't work yet, but I would guess no more than 35? Maybe less.

The transfer case won't stay in low, but you wouldn't use that on the highway anyway, right? (Another project I'm working on)

I'm looking at doing some work on both the transmission and transfer case, but even if they were in perfect condition, that's not going to help my power problem.

I reallize that the engine may not be up to snuff, but it seems to run reasonably well. Not sure how to test how well it's doing.

Should this truck with super-singles be reasonable to do what I'm talking about, or do I need to turn up the power on the engine to make it so? Or, do I need to re-power?

How do I determine if I'm not getting the power I think I should be.

Thanks.

 

[derby]

I have a 67' M51a2 with 1100"s and I was thinking about the singles for it also. This fall I hauled 35K Shell corn to the mill, two wagons in tow. There are a couple small inclines and a freeway over pass between here and there. Low range high gear no problems. I would not want to create any problems with the bigger tires. I think the truck has the power if it is running right. What size tires are you running?

 

[AMGeneral]

First,Just a few questions about your truck,I see it is an A2 model which should be a LDS 465-1A multifuel,if so,are you absolutely certain it has the non overdrive trans in it?(is 5th gear all the way to the right and foward twards the dash or backwards twards the seat?)

Second,How does it start? fire right up or do you have to turn it over for a while?

Lastly,Excessive smoke or little to none while pulling hard?

 

[akexc]

AMGeneral

Yes is does have the multifuel. Should have mentioned that. I am not certain about the overdrive, I have been unable to get to the tag to verify. Just basing that on what the technical manuals say should be there. However, without going out to look, I'm pretty sure 5th is all the way to the right and back towards the seat. Reverse is forward and to the left.

As far as firing up, depends upon the temperature. Warm weather, it seems reasonable. Not like my Powerstrokes, but starts after some cranking. Cold weather is a whole different deal. Additionally, it smokes all the time. From idle on up. Black smoke.

Derby, as far as your question on the tires, not sure. I was told they are super singles, and I know they are a larger diameter than stock, but without looking, I don't know what size. I will check for you

 

[AZDeuce]

akexc:

It sounds like your motor "may" be a little weak/wore out, it "should" start within 2-3 revolutions at the most in warm weather, YMMV in cold weather, and the black smoke should clear up once warmed up. (there will be a little)

5th gear should be all the way to the right and UP (if I remember correctly), this would indicate a overdrive transmission, and the correct one for a M51A2. If it shifts 5-th gear DOWN, I belive that indicates you have the transmission out of a gas engined 5-ton, WITHOUT overdrive, and all the wrong gear ratios for your multi-fuel engine.

If this is in fact the case swapping out to the correct overdrive transmission will probably solve most of your power/speed issues. I used to own a M52A2, and I'm pretty sure it shifted up and to the right for 5-th gear.

 

[jimbo*]

Well, since my M51A2 never leaves the ranch, I can't really answer as to road speed. It does, however, have plenty of power for my use at 25 MPH and under. It sits on 395/85R20's (46").

From your pic, it appears your truck sits on 16.00R20's (53")--definately power killers.

 

[BKubu]

Does it have the direct drive or overdrive transmission? If it has the latter, take out the overdrive transmission and install a direct drive transmission. You will lose some top speed (max speed will be about 46 MPH). On one hand, it sucks being able to ONLY drive at 46 MPH (now thinking about it, it might have been 47 MPH, but whatever). On the other hand, at least you will get to your top speed! I owned an M543A2 that weighed about what your truck weighed with the 10,000 pound load and that truck had plenty of power. The other killer...the tires as you have identified. These trucks are notoriously underpowered for road usage and you just killed it with those oversized tires. Take them off and put the 1100s back on. If you need aggressive tread and more traction, go with Michelin XLs, Firestones (can't remember the model #) or even Goodyear G177s.

 

[ken]

If the engine is smoking all the time. There is a good chance the waste gate for the turbo is stuck in the open position. This lets the exaust gas bypass the turbine and go strait out the exaust. Causing a low boost condition. You also might check the injectors. Or at least run some cleaner through them. If they arn't spraying correctly you will end up with alot smoke and low power. I don't have a M51. But i do have a M52A2 with the same drive train. And pulling my loaded M127 it can get to 55MPH with no problems. It takes a while but it isn't unreasonable. If your still unhappy with the power. Get a Pryo installed and then increase the fuel rate. That will make a hugh difference. You mentioned your were running about 35MPH. With the bigger tires your ground speed should be much faster than indicated. Someone else might know by how much.

 

[AMGeneral]

Ok,based on your description,it does have the correct non overdrive trans for a multifuel 5 ton.But since it does not start easily I would check your intank pump to see if it's working properly,the check the fuel filters.

If all is well with the fuel system,the check the air filter/cleaner for restrictions(dirty air filter or birds nest).

If it still seems under powered,it may just have the IP head worn out,as mentioned before install a pryometer and bump up the fuel SLOWLY,BUT DO not exceed 1100 deg exhaust temp!!

Just my opinions,I had a M51A2,but I yanked out the multi and converted it to a Mack ENDT 673 ,Power just isn't an issue any more.

 

[akexc]

I have a 67' M51a2 with 1100"s and I was thinking about the singles for it also. This fall I hauled 35K Shell corn to the mill, two wagons in tow. There are a couple small inclines and a freeway over pass between here and there. Low range high gear no problems. I would not want to create any problems with the bigger tires. I think the truck has the power if it is running right. What size tires are you running?

14.00R20s

 

[akexc]

akexc:

It sounds like your motor "may" be a little weak/wore out, it "should" start within 2-3 revolutions at the most in warm weather, YMMV in cold weather, and the black smoke should clear up once warmed up. (there will be a little)

5th gear should be all the way to the right and UP (if I remember correctly), this would indicate a overdrive transmission, and the correct one for a M51A2. If it shifts 5-th gear DOWN, I belive that indicates you have the transmission out of a gas engined 5-ton, WITHOUT overdrive, and all the wrong gear ratios for your multi-fuel engine.

If this is in fact the case swapping out to the correct overdrive transmission will probably solve most of your power/speed issues. I used to own a M52A2, and I'm pretty sure it shifted up and to the right for 5-th gear.

5th gear is back towards the seat. If I remember correctly, the tech manuals say that is the correct trans for an M51A2. But what you say could help explain my issue.

I am in the process of looking at an overdrive tranny.

 

[akexc]

Well, since my M51A2 never leaves the ranch, I can't really answer as to road speed. It does, however, have plenty of power for my use at 25 MPH and under. It sits on 395/85R20's (46").

From your pic, it appears your truck sits on 16.00R20's (53")--definately power killers.

Tires ar 14.00R20s.

 

[akexc]

Does it have the direct drive or overdrive transmission? If it has the latter, take out the overdrive transmission and install a direct drive transmission. You will lose some top speed (max speed will be about 46 MPH). On one hand, it sucks being able to ONLY drive at 46 MPH (now thinking about it, it might have been 47 MPH, but whatever). On the other hand, at least you will get to your top speed! I owned an M543A2 that weighed about what your truck weighed with the 10,000 pound load and that truck had plenty of power. The other killer...the tires as you have identified. These trucks are notoriously underpowered for road usage and you just killed it with those oversized tires. Take them off and put the 1100s back on. If you need aggressive tread and more traction, go with Michelin XLs, Firestones (can't remember the model #) or even Goodyear G177s.

The tires are 14.00R20s and unfortunately, I didn't change them out. They came on the truck, so not an easy fix.

 

[akexc]

If the engine is smoking all the time. There is a good chance the waste gate for the turbo is stuck in the open position. This lets the exaust gas bypass the turbine and go strait out the exaust. Causing a low boost condition. You also might check the injectors. Or at least run some cleaner through them. If they arn't spraying correctly you will end up with alot smoke and low power. I don't have a M51. But i do have a M52A2 with the same drive train. And pulling my loaded M127 it can get to 55MPH with no problems. It takes a while but it isn't unreasonable. If your still unhappy with the power. Get a Pryo installed and then increase the fuel rate. That will make a hugh difference. You mentioned your were running about 35MPH. With the bigger tires your ground speed should be much faster than indicated. Someone else might know by how much.

This is very helpful. I'll try to check all this out.

Thanks.

 

[akexc]

Ok,based on your description,it does have the correct non overdrive trans for a multifuel 5 ton.But since it does not start easily I would check your intank pump to see if it's working properly,the check the fuel filters.

If all is well with the fuel system,the check the air filter/cleaner for restrictions(dirty air filter or birds nest).

If it still seems under powered,it may just have the IP head worn out,as mentioned before install a pryometer and bump up the fuel SLOWLY,BUT DO not exceed 1100 deg exhaust temp!!

Just my opinions,I had a M51A2,but I yanked out the multi and converted it to a Mack ENDT 673 ,Power just isn't an issue any more.

Cool, more good info! I have replaced the air filter already, and have new fuel filters, but have not gotten to that yet. I'll work on checking out your suggestions.

Also, do you have a thread on the conversion you did to the Mack. Regardless of what I find, I still may be interested in doing a re-power.

Thanks.

 

[akexc]

An add to what AMG says. You may want to check the valves. You would be amazed at what a couple thousands of an inch can do to how an engine runs.

THanks, more good stuff to try.

 

[akexc]

THanks to everyone on this trread so far. All good helpful info.

Merry CHristmas!