M1152 Low Top Speed

[01GRANDER]

pulley size definitely affect it.
The earlier trucks used a drive off the oil pump for the tach.
With the turbo on there there is no room for that drive, so instead it takes a signal from the generator, and since that's belt drive, changing the pulley size affects how fast the generator spins and screws up the tach signal.

Not something you really think about until you're affected. I'm just glad Coonass77 chimed in with the answer you were looking for.

As for top speed, they aren't really made to go fast. As it is, once you get the tach straightened out, you're talking a top speed over 70mph easy, and reports have doing over 80 no problems.

Thanks for the help. Hopefully the larger pulley isn’t too expensive or I might just have to get one of those tiny tachs. It would just be nice to verify some other way so I don’t accidentally blow my engine. It makes sense but I need to verify.

What point could I use with one of those gauges to measure rpm’s? I assume a lot of the pulleys aren’t spinning at engine rpm’s or I mean, they are different sizes.

 

[Coug]

Thanks for the help. Hopefully the larger pulley isn’t too expensive or I might just have to get one of those tiny tachs. It would just be nice to verify some other way so I don’t accidentally blow my engine. It makes sense but I need to verify.

What point could I use with one of those gauges to measure rpm’s? I assume a lot of the pulleys aren’t spinning at engine rpm’s or I mean, they are different sizes.

if it was me I'd do it from underneath the truck, aimed at the crankshaft pulley. That's pretty much the only thing that is guaranteed to be at crankshaft speed.

 

[01GRANDER]

if it was me I'd do it from underneath the truck, aimed at the crankshaft pulley. That's pretty much the only thing that is guaranteed to be at crankshaft speed.

Got it. I’ll order that gauge and confirm that way. Appreciate the help.

 

[Action]

There is already an rpm sensor on the crankshaft.

 

[Retiredwarhorses]

Guys, the 400amp uses either a fixed pulley “smaller”or the “Clutching“ pulley just depends on what you got from
auction. I’ve found it’s hit or miss what you get, The clutch pulley is larger, thus the indicated rpm’s is lower.
Reason is simple for smaller pulley , The Gen puts out 185 amps at idle, that’s almost max what a 200 puts out.
All this is for C&C truck, shelter trucks, that’s the reason for the tachometer as well…long long high idle times.
i suspect this is also the reason for so many bad turbos and collapsed catalytic converters I’ve seen on these variants.

 

[Action]

Dude, no reason to be like that. Seriously, don’t be that guy. I have a m998, I already have a 6.5.

In post #3, you said it is definitely not running at 2700 rpm.
In post #21, you said you are almost certain the engine is right at redline.
I assume you are making these statement based on the sound of the engine. That wont change with a different pulley. The engine will still be running the same.
And, the clutch pulley from the 200 amp alternators is hundreds of dollars.

 

[01GRANDER]

In post #3, you said it is definitely not running at 2700 rpm.
In post #21, you said you are almost certain the engine is right at redline.
I assume you are making these statement based on the sound of the engine. That wont change with a different pulley. The engine will still be running the same.
And, the clutch pulley from the 200 amp alternators is hundreds of dollars.

It’s subjective but your comment was rude.

 

[01GRANDER]

Guys, the 400amp uses either a fixed pulley “smaller”or the “Clutching“ pulley just depends on what you got from
auction. I’ve found it’s hit or miss what you get, The clutch pulley is larger, thus the indicated rpm’s is lower.
Reason is simple for smaller pulley , The Gen puts out 185 amps at idle, that’s almost max what a 200 puts out.
All this is for C&C truck, shelter trucks, that’s the reason for the tachometer as well…long long high idle times.
i suspect this is also the reason for so many bad turbos and collapsed catalytic converters I’ve seen on these variants.

So which one is accurate? It’s saying I’m redlining at 63-65 and idling at 950rpms. This is mine, if it’s accurate then I have bigger problems, I was hoping that it was just my pulley causing it to not be accurate as mentioned in another thread.

 

[Mogman]

What is telling you you are red lining it?? unless it really jumps when you put it in gear it probably is not idling at 950RPM, looks like a small pulley to me.
If it is the tach that is telling you it is red lining it than it is probably the SAME issue.

 

[Mogman]

Just put he hammer down, the IP has a governor and should not let it blow up!!!
At least not right away!

 

[Coug]

measure the diameter of the pulley.

To me it looks too small, but without a good size reference we could be wrong.

 

[01GRANDER]

measure the diameter of the pulley.

To me it looks too small, but without a good size reference we could be wrong.

It is the smaller fixed pulley, not the clutch one. I asked someone which is more accurate in relation to the engines rpm’s and they wouldn’t exactly say. I assume the larger clutch one is more accurate and the smaller one makes it look like it’s higher rpm’s. I wont know until I figure out how to measure the rpm’s.

I did order one of those contactless scanners, hopefully it will give me a ballpark of my actual rpm’s

I am looking at another tach, you add some magnets to the crank shaft pulley and mount a sensor with a slight gap. Not sure how well it will hold up over time though

 

[Retiredwarhorses]

It is the smaller fixed pulley, not the clutch one. I asked someone which is more accurate in relation to the engines rpm’s and they wouldn’t exactly say. I assume the larger clutch one is more accurate and the smaller one makes it look like it’s higher rpm’s. I wont know until I figure out how to measure the rpm’s.

I did order one of those contactless scanners, hopefully it will give me a ballpark of my actual rpm’s

I am looking at another tach, you add some magnets to the crank shaft pulley and mount a sensor with a slight gap. Not sure how well it will hold up over time though

smaller pulley will yield higher rpm’s than a larger pulley, there are only 2 pulleys.
a quick trip to the proper TM would yield results.

 

[Action]

It is the smaller fixed pulley, not the clutch one. I asked someone which is more accurate in relation to the engines rpm’s and they wouldn’t exactly say. I assume the larger clutch one is more accurate and the smaller one makes it look like it’s higher rpm’s. I wont know until I figure out how to measure the rpm’s.

I did order one of those contactless scanners, hopefully it will give me a ballpark of my actual rpm’s

I am looking at another tach, you add some magnets to the crank shaft pulley and mount a sensor with a slight gap. Not sure how well it will hold up over time though

For the third time...there is already an rpm sensor on the crankshaft.

 

[Retiredwarhorses]

One of the more confusing pages of the install of a 400amp…”if you already have a pulley, install it”, as far as I know, only the clutch pulley is and was ever used on ECV 200amp’s, so no mention of how that smaller fixed pulley got introduced.
Also, for anyone installing a cLuther pulley, the center nut is different for a 400 than it is for a 200, they are not compatible.

 

[TOBASH]

Guys, the foundation here is the differential gearing. Ones the OP determines the gearing, he will have an answer, re.: is the tranny slipping or not properly shifting and locking up.

Alternator pulley size is a non-issue.

Action has clearly pointed out the RPM sensor on the crank.

 

[Retiredwarhorses]

Guys, the foundation here is the differential gearing. Ones the OP determines the gearing, he will have an answer, re.: is the tranny slipping or not properly shifting and locking up.

Alternator pulley size is a non-issue.

Action has clearly pointed out the RPM sensor on the crank.

indicated RPM’s and pulley size is a major factor, I’ve already done this circle jerk over a year ago.
The diffs are 3.08, thats the only diff used in an ECV…its not an unknown.

 

[TOBASH]

indicated RPM’s and pulley size is a major factor, I’ve already done this circle jerk over a year ago.
The diffs are 3.08, thats the only diff used in an ECV…its not an unknown.

Yeah, you’re correct Steve. My point is the conversation has gone full circle. He needs to identify the “true” RPM and then confirm if there is a problem or if it is his perception that he has a loud engine.

 

[Mogman]

For the third time...there is already an rpm sensor on the crankshaft.

OK what if he does not have a Tech II to read it with? BTW that is an inductive pickup and it runs 4X crankshaft speed.
All he needs is a pulley to fix his tach issue easy pleasy fix, RWH has pointed that out,, then he can tell if the trans is acting correctly or not.

 

[Retiredwarhorses]

Here is what I know, anyone who owns or owned an A2 truck ”2.73” and than hops into a ECV/REV truck, will immediately think they are missing the overdrive gear…