funny info about new LLY duramax

[DIESELMAN]

Originally posted by Prairie Dog

Mopar Mudder, haven't you ever noticed how weak acceleration in 2nd gear is compared to 3rd? I'm not sure how they do it either but I have found an odd looking thing or two attached to the transmission. There's a black plastic line of some sort that I've never seen on a manual trans before. Anybody know what I'm talking about here?

BTW It's even more evident w/ a fueling box.



Scotty

PDog - do you roll it or just toss it into your pipe What Line, I do see the reverse switch lines but thats all I see... ...



DM

 

[KBennett]

Manually speaking the computer could easily look at engine RPM and MPH to determine what gear you are in. The only thing it would have to guess at is the diff ratio but that would be a small difference in the map.

 

[DIESELMAN]

Its actually simpler than that... .



Divide RPM by Pulse Rate of the Speedo sensor and you get the current ratio, ie 1400 RPM / 246. 6 Pulses per minute gives you 5. 63, first gear.



The MPH requires a correction for both rear dif and wheel diameter, the PPM out is uncorrected and in proportion to engine RPM and gear.



The ECM doesn't care what the speed is, or the diff ratio or anything else, there is probably a simple de-rate curve based on the transmission out to RPM ratio, or a simple +/- table based on the transmission info which is entered as well.



At least thats what I would do.....

 

[RLaux]

my brother has the lly with allison transmission and i cant tell that there defueling it in 1st and 2nd at 24000 lb combo it gets right into 3rd gear really fast pulls prety hard. goes into overdrive and stays there . thats average rolling hills. he doesnt use the tow haul because it uses to many rpms for nothing but wasted fuel. I have ordered the new 600 cummins, cant wait to compare these trucks

 

[MCummings]

Better not slip the clutch any... ... .



Drove my buds '04 (305HP) and yes, 3rd gear felt stronger, but that's only because I was all out of RPM before I had enough boost in 2nd gear.



If you are at a stop, and run the motor up to 1,900 and let the clutch ou while at WOT, then 2nd will feel much stronger than 3rd if you can keep traction.



My '98 6-speed only has a sensor for reverse gear.



Merrick

 

[Bill Stockard]

Originally posted by Punkineater

Might as well give Ford and GM their transmissions. We definitely have the upperhand with the Cummins, but the Dodge automatic is pure crap and always has been. Guaranteed if Dodge inked a contract with Allison tomorrow you guys would be drooling at the chops to own an Allison over your 48RE or 47RE.

Yes, I would jump at the chance to get an Allison 5/6 speed 3000 series in our trucks, but it ain't gonna happen... too big, heavy, and expensive for a pickup. I had just as soon have the 48RE as the Allison 1000 series, which is a poor example of Allison design and engineering.



Bill

 

[Mopar_Mudder]

Originally posted by Prairie Dog

Mopar Mudder, haven't you ever noticed how weak acceleration in 2nd gear is compared to 3rd? I'm not sure how they do it either but I have found an odd looking thing or two attached to the transmission. There's a black plastic line of some sort that I've never seen on a manual trans before. Anybody know what I'm talking about here?

BTW It's even more evident w/ a fueling box.



Scotty

No kinda the opposite. Put a big load behind it, talking like 30,000 gross and 2nd feels maybe a little stronger then 3rd, my clutch tries to slip in 2nd but never in 3rd. I think the thing you are feeling in 2nd empty is the fact that it winds up so fast to the shift point that it never creates full boost and give you that through in the seat feel. When you shift to 3rd their is more load on the engine and it can create more boost.

 

[Tomeygun]

Originally posted by Mopar_Mudder

No kinda the opposite. Put a big load behind it, talking like 30,000 gross and 2nd feels maybe a little stronger then 3rd, my clutch tries to slip in 2nd but never in 3rd. I think the thing you are feeling in 2nd empty is the fact that it winds up so fast to the shift point that it never creates full boost and give you that through in the seat feel. When you shift to 3rd their is more load on the engine and it can create more boost.

Good example, because my direct drive gear (4th) feels the strongest... just floor it at 1200 RPMS and it puts you in the back seat... 5 does the same, but wind drag is a bit high to feel SOP power



CYA

 

[MCummings]

Originally posted by MCummings

3rd gear felt stronger, but that's only because I was all out of RPM before I had enough boost in 2nd gear.

Merrick

 

[Mopar_Mudder]

Originally posted by MCummings





Merrick

Amen

 

[BRayls]

I played all the way to work and back today,I think mopar_mudder is correct,you just cannot get full boost in 1st,2nd gear. you have to shift up to quick.