I'm the new owner of a 2010 Ram 1500 regular cab long bed ST model. According to the build sheet it doesn't have a limited slip differential. I tested it out from a dead stop on a grassy hill and it apparently just has one wheel drive. But, when I try the same hill at a slow moving speed--with the ESC engaged (it was also engaged while attempting to go up the hill from a dead stop) and accellerate, I see that both rear wheels are tearing up the grass as they spin and the resulting spin marks have the appearance of being created by a posi differential. I've searched the net and found no direct answer to this question and hope knowledgeable readers here can shed some light on things.

And on a different note and a question I've also researched and found no simple answer: The truck has a 4.7 ltr engine and 3.55 differential gearing. At what speeds would the auto transmission shift to the next highest gear-- at what road speed does overdrive engage during normal driving?
And, while I'm posting, I find the automatic headlight function to be extemely quirky when driving in low light in and out of shady areas. My other car which also has automatic headlamps exhibits none of the quirkiness re turning the lights on and off that I see with the Ram. Is this just poor engineering and normal, or is the unit defective?
TIA,
RC

 

there is some sort of brake actuated function in the esp which uses the brakes to act like a posi. essentially it slows the wheel thats spining with the brakes to force power to the wheel with traction.

cant think of what its called but rememeber seeing something and thinking...wish i had the real posi.

 

It's called traction control (Traction Control System) and part of the Electronic Stability Program (ESP) and works as you described as long as wheel speed is relatively slow. The vehicle is originally configured to start with the ESP activated each time the vehicle is started. When the ESP) switch is pressed the ESP is switch off and traction control is defeatured.

Regards,
Dusty

 

You have the 545RFE transmission and it is a six speed transmission. Prior to 2012 the 545RFE had two second gear ratios to smooth 4-2 kickdowns and operated as a sequentially shifting five speed:

1st gear = 3.00:1
2nd gear = 1.67:1 (1)
2nd gear = 1.50:1 (2)
3rd gear = 1.00:1
4th gear = 0.75:1
5th gear = 0.67:1


The vehicle speed at which the transmission shifts in to the next higher gear is determined by a number of factors, which include:

• Transmission Control Module (TCM) software shift schedule
• Throttle pressure
• Engine and transmission operating temperature
• Engine load

This transmission is fully electronic and fully adaptive, meaning the TCM continually remembers driver input and adjusts the shift schedule to perform to the driver's style, environmental and varying driving conditions.

545RFE Transmission Operation Based on ATF Temperature

ATF Temperature -16°F and below
With the transmission in the Drive position, the shift sequence will be 1st to 3rd until the ATF temperature reaches -12°F. When placing the gear selector in either 1st or 2nd gear the transmission will be in 2nd gear only. There will be no torque converter lock up and switching off Overdrive or Tow/Haul Mode will have no effect.
ATF between -12°F and -10°F
The transmission shift sequences are as follows:
· No torque converter lock up
· No shift in to 5th gear
· Delayed 2-3 upshifts
· Delayed 3-4 upshifts
· High speed 4-2, 3-2, or 2-1 kickdown shifts are prevented
· High throttle opening shifts will be early
· Switching off Overdrive or Tow/Haul Mode will prevent shifts into 4th gear
ATF between -10°F and 36°F
The transmission shift sequences are the same as above, except that 2-3 upshifts are not delayed. Switching off Overdrive or Tow Haul Mode will prevent shifts into 4th gear
40°F and 80°F
All shift sequences are normal except there will be no torque converter lockup. Switching off Overdrive or Tow/Haul Mode will prevent shifts into 5th gear.
80°F and 240°F
This is normal operating fluid temperature. The 545RFE will be in the normal shift sequence, including allowing torque converter lockup.
240°F ATF or engine coolant at 244° F
The transmission shift sequences will be as follows:
· delayed 2-3 upshift
· delayed 3-4 upshift
· 3rd gear FEMCC from 30-40 MPH
· 3rd gear PEMCC above 35 MPH
· Above 25 MPH the torque converter will not unlock unless the throttle is closed or if a wide open throttle, 2nd gear PEMCC to 1 kickdown is made.

EMCC = Electronically Modulated Converter Clutch
NO EMCC = No Electronically Modulated Converter Clutch
PEMCC = Partially Electronically Modulated Converter Clutch
FEMCC = Full Electronically Modulated Converter Clutch
Gradual to No EMCC = Gradual to No Electronically Modulated Converter Clutch

Hope this helps.
Regards,
Dusty

 

Isky and Dusty,
Thank you both for your considered and knowledgeable replies. Both replies provided excellent and useable information.

I really wonder why Dodge would persue a complicated traction control system whilst not providing as standard a limited slip differential that would go a long way towards achieving their ends of controlled driving and traction.
As a side note, I have a BMW M car that has both--DSC and posi-- and it is a joy to drive and creates a much more safe driving experience (and needless to say, when the DSC is disengaged it is one slippery monster).
Rusty

 

Actually, my 2010 Ram has both traction control, which was standard on the Big Horn package, and limited slip, which was an option with the 3.92 axle.

I think you'll find that traction control on Fords and GMs are usually found without limited slip as well.

Regards,
Dusty.