RPM @ 75 MPH?

[josie jarrett]

2014 6.4 2500 4X4 WITH 3.73 GEARS we think what should the 6.4 be turning at 75 mph? Also how do I confirm the gear ratio on a Dodge pickup?

 

[Bigseff23]

I have 35 and 3.73 and I'm around 1900ish

 

[josie jarrett]

I think they are 3.73 not sure just got the truck but turning over 3000rpm @ 75mph. I think its staying in 4th gear. Any idea what the final drive ratio on a 6 speed automatic transmission is?

 

[sandawilliams]

Tap the gear selector down once and it will tell you what gear you are in on the evic screen.

 

[crash68]

I think they are 3.73 not sure just got the truck but turning over 3000rpm @ 75mph. I think its staying in 4th gear. Any idea what the final drive ratio on a 6 speed automatic transmission is?

Using 33" tires and 3.73 axle ratio:
6th is .67 (1925 rpms @ 75)
5th is .75 (2150 rpms @ 75)
4th is 1:1 (2850 rpms @ 75)

 

[josie jarrett]

Just made a cold pass 1900 at 75 drove 15 miles turned around shifted normal 1st through 3rd hard shift into 4th never shifted again. Pulled over killed engine waited about 30 seconds lit it back up and 1st through 3rd normal hard shift into 4th never shifted again. Any ideas?

 

[olyelr]

Just made a cold pass 1900 at 75 drove 15 miles turned around shifted normal 1st through 3rd hard shift into 4th never shifted again. Pulled over killed engine waited about 30 seconds lit it back up and 1st through 3rd normal hard shift into 4th never shifted again. Any ideas?

So it's not shifting over 4th? Does it still downshift through the lower gears like normal?

 

[HammerHead]

Just made a cold pass 1900 at 75 drove 15 miles turned around shifted normal 1st through 3rd hard shift into 4th never shifted again. Pulled over killed engine waited about 30 seconds lit it back up and 1st through 3rd normal hard shift into 4th never shifted again. Any ideas?

Your truck is in Limp Mode; this happened to me and I had to get it to the dealership immediately. No warning lights on the dash but it was showing code errors once the dealership looked at it.

 

[mtofell]

Yeah, for whatever reason the tranny doesn't always trigger CELs when things go wrong. Mine completely self destructed and I had to drive a few miles to get off the freeway to a safe spot. It was revving, clunking, burning..... you name it, it was doing it but NO lights. Finally, as I was backing into a parking lot (lost all forward gears) a light came on.

 

[josie jarrett]

I dont know if its shifting back down. But when I come to a stop and back to speed it shifts up to fourth. I'm a little afraid to drive it to much I live a couple of hours from the dealership and it sounds like I may need to get it back there

 

[josie jarrett]

Yeah, for whatever reason the tranny doesn't always trigger CELs when things go wrong. Mine completely self destructed and I had to drive a few miles to get off the freeway to a safe spot. It was revving, clunking, burning..... you name it, it was doing it but NO lights. Finally, as I was backing into a parking lot (lost all forward gears) a light came on.

Oh crap! Was there any indication that you had trouble before it self destructed ?

 

[mtofell]

Oh crap! Was there any indication that you had trouble before it self destructed ?

Other than the poor shifting and poor gear spacing, no That stuff just comes with every 66rfe Ram tranny.

No, mine just blew up while sitting in stop/go traffic. No load, no towing. Traffic sped up, I hit the gas, the tach went way up, I barely moved. At the end of the day was a total fluke thing and likely totally different than what's going on which your tranny. The tech that torn it down said the valve body just blew apart and ripped up the whole transmission.

 

[josie jarrett]

Other than the poor shifting and poor gear spacing, no That stuff just comes with every 66rfe Ram tranny.

No, mine just blew up while sitting in stop/go traffic. No load, no towing. Traffic sped up, I hit the gas, the tach went way up, I barely moved. At the end of the day was a total fluke thing and likely totally different than what's going on which your tranny. The tech that torn it down said the valve body just blew apart and ripped up the whole transmission.

How do I tell if mine has a 66rfe tranny?? I literally just bought the truck last Monday to pull my 3H weekender gooseneck with and don't know anything about Dodges...but I killed the Chevy and had to have a truck fast! Overall do you like yours? Are there any other problems especially with towing I should look for? Mine has 142,000mi on it is that going to be a problem ? This is my first gas burner in a long time also..and thank you very much for your help!

 

[Nickx86]

If you have a 3/4 and 1 ton gasser, you have the 66rfe transmission. if you have a 3/4 ton and lower output 1 ton diesel, you got a 68rfe transmission. If you got a 1 ton w a high output diesel then you have the Aisin transmission.

 

[madweazl]

You can add your vehicle to MOPARs site and it will show you everything on the truck from the factory (including rear gears).

 

[thomas5853]

At 75mph with a 3.73 and stock 20 in rims my RPM is about 1700.

Sent from my SM-N950U using Tapatalk

 

[SouthTexan]

RPM = (Axle Ratio x Vehicle Speed in mph x Transmission Ratio x 336.13) / Tire Diameter in inches

1 2 3 4 5 6
66RFE - 3.23 /1.84 /1.41 /1.00 / 0.816 / 0.625

Stock tire diameter for 4x4 trucks is 33.3" for 18" rims and 33.4" for 20" rims.

 

[josie jarrett]

If you have a 3/4 and 1 ton gasser, you have the 66rfe transmission. if you have a 3/4 ton and lower output 1 ton diesel, you got a 68rfe transmission. If you got a 1 ton w a high output diesel then you have the Aisin transmission.

I have a 3/4 ton with a 6.4 Hemi so it has a 66rfe?

 

[Nickx86]

I have a 3/4 ton with a 6.4 Hemi so it has a 66rfe?

Correct, unless you got a 2019 then it’s the zf 8hp75

 

[josie jarrett]

You can add your vehicle to MOPARs site and it will show you everything on the truck from the factory (including rear gears).

Oh cool thank you very much!!