Transmission

[Nathaniel Becker]

I have a 04 Ram with the 545rfe transmission, it has 255,000 miles. It lost overdrive a few thousand miles ago and my gas mileage has decreased a bit. The trans has the original fluid so I was wondering if y'all thought changing it could possibly fix the problem. Any help is appreciated, thanks.

 

[ST-8]

If it’s the original fluid with that many miles, I’d be looking for a junkyard trans to swap in. Wouldn’t waste my time an money on it, changing the fluid ain’t bringing o/d back.

 

[HemiLonestar]

Did you lose both OD gears or just 5th (both 4th and 5th are OD gears)? Regardless, fluid change ain't bringing it back. You should have a few codes though...

 

[Fast69Mopar]

I have a 04 Ram with the 545rfe transmission, it has 255,000 miles. It lost overdrive a few thousand miles ago and my gas mileage has decreased a bit. The trans has the original fluid so I was wondering if y'all thought changing it could possibly fix the problem. Any help is appreciated, thanks.

I can't believe that it still had the original factory fill in the transmission. Are you the original owner of the truck?

You said you lost overdrive? 4th and 5th gears are overdriven gears. 4th gear has a 0.75:1 ratio and 5th gear has a 0.67:1 ratio.

Are you saying that your trans is only shifting from 1st to 2nd to 3rd?

Or is it shifting 1st to 2nd to 3rd and 4th but not shifting into 5th?

What RPM are you cruising at running down the highway? Are you cruising over 3,000rpm or is is about
2,000-2,100rpm?

This will help me in providing you with what path to take.

 

[Smokeybear01]

It almost sounds like an electrical issue, nothing to do with trans fluid. If you put it in tow/haul you would get the same effect, but it should reset when you shut the truck off. (the tow/haul button on the end of the gear selector knob) Seems strange if you're not throwing any codes.

 

[Nathaniel Becker]

I lost 5th gear, at 55mph it's at about 2,000 rpm
The truck was purchased used at 17,000 miles
It was my dad's work truck then passed down to when he got a newer truck
He never was able to maintain anything on it

The truck has so many codes the guy at the auto parts store seemed a little overwhelmed and didn't give me them all

@Fast69Mopar
@HemiLonestar
@Smokeybear01

 

[Fast69Mopar]

I lost 5th gear, at 55mph it's at about 2,000 rpm
The truck was purchased used at 17,000 miles
It was my dad's work truck then passed down to when he got a newer truck
He never was able to maintain anything on it

The truck has so many codes the guy at the auto parts store seemed a little overwhelmed and didn't give me them all

@Fast69Mopar
@HemiLonestar
@Smokeybear01

When you were looking at the DTC's that were set was one of them a P0735 Gear ration error in 5th?

If the trans doesn't shift into 5th gear we would look at the O/D Clutch and the 2C Clutch. But, and a big but, since we have 2nd gear that would tell us that the 2C clutch is at least operational in some capacity. Also, since we have 3rd and 4th gear that would tell us that the U/D Clutch and the O/D Clutch is working to get us into 3rd gear and that the O/D Clutch and the 4C clutch is at least operational in some capacity as well to get us into 4th.

Its time to get a scan tool hooked up to this thing. I would only recommend a dealer at this time so the RFE Simulator can be connected to the truck to test the PCM and the wiring. The RFE Simulator connects in place of all of the transmissions electrical connectors. With the scan tool connected and the RFE Simulator connected at the same time we can test the outputs from the PCM to see if the PCM is telling the transmission to do the correct things.

 

[Nathaniel Becker]

That hurt my brain
Thanks
@Fast69Mopar

 

[Fast69Mopar]

That hurt my brain
Thanks
@Fast69Mopar

Sorry for the technical fundamentals of the RFE transmission.

 

[Marley]

255K with no service ?
Any fluid/filter change at this point would be pointless and prolong or promote the inevitable. Imo

 

[HemiLonestar]

255K with no service ?
Any fluid/filter change at this point would be pointless and prolong or promote the inevitable. Imo

Been my experience that a fluid and filter change is never bad; for god's sake by that point don't flush it though.