Lock up occurs when od is on but no 4th gear
 

Please help , rebuilt trans , no 4th gear , tried the pot mod , grounding the brown wire with a toggle nothing . It did go into 4th but very randomly , seems like on really cold days before the temp gauge moved , anyone ? New overdrive switch , with overdrive on it won't lock up until about 50mph but never shifts into 4th

Anyone with any info or advice please chime in

Sounds like a TPS issue

Even with the pot mod ? The truck locks up at around 50 55 but 4th doesn't happen , just trying to make sense of it

NO 3-4 UPSHIFT
1. O/D Switch In OFF Position.
1. Turn control switch to ON position.
2. Overdrive Circuit Fuse Blown. 2. Replace fuse. Determine why fuse failed and repair as necessary (i.e., shorts or grounds in circuit).
3. O/D Switch Wire Shorted/Open Cut. 3. Check wires/connections with 12V test lamp and voltmeter. Repair damaged or loose wire/connection as necessary.
4. Distance or Coolant Sensor Malfunction. 4. Check with DRB® scan tool and repair or replace as necessary.
5. TPS Malfunction. 5. Check with DRB® scan tool and replace if necessary.
6. Neutral Sense to PCM Wire Shorted/Cut. 6. Test switch/sensor as described in service section and replace if necessary. Engine no start.
7. PCM Malfunction. 7. Check with DRB® scan tool and replace if necessary.
8. Overdrive Solenoid Shorted/Open. 8. Replace solenoid if shorted or open and repair loose or damaged wires (DRB® scan tool).
9. Solenoid Feed Orifice in Valve Body Blocked. 9. Remove, disassemble, and clean valve body thoroughly. Check feed orifice.
10. Overdrive Clutch Failed. 10. Disassemble overdrive and repair as needed.
11. Hydraulic Pressure Low. 11. Pressure test transmission to determine cause.
12. Valve Body Valve Stuck. 12. Repair stuck 3-4 shift valve, 3-4 timing valve.
13. O/D Piston Incorrect Spacer. 13. Remove unit, check end play and install correct spacer.
14. Overdrive Piston Seal Failure. 14. Replace both seals.
15. O/D Check Valve/Orifice Failed. 15. Check for free movement and secure assembly (in piston retainer). Check ball bleed orifice.

Full post can be found here 47RE transmission troubleshooting chart. - Dodge Cummins Diesel Forum

I've gone through almost all of these except for a couple , can anyone tell me where the overdrive fuse is ? I didn't even know there was one

It should be fuse number 11 in the under hood fuse block. Also, try unplugging your O/D button in the dash and see if anything changes.

I've been through the headaches of diagnosing these transmissions and have learned a lot along the way. I'll help you anyway I can, I know how frustrating these things can be.

Happy Thanksgiving!

Thank you very much and happy thanksgiving !! I'll unplug it and go for a test drive too , then I'll also check the fuse 11 under the hood , is there anything else I could do or possibly check , thank you again - Jason

Are you familiar with checking the codes on these trucks?

http://dodgeram.info/Engine-Gas/OBDI/pcm_fault_code.htm

How long ago was the transmission rebuilt? Did you have it rebuilt or was it done by the previous owner?

Here is the component application chart for the 47RE

https://cimg7.ibsrv.net/gimg/www.die...c58e14540d.jpg

I was trying to edit the above with this information but it timed out.

Are you familiar with checking the codes on these trucks?

PCM Fault Codes

How long ago was the transmission rebuilt? Did you have it rebuilt or was it done by the previous owner?

Below is the component application chart for a 47RE, it can be used to help pinpoint the source of a problem with the transmission.

https://cimg7.ibsrv.net/gimg/www.die...c58e14540d.jpg

Pay attention to the OD-4th column. For OD to function it requires the Front Clutch, Rear Clutch, and OD clutch to be on. Notice how those components overlap to the other gears. If the Front Clutch is not functioning you will not have Reverse, 3rd, or OD. If the Rear Clutch is not functioning you won’t have 1st, 2nd, 3rd, or OD. The OD Clutch however only affects OD.

If your only issue is a non functioning OD then the problem is with the components that cause the OD clutch to be applied or the OD clutch itself. Personally I believe it’s a malfunctioning OD solenoid. Check for codes using the above link and let me know what you find.