Trans misbehaving

[JSchuricht]

Just got back from a 1300mi trip pulling ~15k that included several nasty mountain passes. Aside from loosing AC, leaking airbags and breaking a universal, my transmission is having an issue. While going down a steep windy grade, I attempted to manually put the transmission in 1st so I could lock the TC and engage the EBPV. I was able to move the shift lever into 1st without issue, but the truck acted as if I had placed it in neutral. 2nd worked fine. I tried 1st several more times during the trip with the same results. Several hundred miles later, I went to grab second for a light but changed my mind before moving the lever. When I stepped on the gas the truck acted as if I were in neutral even tho I was in drive with OD locked out. I pulled over, placed the truck in park and restarted the motor. Everything was back to normal. Then when I reached my destination, I decided to give 1st a try again and it worked.

OD light is NOT flashing and the highest trans temp was 210 but usually was around 180*. Was using a 40hp tow tune from DP.

Any ideas? Need to get this fixed ASAP.

[jesilvas]

How fast were you gong when you tried to put it into 1st? The truck won't actually engage first if you're going too fast for it. It's to save the trans. Also, you don't really wanna lock the TC in first.
Either way, I'd get it flushed. Get new fluid in it, and try it on stock setting next time it does it. See if somehow it could be the tune?

[JSchuricht]

Speed was my first thought too, but manual 1st wouldn't engage even at a stop. 1st would work fine when taking off in drive.

Can the column shifter be affected by the tune?

[jesilvas]

No it shouldn't. That's mechanical anyway isn't it?
Hopefully not a blocked VB?

[JSchuricht]

Pulled codes and checked fluid level today. Fluid is still full, possibly slightly darker than before but doesn't smell burnt.
p0733 gear 2 incorrect ratio
p0734 gear 3 incorrect ratio
p0743 torque converter clutch circuit electrical
p0093 fuel system leak detected large leak

Could it be a speed sensor screwing with things?

[powerhoghp]

The incorrect ratio codes, from a quick look around, suggests the truck asked for gear 2 but got something different, etc. Then a few posts suggested TPS problems. The fuel code can be from the gauge cluster having the fuel gauge drop rapidly.

[JSchuricht]

Not worried about the fuel code. Pasted it without paying attention. Besides, the gauge never drops blow 68psi.

Transmission is still baffling me. Read about some torx screws in the column that can loosen up and cause my issue but they were tight. Linkage looks good to my untrained eye.

[7.3550Duty]

It might also be that your mlps is acting up and telling your computer that its in a different gear than what your column is saying so you might wanna get that checked out at your local tranny shop if you can. Them do go out from time to time or you may just need it adjusted too