Aisin downshift trouble

[Skram]

I'm still having issues with my 2014 3500 DRW CC Aisin transmission. I found one bad wiring repair behind driver side fender well and thought this was the problem.Repaired damaged wires but ended up in limp mode again when transmission tried shifting from 5th to 4th going up moderate hill with 5th wheel on the back. Doesn't always happen but got a PO73500 code this time. Where can I get a wiring diagram of the transmission circuits?

 

[transe]

I'm still having issues with my 2014 3500 DRW CC Aisin transmission. I found one bad wiring repair behind driver side fender well and thought this was the problem.Repaired damaged wires but ended up in limp mode again when transmission tried shifting from 5th to 4th going up moderate hill with 5th wheel on the back. Doesn't always happen but got a PO73500 code this time. Where can I get a wiring diagram of the transmission circuits?

You should be able to find wiring info by drilling down through the various menus at rambodybuilder.com. But P0735 is a Gear Ratio Error in 5th fault (indicating slippage within the trans), which is usually NOT a wiring problem. Does the fluid smell burned? Has the fault recurred? If it seems to drive OK now, then maybe you're only getting slippage under extreme conditions (5th wheel up a grade), and you might be able to just drive gently and avoid further issues. Just tap it down manually to 4th gear before hitting those grades with the trailer.

 

[Skram]

Thanks for the reply TransEngineer. This limp mode incident has not recurred yet and the transmission seems okay,fluid not burnt smelling. I've had all kinds of issues with the Aisin trans. This new one now has 3000 miles on it. I hear constantly how tough these transmissions are but I'm not seeing it. I was driving up a moderate hill with the trailer on and it downshifted 6th to 5th. Revs around 1600 in 5th and decreasing slowly. No more than half throttle. I'm not expecting a downshift so I was surprised when it let loose. Sometimes it will downshift when you expect and other times it just doesn't and let's the engine lug down. Could this be a TCM issue. Sometimes under towing load it acts like an automatic and other times it just doesn't shift when it should and you have to manually downshift going up hills. Recently going up a very steep(10%) grade it delayed 4th to 3rd and I had to manually shift and the same going 3rd to 2nd it just wouldn't downshift on it's own. Is this normal? I use tow haul and going down hills it downshifts as it should. No trailer on it shifts very smoothly.The previous transmission acted exactly the same but I had lots of solenoid related codes with it as well as going into limp mode when trying to downshift from 5th. I've read your previous posts about wiring issues and I've had all of them it seems. Limp mode, PRND display in yellow, jumping into neutral at times and having to hold pressure on the shift lever to stop it going into neutral. The new transmission so far just has the 5th to limp mode issue. Based on your posts I went looking for bad wires and found issues that I repaired. I'm going to open the harnesses back from all the plugs and check all the wiring just in case there are other covered up repairs but I'm starting to wonder with the slipping in 5th if these are just overrated gearboxes. I don't drive hard and I'm very light on the gas so why is this happening.

 

[Bob4x4]

There has been a number of flash updates for the Tcm over the years for improved shifting.There is nothing wrong with manually down shifting while towing,you may also notice better mpg when towing by taking control of the rpm

 

[sag2]

The likelihood of having two Aisin transmissions that are bad are slim to none, and slim just left. I would vote for the wiring or controller, but as Bob said have it flashed first.