A750F Transmission issues (2 Viewers)

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Dec 3, 2021
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Location
Central Florida
Around 200k miles on my GX470 and for a year or so Ive been having a delayed shift from R and N into D. I replaced the drive shaft and it seemed to help a little, but the delay was still there from time to time. (I also flushed the trans fluid and replaced the filter about a year ago but the delayed shift was still happening before the flush. Fluid level is correct)

A month or so ago it started delaying the shift from 1st to 2nd occasionally, and when it did shift it was sometimes a hard shift.

Within the past week or so that delay has increased with higher rpms and seemed to be from 1st to 2nd and maybe 2nd to 3rd. Sometimes it wont shift and I have to bring the rpms down and up until it catches the next gear. Occasionally it throws me into limp mode now too.

Pulled a code P2714 Pressure control solenoid D stuck off. (SLT Solenoid) so I replaced that. Tested the old one and it was fine (5.6 ohms and worked with 12v applied)

No improvement with the shifting. Then threw another code.. P0771 solenoid E stuck off as well as the P2714 again.

I added half a bottle (12oz) of Lucas Stop Slip through the cooler hose after draining off a qt or so when it was warm....then mixing in the Lucas with it and pumping it back in. (-12oz).

I cycled R - D - R - D a bunch of times to get it through all the gears and for the rest of that day the problem was GONE! with a couple hours of driving around town.

The next day in the morning the issue was back but only when I first started driving, then it cleared up. Its definitely MUCH better, but still not gone completely. Id say 80% improvement.

Because the results were so immediate after adding the Lucas, would this indicate sticking valves? It claims to lube valves and ultimately revive seals (but that takes more time)

If it is the valves, can they be cleaned/flushed or do they get worn and will need a valve body replacement?

Thanks for any insight!
 
Updates:
The Lucas Stop Slip ultimately didn't help and the problems returned pretty quickly.

I ordered the Transgo valve body rebuild shift kit, reg boost valve and accumulator piston and did a full vb rebuild. Still ran like s*** when I was done.

I took it to a shop to hopefully get a specific diagnosis and they did a computer reset. After the computer relearned the new conditions of the rebuilt vb it runs great.

Hope this helps someone having similar issues I was having cause the VB rebuild is not expensive or very difficult either. Just be sure to reset the computer after!
 
Updates:
The Lucas Stop Slip ultimately didn't help and the problems returned pretty quickly.

I ordered the Transgo valve body rebuild shift kit, reg boost valve and accumulator piston and did a full vb rebuild. Still ran like s*** when I was done.

I took it to a shop to hopefully get a specific diagnosis and they did a computer reset. After the computer relearned the new conditions of the rebuilt vb it runs great.

Hope this helps someone having similar issues I was having cause the VB rebuild is not expensive or very difficult either. Just be sure to reset the computer after!
Glad you were able to resolve it. I have not heard of to many issues with the A750F.
 
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