95 Gulfstream with a 6 speed allison auto (350 cummins) 85K miles. About a month ago did a 1000 mile trip with steep hills (WV) and the RV ran flawlessly. Yesterday taking it on a short run to the lake for the weekend (about 60 miles) all flat terrain and got the do not shift warning buzzer in 5th gear. Pulled over, reset the ignition (turned off and back on) and it went away. About 2 miles down the road, same thing hit 5th gear and got the do no shift warning. Temps were fine (water and trans) Pulled over again - Read the code 55 87 Clear the code out and called the tow truck (short tow since we are close to home) While waiting for the tow truck - I noticed that I code get the code every time if I put it in D move forward a couple of feet, stop, select N then go to R and while backing up I would get the same DNS warning light. Tow truck shows up - finds a couple of the battery cables loose on a solenoid located on the frame rail in front of the trans on the drivers side. Said that may be causing the issue (power cutting out to the controller) - we tightened them down and it seemed to go away. Drove it for about 10 more miles with no issues then got the DNS light again in 5th but different code 32 55 (C3 pressure switch in open in 5th) I parked it and just had it towed to the shop We haven't owned this particular RV very long but it appears to have been taken care of. Runs strong, shifts nicely, no leaks, drives very easily but this warning issue has me perplexed. Any guesses?