So I checked the transmission fluid and it was barely on the dip stick. The manual said it holds 18 quarts (Allison). I put 4 in and now the district shows its over the fill line. Is that going to be an issue and if so is there a way to drain some out?
Yes, too high is as bad as too low.
Two methods: with a shop vac sucking on the transmission fill tube (duct tape "adapter"), remove the drain plug long enough to drain what you need to. QUICK is the operative here, but the suction from the vac will slow down the drain rate.
The other method is with a small pump (like one would use to take oil samples) through the dip stick tube.
I had my transmission to high and it was not happy and I drained it as Wolfe said with a small hand pump down the dipstick tube.
Are the U-series the same as the GV as far as fill tube length? I have a Detrot 6V92 pusher
I have a 6 1/4 gallon oil extractor that was purchased for special occasions such as this.
Harbor Freight model, many others available.
Quite a handy tool.