550 lower transmission pressure in gear

[Davidkouns]

I bought a 83 550. After about an hour of running the dozer will quit pulling under it's own power. When you first start it it pushes great. After it cools back down it pushes great. I checked the pressure on the main port and I'm getting 90 psi in neutral and any where from 60 to 130 in gear. The neutral reading is within spec. The in gear is way low. I'm leaning towards the transmission pump or an internal leak in the selector valve. How could I go about narrowing it down to one or the other?

[LeonardL]

Hey sorry for the late response to your post. You have probably moved on by now. You say it is a 550 but what series do you have? It being an 83 I would assume it has the same transmission as the 450's with the HLR? Anyway a little more info might help a bit. Assuming this is the same transmission as the 450's with an HLR I do think you are on the right track as far as what is going on. The fact that it looses pressure at operating temps points to a weak pump, an internal leak or a bad regulator.

[Davidkouns]

It is a 550 c or also known as just a 550. I dont know if it's the same as the 450. It has low pressure as soon as you start it but it keeps dropping off the longer it runs. The transmission case has been replaced at one point in time no clue how long ago though.