I purchased a JD 670A grader with 8 speed PS transmission problem. I think the problem is in C1 or C2. What it does, in the gears 1-6 ( below 7 and 8) is when you place it in and gear and put travel selector in forward or reverse it moves with clutch petal hyd valve disengages (pedal down) and when you release clutch hyd valve (pedal up) it loads down the engine. Previous owner said he checked shift valves. I will confirm C1 & C2 pressure check. I think ether C1 or C2 have a blow clutch pack with locked up disk or the metal seal ring is broken that supplies oil pressure to C1 or C2.
Yes, but you would have to pull the transfer drive. I would do some thorough testing before going through all that work.
Thank's for the info, I see I would need to support the engine. I will do 4 gauge pressure check.