Right, so its a 1960's era <MF50A Industrial tractor with the Perkins 203 and a loader on the front. It is the instareverse type with the torque converter and shuttle shift. Until recently, it has run well and the engine continues to perform but while doing some digging the other day, it suddenly lost forward and rearward drive. I tried a few combinations of gears but nothing and it almost feels like it is stuck in idle. I was able to get it to roll out of the way using the bucket to drag it forwards and backwards but now I am trying to figure out what went wrong. My guesses and rebuttals are: Snapped selector - It could be the Hi/Lo selector has snapped and been left in idle. I am unsure on this one as when I look through the trans filler, I can see the shaft moving at the front so know the linkage is working and that would mean it is the rear part that snapped. Am trying to get into the rear box to see with a bore scope but that is proving difficult. I also wonder if this is the case as when I use the 1/2 gear, I see the gears spinning through the filler as well hence, are these two exclusive or connected? I can test this with putting the Hi/Lo in neutral and then shifting 1/2 into gear and see what changes. Torque converter - If this has blown, then would I still see gear spinning in the trans filler but no load applied to the rear (eg. just through a bit of friction is it able to turn the gearing?) I am thinking this is unlikely but a possibility. Can confirm this with a view of the output shaft in the transmission inspection hole. Could it be low on oil? How would I test that? Forward and rearward clutch packs - Doubtful as if I had failed one or the other, then I would still have a forward or reverse gear. But the oil feed to them could be an issue hence the next idea Transmission oil pump - Not sure about this one. I wonder how I would test this and again assume that it would be the output shaft turning which would tell me if it is working or not. I also wondered about it being low on oil but the dipstick said it was fine. Rear diff - Unlikely given that it was rolling freely in gear and I heard no crunching noises at the time it stopped. This however would be the next location to look if that output shaft is turning. Shuttle valve - If this managed to bypass somehow then I would have neither forward or reverse. I am unsure on how to inspect/test this though however I did manage to check that the pedal linkage was actuating all the way into the trans case just to make sure it wasnt something stupid like that. I really hope I don't have to split the tractor on this one as would have to do it out in the paddock with removing the cab and the loader attachment. So wanting to run through the easiest to hardest bits that I can diagnose first to work out why the hell it wont run.... So what I am thinking is: Inspect through the side covers to check the Hi/Lo gear is actuating and that the output shaft is working. If no output shaft, then looking further back up by removing top of gearbox cover (which is a pain as have to remove the steering box, fuel tank etc. If the gears look ok from there, will have to determine if it is the torque converter somehow or whether it is the transmission pump not supplying the clutch packs. Any other ideas for some simple ways to rule these things out would be appreciated.
Of note as well is that the PTO turns at the back. I also tested the hi/lo and 1/2 combination and the 1/2 shift will run whether the Hi/Lo is in gear or not. So still could be the selector on the Hi/Lo Need to get into that inspection cover and see if it is the output shaft (Shear Tube)!
I'm not familiar with a model with a PTO, that could be what you're seeing moving, I don't know. I'd think the PTO would usually be lower in the transmission case. Those reversers like to shift a little tricky, like you have to be at just the right point to shift it between any gears without grinding. How did yours operate before it broke? and can you get any gear grinding if you shift it right after removing your foot from forward or backward pedal? Have you tried the differential lock? Do you have a manual? are you looking at the correct dipstick? seems there was some change over the years on where the fluid was checked, but it's different from the transmission as far as I can recall. Otherwise, I think you're on the right track.
Used a bore scope down the standpipe on top of the gearbox and managed to confirm the Hi/Lo is engaging correctly. That's one thing off the list to check. Next will be to check out the shear tube via the inspection hole on the side to see if I can spot a break.
MF50A is from late 60's to early 70's. Instant reverse was used for decades though on a lot of different machines. I have a book that explains how it works but doesn't have any trouble shooting. It was made by Funk.
Thanks for the response, I typically dont shift while running because of that issue. If it has not come to a standstill, you can feel it trying to pick up the gears while moving. The diff lock was disabled on mine a long time ago so havent tried that at all. might be something to consider though. I have a manual for both repair and operations but they're not overly helpful. And yes, I am at the dipstick which is labelled "Transmission" that takes a reading on the side of the circle hatch. I also don't believe it is a pump issue as the standpipe blew oil out when I opened it up so plenty of pressure in there. Again, I think next step is to open that circle hatch on the side of the gearbox and check the shear tube. Maybe too much ground engaging overloaded it and if that is the case, I think it would be a relatively simple fix (eg. not splitting the tractor) so I really hope it is that... Will find out this afternoon as I couldnt get the bore scope to pick it up down that standpipe hole.
Yep, its a good old tractor. I have a pretty good idea of how it all goes together now after reading the operator/repair manuals a few times. There are some differences among them though which make it hard to nail down and exact repair manual so its a lot of by feel.
Right, couldn't help myself to wait for the weekend so pulled that RH side inspection hatch and there is was staring me right in the face. Split the shear tube between the differential and the gearbox so must have been digging a bit too hard. Easy fix to pull off the 3PL lift arms top cover, yoink out the pin, pull the shaft out, replace the shear tube and stuff it all back in. Solved my own problem in the end but thanks for those who replied. Its good to have these sorts of places to discuss
Not sure on a 50A but if you have the 3pt. draft and position controls with draft response control make sure to take that cover off and remove the pin for the 3 pt. linkage before you lift the cover. Otherwise you'll bend the linkage and the pin will fall in the bottom.
Glad to hear you got it figured out and have a plan to fix her.
Thanks for the tip. Yes, the draft control was the plate I pulled off to get access to the RH side so will remove it again when pulling off the top hatch. Only other thing I know I need to remove before pulling that cover is the lift arm control link that splits at the bottom so will have to fumble around to try and get it off. Hopefully that will be all I need to do before changing out that tube.