7520 4wd transmission problem

Deere7520 · Sep 29, 2012

I have a 1975 7520 and was pulling loads of beans with it today. Nothing major just 450 bu at a time aboud 3 miles down the road. I was pulling in 7th gear low speed just fine rpms would stay just the same going up and down small hills. When hauling empty I started in 6th and shifted on the go to 8th from range I to II (not high and low) and the tractor just died. I couldn't get it to pull it's own weight in 8th gear even on a roll from 6th but with a full load it will go easily from 4th to 7th on a roll. When I got back I checked the trans fluid and it looked a little low but it wasn't quite level and the torque divider and transmission were so hot you couldn't hold your hand on them. Even the axle housing were hot all the way back to the rockshaft piston. What would be causing this. This is a tractor I bought and hadn't really used it for anything yet but had changed the engine oil but not the trans yet. I plan to change the trans oil and filter next. What sould I be looking for next.
Thanks

tim s · Sep 29, 2012

I am not understanding what you are trying to describe, apparently after it stalled it became alright??

Deere7520 · Sep 29, 2012

After it stalled it started back up and I just had to stay in 7th gear. I couldn't get the tractor to pull itself in 8th. Sorry I forgot to describe that part. It just seems to me like the transmission feels tight in 8th gear like the brakes are being held. Any ideas?

tim s · Sep 29, 2012

I gottcha now,,It sounds like the low range pinion was gualding a bit making it feel like it was in 2 gears at once,, then broke loose,,I have seen this happen before and end up being okay,,but still make a guy worry....

Deere7520 · Sep 29, 2012

That would also explain the heat if the transmission was working against itself. We were using a 4430 to pull another wagon same size and I made it a point to feel how hot the trans was on it and you could hold your hand on it all day just a little warm. I could have cooked an egg on the torque divider on the 7520. Should I mess around with the high & low range shifter or does that just make more trouble since the cables are old. I had read somewhere that if you don't need to use the high & low just to leave it alone.

tim s · Sep 30, 2012

The high/low on those was not meant for a lot of "casual" shifting, such as on the go shifting, it is not made as sturdy as it should have been. It seems like some thing is trying to bind up, creating heat, it"s tuff to pin-point till it seizes up completely,,and that will not be good. You may try to determine where the heat is starting by running a bit and touching it over,,once it heats up the entire case it"s hard to see a difference...I think I would try running using just one range,(leaving the Hi/ Low in Hi position,,and the dash lever in low only for a bit to make a test,,then in High only for a bit...

Deere7520 · Sep 30, 2012

Thanks for the ideas Tim S. I'm going to change the trans fluid and install a new filter and then try to pinpoint it on monday. I'll let you know what I find.
Thanks

7520 4wd transmission problem

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