View Full Version : simplicity transmission hydrostatic from 1985 model 7790 Diesel

01-31-2007, 10:12 PM
Hey guys, I have a broken shaft tube on my Simplicity and these rascals are hard to find. I would hate to part her out but that might be the only option. Anyone have any thoughts? She is a simplicity model 7790 witha Lambordini 18 hp diesel. I dont know what model the transmission is although I think it is a sundstrand. I also know it comes in allis chalmers models also.

01-31-2007, 10:55 PM
I'm not sure what you are calling a shaft tube but I went here;


And didn't see any (axle) shaft tube ? in their parts look-up.

Scroll to the bottom of their page for parts look-up to find what you need.

02-03-2007, 03:51 PM
Thanks for looking into it. I found what i think is the part. It is #1673801sm, called the tube assembly, axle.

My tranny also will roll, but it doesn't matter if you pull the release or not. There is a U shaped tab you on top of the tranny you pull up to release it for towing, and push down for engagement.
Either way she rolls.
Do you think there might be other problems????

I know these are expensive tractors, is it worth fixing or should I part it out.

02-03-2007, 07:02 PM
I have an Allis Chalmers mower that was made by Simplicity for them that has the same hydro and rear end. On mine, when you push down on the tab, it releases the hydro so it can be moved without the engine running. You pull it up to allow the hydro to operate. If it has been sitting for several hours or longer you can push it without messing with the tab, but if you have just shut off the engine, you have to push the tab down or you'll just slide the tires on the one I have. Hope this helps.............

02-04-2007, 03:10 PM
Thanks for the info. Do you have any idea what a 7790 diesel would be worth if running and in good shape? It has the hydro drive, a rototiller and new starter. Very good running Lombardini, but the deck is rusty.
Thanks again.

02-04-2007, 05:44 PM
I'm really not sure of a good price for the mower. There was one on eBay that had a Kohler engine on it and the guy was asking 450 for it. I imagine that yours would be worth more with the diesel engine, but to put a price on it, I'd say some where in the 8 to 900 dollar range. That would depend on how it looked, and you say it runs good. It probably is worth more to you, but if a collector came across it, and just had to have it, you might could make both of you happy !!!

I've got an AC 917H, which is the same mower with a 17 Kohler on it. Bought it new in 83 or 84 and paid too much for it according to most people. But I've still got a good hydro mower that cuts good, runs good, and will still run the tiller I got better than most. The people that said I gave too much for it have gone through 8 or 10 of the "cheep" mowers that only cut grass, so in the long run I think I did OK. Like the old saying, you get what you pay for..........

02-04-2007, 10:25 PM
Thanks for your input.
Do you happen to know if the AC 914 is similiar to the 920 model? I found a transmission from a 914 and the 920 is supposedly the same model as my simplicity 7790.
Thanks again

02-05-2007, 06:36 PM
Not sure about the interchange between the two models you mentioned. You might could go back to Jack's Small Engines and use the parts lookup again to see if the part numbers were the same on the transmissions. If they are, then I'd say you could use it with no problem.

diesel king
02-20-2007, 01:36 PM
i would be interested in buying the 7790 diesel you can email me at rgarbers@fulton-net.com

diesel king
03-03-2007, 11:56 PM
i would be interested in buying the 7790 diesel you can email me at rgarbers@fulton-net.com or call me at 419-583-7659 craig that is my cell phone

06-25-2008, 12:53 AM
We love our Simplicity 7790 with Lombardini 18.5hp diesel engine. It is a work horse and solid. Unfortunately the starter just went on it. Any where we could get one as a suggestion?

it states it is a bosch 449 00001214002 12v on it.

Help we don't want to part it out. We have all the parts for it too - snowblower, rotatiller, grass cutter, blade, etc.....

07-19-2008, 09:24 PM
I have a good starter, I replaced the Diesel with a gasburner