Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem

rustybear

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
I have a Scott 50567X8 20 HP tractor that was having problems with the 205-023B transaxle. Was cutting some thick grass, when tractor quit moving. I had been having problems with was not being able to go very fast up hill in forward and in reverse. Had just replaced drive belt, so I knew it was okay. After extensive examination, I determined problem was in the transaxle. Removed the transaxle and took it apart and found a roll pin broken. Replaced roll pin, cleaned inside of transaxle. Found no other problems. All gears, shafts, seals, bellows, motor and oil pump, visually looked good. Reassembled. Refilled with Synthetic oil 15W50 motor oil in the Hydro section (about 1.5 qts) and 85W140 Synthetic blend gear oil the the Differential section (8 oz). Tested with back end on jacks. Seemed great, forwards and reverse.

Now for the ground test. Great on level ground, but still low power going up hill forwards and in reverse. After reading others with the same problem I decided to purchase the 799031 kit from Sears direct for $ 543.00. The kit includes the new LTH transaxle, a new longer drive belt, a couple brackets, pulleys, clutch spring, and necessary hardware, and installation instructions. Oil already in transaxle. Installed, tested with back end on stands, worked real good.

Now for the ground test with the new transaxle. Real good on level ground. Fast forward and reverse. Fast in reverse up a hill with about a 22 degree slope, but in forwards up the hill I'm getting something grabbing and releasing. grabbing and releasing in the rear. Can't figure what it is. Belt is not slipping. Rechecked everything per installation instructions, but everything appears to be okay. The tricky item in the installation was the Disconnect Linkage Rod under the seat that engages the transaxle for drive and disengages for manual pushing. It had to be bent to make it work. I had a rough time with that. At one point, I removed the rod, because in drive mode, the disconnect lever on the transaxle is relaxed, not under tension. That did not help.

I have said a lot here, but I hope someone out there has installed one of these 799031 kits and maybe had the same problem and can help me. I am sure it is something simple, but I haven't been able to figure what it is.
 

BlazNT

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
Sounds like you have air in the system. Have you purged the air out of the system?
 

rustybear

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
Sounds like you have air in the system. Have you purged the air out of the system?

I purged with trany disengaged and tractor on jack stands, 8 to 10 seconds in forward and reverse about ten times. Then engaged, forward 8 to 10 seconds, then reverse for 8 to 10 seconds about ten times. Repeated the whole process, disengaged then engaged, all at a slow to moderate engine speed. Then removed jacks and tried outside. Again, on level ground, beautiful. Reverse up, hill, beautiful. Forward up hill, same problem. Something grabs and then releases. This time, I removed the disconnect linkage rod, to be sure the disconnect lever has no pressure on is in the relaxed position (engaged). Same exact results. The two things I wonder about are the Break Return Spring and the Hydro Link. Could either of these cause this problem ? Maybe the spring has lost some of it's tension or maybe something in the hydro linkage needs to be adjusted ? It only happens on an upgrade. On the Jack stands, it worked great. Should I add more oil to Pump and Motor Module? It calls for 1.25 to 2.00 inches of oil when measured from the inside bottom of the module. I had checked it when I received the transaxle, and it measured about 1.75 inches. Could the slope of the hill cause the oil to loose pumping for a second ? I'm grabbing at straws, but if I can back up the hill fast backwards with no problem and go forwards and backwards on level ground with no problems, and work perfect on the jack stands, what is happening in the transaxle, differently, going up a hill in forward?

Any thoughts? Thanks for any help you can give me. This replacement tranny (799031) seems great, very powerful, but something about going uphill in forward, just isn't right.
 

BlazNT

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
Pull yhr tires and wheels off. Check the key to see if it is still square. Take pictures and post them.
 

rustybear

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
I did do that and had replaced the axle keys with new ones..

Just learned today, I am not the only one having this problem. Everything works on level ground and backing up a hill with out any problems. But, going forwards up a hill, you get a clicking sound and pulsing of the tractor. Well Tecumseh/peerless, just happens to have a non advertised repair kit for the LTH 2000 series Hydrostatic trans axle. it is part number 799032. Mind you the transaxle kit to go from a VST to a LTH is part 799031 and repair kit 799032 !!!:tango_face_sad: This kit is a neutral lock out repair kit, part# 799032 and goes in the Differential section, not the pump/motor module. Well I got it from sears, where I got the trans axle from. No warrantee !!!! I had hoped I wouldn't have to pay for the kit, since I just bought the trans axle and immediately had problems. Oh well, it just costs $42.68 and with a discount coupon I got $6.36 off. So with tax and shipping I paid $47.63. If it solves the problem, I will be ecstatic. I will post how it works for me when I get the kit installed.
 

rustybear

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
Hi guys, Here is an update after installing the 799032 repair kit. It didn't work. We were very careful with the replacement, even though we really didn't see anything wrong with the original parts. The only thing disturbing was all the RTV that was used in the "NEW" 799031 tranny from Sears. Way too much. It coated the axles, got into the oil troughs that bring oil to the axles. coated the ends of the bearings. We had to carefully remove the mess. And it got down behind the disconnect collar that allows you to engage and disengage the transmission. But, with all the cleaning and installing the new parts, properly sealing the the differential module, using the alignment kit to reinstall the motor/pump module, refilling with gear oil, we installed it back on the tractor. tested. and got the same results. We thought, just maybe we missed something, so took it apart once again, but we did it right the first time, so put it back together again. installed it back on the tractor, tested, no difference.

As was questioned by Blaznet: Sounds like you have air in the system. Have you purged the air out of the system? I had, as I mentioned in an earlier reply. But it makes me wonder if the problem could be in the motor/pump module. I know now the differential is good. Tractor has plenty of power. goes forward and backwards fast, on level ground, fast backwards up a hill, still grabs and releases going forwards uphill, as if there was air in the system. It is a little better then before, but just not right. I wonder if there is air in the pump module, that just keeps trying to get out in the forward motion up a hill. Sounds crazy, and I don't understand why going backwards up a hill, it works great at slow, medium, or fast speed, but not forwards uphill.

Has anyone else installed the kit and still have the same problem. So tempted to open the module, but don't know what to look for and I don't have a drawing of the inside of the module. I do have drawing of the differential. Any suggestions ??????
 

bertsmobile1

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
Time for left field ideas.
Try blocking the mower or putting a chain on the back to prevent it from moving
Get under and have some one else try to drive it foreward.
You are looking for belt slipping.
Next did you use the correct oil ?
I note you said gear oil and usually they run full synthetic in Hydros.
 

rustybear

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
Thanks for your reply. My first test always is with the back end off the ground on jack stands. going forwards and then reverse. That always goes great, because there is no load. And as I said on level ground, it goes quite fast forwards and backwards, with no problems what-so-ever. It is when I go forward up an incline.

By the way, The Hydro module is Full synthetic 20W50 almost full, as I added oil, thinking maybe going up hill, the pump maybe isn't always getting oil. In the differential I am using Valvoline Synthetic Blend 85W140.

What I am thinking of trying, is to put the rear end on jack stands and the front end on jack stands, but higher then the rear, to simulate going up a hill. The rear wheels will be about an inch off the ground. I will test to see if I have that problem. I will keep you posted. Again, thanks for your input. You made me think of ways of simulating going up a hill using jack stands. Thanks !!!
 

BlazNT

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
While you have it in the air check for a tilting motion of the rearend. It should not move at all either up or down.
 

rustybear

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  • / Scott 50567X8 replasced hydrostatic transaxle with tecumseh 799031 problem
While you have it in the air check for a tilting motion of the rearend. It should not move at all either up or down.

Well. finally we figured out why the so called replacement transmission, (799031) was having problems going uphill forwards, I have tried three 799031 VST to LTH transaxles kits, all with the exact same problem, a grabbing and releasing, grabbing and releasing, when going forwards up a hill. Recently my mechanic came upon a H2000-020 out of a tractor given to him with a blown engine. The transaxle looked almost exactly like the 799031 kit which is a H2000-026. There were a few minor differences. The main difference was in the Hydro unit. The input pulley shaft was shorter. The pulley was too low. I couldn't get belt alignment.
We tried to make it work. but had to give up on that idea. We were certain the problem was in the Hydro module, so we decided to try the new hydro module on the old differential. We observed the hydro module and the differential of the used transaxle fit together very close. The new Hydro module and the old transaxle differential also fit closer together. The new (799031) hydro module and differential did not fit together as close. Anyway, with the old differential and the new hydro module, the fit was a good match. To make a long story short, it worked. I now have a good working tractor. fast forward and backwards and able to go up hill forwards with no difficulty, not real fast on a steep grade, but I can mow going uphill.
I hope this helps someone having the same problem. One thing I didn't try was fitting the old Hydro unit with the new differential. That's another day !!!
Again thanks for all the input. Your suggestions helped me to be persistent in finding a solution.
 
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