Small Engines (Lawn Mowers, etc.): Hydrostatic Trans. Lurches, marvel mystery oil, joe thanks

Question
In the past few weeks the hydrostatic transmission on my late '80s Simplicity 4212 tractor has begun to lurch / buck violently whenever it is in a partial forward or reverse position. The only way to take off anywhere near smoothly is to reduce the engine rpm to an idle, slowly go from neutral to full forward or reverse, then increase engine rpm. The engine runs fine; it is definitely a transaxle concern. The belt is good and properly tensioned; it is full of fluid; the linkage seems OK. Any help is appreciated.

Answer
Hello Joe:

If this is the Serviceable Hydro, then Add 1/2 Pint of Marvel Mystery Oil to the Hydro. From your Description, it Sounds like the The Control Valve Inside the Hydro is Sticking. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.

Good Luck

Respectfully

John

Hello Again Joe:

Thanks for the Update and the Information. However, the Dealer is Going to Tell you Not to Change the Oil and Ect. I have Useed and Still Use Marvel Mystery Oil Because it is Compatiable with All the Hydro Oils Used in Lawn Equipment. They Do Not Want you to do the Repairs at Home. My Business has Been Called a Mom and Pop Operation and Other Names Because I Tell People How to Make Repairs and Even Answer Questions Over the Phone for People Locally. I Beleive if I can Help Someone Even a Regular Custome to Save a Few $ then I have Performed a Service as Valiable as the Repair Shop Does. I Understand the Reason Behind a Lot of Myths About Hydro Transaxles and Until I became Certified in Hydraulics I was much like you. It is Really Unusal for the Transaxle Bolts to Loosen, but I am Adding this to My List of Possible Causes for the Hydro to Jump when Engaged. I have had Only 1 Such Case of the Transaxle Mounting Bolts Loosening since I Started Repairing Lawn Equipment and All My Equipment is Used for 8 hrs a Day 5 1/2 Days a Week. Sorry for Being Wrong, but I wanted you to have the Correct Information about Hydros. By the Way, Most Hydros are Self Venting to Prevent Air Lock. I am Certified by the Government for ALL Hydraulic Systems Up to 10,000psi and have Rebuilt Well Over 100 Hydro Transaxles for Lawn Equipment. Till Next Time. May All Your Mechanical Problems be SMALL ONES and May the All Mighty Bless You and Yours. Thanks Again.

Best Wishes and Good Luck

Respectfully

John

PS Can you Tell me Where this Unit was Purchased, Please. Thanks.

Respectfully

John