It would be good to post what numbers you have anyways. A hydrostatic transmission will have a fill, they aren't always easy to get at. Also look at the bracketry for the transaxle to ensure that things are secure and that as you attempt to reverse, that it doesn't tilt and loosen the belt. Bear in mind to that reverse problems can appear before forward issues are apparent due to worn belts , debris that keeps the clutch from fully retracting etc.

Thank you tomplum. I am assuming a hydrostatic trans. uses trans. fluid ? There are different types of fluid ??

The numbers I have from the tractor itself -

Model #169003

Serial #2511

Mfg. I.D. #RK20H46A

One of my inquiries said the Model # had been updated to #917169003 ??

Using the above #'s I find nothing on the webb. Even eParts services say no such model exists ??

Randy to answer your question synthetic 5w-50 is what is recommended for K46 and K57 tuff torq , Dana or hydro transmissions , majority of lawn tractors came with 30 weight oil that was much to light causing overheating and loss o r reduction of ground speed . 20w-50 was initially recommended as a substitute . The draining of the unit is tedious and the cooling fan must be removed to access the fill plug quite often . Many lawn tractors have been scrapped when all that was needed was a oil change however as Tom has advised other drive components can cause a loss of drive or erratic performance lol.

https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/ayp/tractors/rk20h46a-1999

The 917 is a Sears manufacturer code. Indicates that it is a AYP/ Husqvarna. I don't think the 917+ your model number pans out in this case. Double check my first post and check those torque brackets. Look for debris above the steering support bracket that keeps the clutch from retracting. The fill should you need to go that way is under the fuel tank. So the rear body easily comes off, then the tank so you have access to the t/a. There should also be a tag on the t/a itself or even sometimes below the seat. It can be topped off w/ motor oil. Likely came w/ 10W30. Some upgrade to a 15w50 for better performance. It could be a Dana or a Hydrogear.

Hello Tomplum thought you had left the forum . Hope all is good for you and yours during this pandemic !

Still here waiting until the great advice runs out then to thank everyone. Not being a regular here I never noticed the "say thank you" notice at the bottom of the posts so THANK YOU :)

tom plum, thank you for the advice. I have to get to work on this problem today as the leaves are not waiting !! To make matters worse, I just installed a new Briggs engine on the vacuum last week. Noticed yesterday that it is throwing a lot of oil out the bottom of the filler tube. What fun is life :)