Examine the transmission - any wet spots ?
If the unit uses oil there may be a level/fill plug.
Being a cheap mower, grease is probably used...
Probably some linkage needs to be adjusted , wear and tear dictate this and regular service, which can be costly - and not worth it for a mower over a certain number of years old..

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Here is a link that might be useful: original posting

I did check the linkage, all is tight. It is behaving like an old car of mine that developed a sudden transmission fluid leak, doesn't drive regular speed on flat ground.

can't really see any wet spots on it, but being 10 years old it could have just naturally consumed some of the fluid perhaps?

Peerless VST hydrostatics had lots of problems and the trans was superseded. The replacement trans was not cheap.

Perhaps this thread will help you... http://forums2.gardenweb.com/forums/load/tractor/msg1009401210140.html

I'll check that out, but this one says it's a Tecumseh..I think there is a model # on it if that helps?

IIRC Tecumseh either manufactured or acquired Peerless.

Ah so probly is one and the same then..would the part # on the top of the tranny case be helpful?