CVS or hydro? if unsure, look in the cavity under the tilting seat - post full model number here.

I'll have to get back with you when I get home to check. Thanks!

Model # 917.274040

HydroGear Transaxle , Model# 314-0510

see http://www.managemylife.com/mmh/lis_pdf/OWNM/L0407070.pdf for a copy of your tractor's manual. Chk the maintenance section for details on motion drive belt condition and motion control linkage adjustment.
If all chks out there, may try replacing worn out hydro fluid - which will prolly require pulling the tranny out and turning it upside down to drain/refill. Chk Hydrogear's website for details on what oil to use.

Thanks! I have the manual and will see what it says.

OK, finally changed the drive belt (definitely worn out) but still no reverse. I have a owners manual for the linkage, but I think i have not correctly described the problem. I can't get the transmission lever into reverse. I can put it into the reverse slot, but it will not push back.

you'll need to pinpoint/repair/replace the part(s) frozen up preventing the hydro control from going into reverse. Hopefully it will be something outside the hydro tranny housing... :)

I checked the linkage adjustment
today, and it checked out OK. The lever still won't go in reverse much. The mower is barely creepIng backwards.

then prob most likely internal to tranny.

might be time to get sears service out to look at unit, them verify external control linkage OK and give you quote on fixing hydro trsnny... so that you can make an informed decision about tractor repair vs. replace with new one......

Would the idler pulley cause any of these symptoms?