Back to basics, did you replace batterys with like quality batterys with amp hour ratings and good brand name? NOTHING REPLACES QUALITY TROJAN BATTERYS "NOTHING" Ill get lots of static for this but?? Battery lead content is what makes a electric vehicle run, less lead less power and range.
No golf cart will pull hills if steep enough or long enough to draw batterys down.
Did you replace the old probably internally corroded 6 guage cables when replacing batterys? Did you FULLY CHARGE BATTERYS BEFORE USING CART FOR THE FIRST TIME after installation? Batterys require a break in period which takes up to 10 charges before coming to full power.
If all above has been done then we can address what may be causing your problems.
I'm not sure this is how we reply to my first question? I might not have stated the problem correctly, when the cart is in motion it obtains a good speed on level ground. Any incline not severe reduces the speed. The cart seems to have only one speed sensor working it does not shift now or up but only one speed. Thanks again
Have you checked the resistors for loose connections or broken resistors? This is common on older carts so check resistor board for bad connections. If all looks good at contacts on speed control, both fixed contacts and swing arm contacts. Often the swing arm has wear or burned enough to loose contact through full swing. If contacts are burned, clean them up with fine emery paper but be sure and clean all dust off afterwards as this can cause arcing between contacts.