View Full Version : Anyone have experience with older NPR transmissions?

GreenSouth Landscapes
02-20-2008, 12:49 AM
I am working on a Super Lawn Truck. It is a 1989 Isuzu NPR. The truck runs great and for the deal i got on it, i really couldn't go wrong. The truck drives, shifts and runs great but i cannot get the truck to shift into the high gear and it will not down shift to passing gear when put under heavy load. Anyone have any suggestions. The previous owner told me about an "overdrive switch" but they are not sure and i've never worked on these older trucks before. thanks in advance.

02-20-2008, 12:55 AM
I use to have a 92, burned 5 transmissions, Actually traded it in to chevy for $1500 with a burned one tranny in it truck had 120k

GreenSouth Landscapes
02-20-2008, 01:27 AM
well i know there is a chance that the tranny is the problem and not necessarily a switch but the truck is a great advertising tool and even if i could only use it with my commercial business, which most of them are all on the same main stretch of our city it is worth what i gave for it. I am pretty much on an extremely populated street for 8 hours every wednesday and on another really populated area in a different town for 5 hours on Mondays. The problem i have is that the truck is really only safe to drive at about 45mph which will not work traveling interstate. If i could just get it to shift into the high gear, the truck will probably get 15mpg and do 60-65mph. eh who knows i might just take it to a shop and see what they think.

04-01-2008, 11:24 PM
what did you find out about the npr transmission? I have the same problem with mine.

GreenSouth Landscapes
04-02-2008, 01:00 AM
haven't fixed it yet but there seems to be some type of kick down switch on the transmission to make it drop into the passing gear when you press the accelerater while cruising. We think it is stuck open so it is only using 3 gears not the 4th. Will know something by weekend for sure.

04-02-2008, 02:05 AM
Thanks ... I havent found anyone that knows how to work on these transmissions .. I cant wait to be able to go over 45 again!

04-05-2008, 09:09 PM
The early transmissions were built by JATCO (Japanese Auto Transmission Co.) but yours is probably a Chrysler transmission. The JATCO transmissions would fail about every 35000 miles while the Chrysler gives very little trouble.


04-05-2008, 11:24 PM
Ya, if you find out what is wrong, let me know too. mine does the same thing.

04-07-2008, 01:21 AM
The newer NPR's now have the Aisin Seik 6 speed automatics. Their are several companies online that rebuild these transmissions