LUVTruck.com

HI IM NEW HERE SO BEAR WITH ME MY S15 HAS THE 2.2 ISUZU DIESEL
MY GLOVEBOX STICKER SAY REAR END HAS 3.73S BUT @3800RPM I ONLY RUN 57-58 MPH. SOMETHING JUST DOESNT SEEM RIGHT. TRUCK HAS 198000MILES ON IT STILL RUNS STRONG JUST HAVING DOUBTS ABOUT MPH AND WHAT KIND OF MILEAGE CAN I EXPECT
THANKS,GRITSNGRAVY

Hi and welcome to the site. I have an 82 LUV that is comparable to your S15 in that I have 3.73 rear gears and a 5-speed manual transmission. I do believe 57-58 mph is too slow and I'd expect something in the 60-65 mph range. What size tires are you running and are they the factory size? If not that could be your problem and your speedometer could be reading too slow (when doing 57-58 according to the guage you may really be doing 62-65). Otherwise I'm not sure what else it could be.

Salvy

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1982 Chevy LUV diesel
2.25" stainless exhaust
w/ MagnaFlow performance muffler

The tire size would change his actual road speed, but not his indicated road speed. His speedometer & tach would indicate the same speed and RPM regardless of tire size (or even if the truck has no wheels and it's up on jack stands).

Could the clutch be slipping at that speed? Clutch slippage generally shows up first in the higher gears.

Jack

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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.com
IsuzuPup.com

I have a 1991 S15 with a 3.73 diff, and a transmission out of a gas (geared a bit higher than the diesel tranny), and so mine revs 2500 at 60mph. Tach is accurate, speedo not dead on but close enough. Does you engine sound like 3800? Sounds to me like a slipping clutch.

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Bona Fide diesel fanatic.
1994 Chev S10 Ext Cab Isuzu Diesel 5spd
Kubota B6100 HST diesel