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I recently purchased a 1980 luv with the stock motor. Everytime i am driving in 4th gear and i am up around 60 mph and let off the gas i get the loudest backfire i've ever hear. Any suggestions?

I was also wondering if anyone knows the gear oil specifications for the 4speed tranny in it.

Thanks,
Sean

The backfire could be some carb adjustment problem, but it can also be caused by problems with the smog pump. If the smog pump has been removed, make sure the the AIR manifold is blocked off or if that is gone too the holes in the head where it hooks are closed up. The AIR manifold is right above the exhaust manifold, a long tube with four small tubes hooking into the head right next where the exhaust comes out. If the motor can suck air in through there it can give enough Oxygen to ignite unburnt fuel in the exhaust, causing the bang. Usually it takes a combo of problems though, like running a bit rich to begin with.

The 4Spd trans is supposed to take SAE 30 motor oil, not the 90 weight you might expect. There are stories of people using 90, 30, and everything in between though. Do a search on here for something like "tranny oil" for more info. I go with what the book tells me and put in 30, have yet to have a trans go bad on me in more than 15 years of driving LUVs.

well i would be suspect of the carb and other things. I would just do a general tune up (cap plugs wires rotor cap and points) and then tune up the carb and see if that fixes it. About the tranny oil thing, the shop manual and my owners manual says to use 30wieght. Though if you going to be using your truck as a work truck and towing whith it, it might not be a bad idea to run 50 or 90 (my dad ran 70w90 in it for 20 years and the truck realy had to earn its keep and it has no problems).

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1980 LUV 4x4, going under re-construction...