AWSpoofwil Posted January 20, 2013 Report Share Posted January 20, 2013 so i figured out im gettin about 20.4 mpg in my l20b 78 620 KC, and thats decent, but i hear people getting 25ish.. anyway i can boost the ratings up without loosing too much power? i know its usually one or the other, just thought i'd ask! Quote Link to comment
ggzilla Posted January 20, 2013 Report Share Posted January 20, 2013 Better fuel economy with no loss of power = 5-speed Quote Link to comment
AWSpoofwil Posted January 20, 2013 Author Report Share Posted January 20, 2013 Okay. I had a 5spd in there before but when you put it into 5th it wouldn't stay there so I got a 4speed that I was told it was a 5speed for 180 bux lol. Anything else tho? Like with the carb or anything? Quote Link to comment
Aibast Posted January 20, 2013 Report Share Posted January 20, 2013 do a proper stage 0 on the engine. Quote Link to comment
wayno Posted January 20, 2013 Report Share Posted January 20, 2013 If you can drive 55mph, you will likely get about the best your going to get. Quote Link to comment
Laecaon Posted January 20, 2013 Report Share Posted January 20, 2013 do a proper stage 0 on the engine. only a volvo guy would say it that way. lol. You could try leaning out your idle mixture a hair. As long as you dont make it diesel or ping it could help. Quote Link to comment
Aibast Posted January 20, 2013 Report Share Posted January 20, 2013 I'm a volvo guy, but a proper lookover can improve things a lot. Then when thats done take it to a carb adjustment, and take it to someone who knows what they are doing. Quote Link to comment
ggzilla Posted January 20, 2013 Report Share Posted January 20, 2013 A tune-up (adjustment of carburetor and timing) and proper inflation of tires will bring it up to where it should be. A 5-speed will save up to 20% fuel. Quote Link to comment
AWSpoofwil Posted January 20, 2013 Author Report Share Posted January 20, 2013 Okay all good to know, thank you all! I'll try to fix my 5 speed some time soon... Quote Link to comment
converted_to_datsun Posted January 20, 2013 Report Share Posted January 20, 2013 You live in Oregon, there are Datsuns every where. It's be way cheaper to find another 5 speed than pay to fix one. I think mine ended up being 150 after all the fee's and crap from pick and pull. Also how accurate is your speedometer? Cause it that's not accurate fuel mileage might not be either Quote Link to comment
AWSpoofwil Posted January 20, 2013 Author Report Share Posted January 20, 2013 well the speedometer dont work, but the odometer does work. and i just dont wanna get screwed again on a tranny because with my 5 speed it will go thru all the gears when im playin with it, but when it was in the truck and i tried to put it in 5th it didnt stay in.. Quote Link to comment
converted_to_datsun Posted January 20, 2013 Report Share Posted January 20, 2013 usually if you go to a pick and pull they warranty it for a month or so. And if you pay more they'll do an extended warranty which is like 2 years or something. Or I guess you could take the 5 speed apart and try to fix it yourself. Quote Link to comment
AWSpoofwil Posted January 20, 2013 Author Report Share Posted January 20, 2013 i wanted to try to fix it myself.. with the help of some more knowledable relatives and friends lol Quote Link to comment
converted_to_datsun Posted January 20, 2013 Report Share Posted January 20, 2013 If you do you should make a thread and post pics. I'm sure allot of us would like to see what exactly is involved in fixing some tranny problems Quote Link to comment
AWSpoofwil Posted January 20, 2013 Author Report Share Posted January 20, 2013 okay can do! Quote Link to comment
datzenmike Posted January 20, 2013 Report Share Posted January 20, 2013 If the tranny is out you can remove the tailstock and tighten the mainshaft nut. This was a common problem with the early 71-B 5 speeds. The nut would back off and they would begin jumping out of 5th. Later they had a nut with a flange you could stake so it wouldn' back off. If it's loose this is likely the cause. Never hurts to take a look. Quote Link to comment
converted_to_datsun Posted January 20, 2013 Report Share Posted January 20, 2013 I've heard of people tac welding the nut after tightening so it doesn't back off again. Is that a good or a bad idea mike? Quote Link to comment
Jon B Posted January 20, 2013 Report Share Posted January 20, 2013 If you switch to a 5-speed, what else is necessary? Does you still use your old 4 speed axle? My truck has a 5-speed already, but one of my CV joints took a crap. I don't know if I need to look for a certain axle or not. Quote Link to comment
converted_to_datsun Posted January 20, 2013 Report Share Posted January 20, 2013 I've also heard from a few people that the stock carb is the best mileage you're gonna get with your motor too but I've also heard of great mileage with other carbs. I have an L20b with a 5 speed and 4.11 gears with the stock carb I get about 28mpg, that's combined In Town and freeway but probably mostly freeway Quote Link to comment
datzenmike Posted January 20, 2013 Report Share Posted January 20, 2013 I've heard of people tac welding the nut after tightening so it doesn't back off again. Is that a good or a bad idea mike? Sure. Just a tac, no more. If you switch to a 5-speed, what else is necessary? Does you still use your old 4 speed axle? My truck has a 5-speed already, but one of my CV joints took a crap. I don't know if I need to look for a certain axle or not. The 5 speeds a basically a 4 speed with an added over drive. Usually 12%-15% range for the trucks. If you get the proper one you won't know the difference until you find 5th. Ask Sealik http://community.ratsun.net/user/2344-sealik/ I think you may be able to rebuild them, I don't think you can buy them any more. See what he says. I've also heard from a few people that the stock carb is the best mileage you're gonna get with your motor too but I've also heard of great mileage with other carbs. I have an L20b with a 5 speed and 4.11 gears with the stock carb I get about 28mpg, that's combined In Town and freeway but probably mostly freeway Stock good working carb is good for mileage. 4:11s were used on the '79 620 but with a special wide ratio 4 and 5 speed to match it. Hell the '80 720 used a 3.889 diff. Quote Link to comment
converted_to_datsun Posted January 21, 2013 Report Share Posted January 21, 2013 Hmm my rear end and 5 speed are from an 80... Didn't check the gears was told that year had 4.11. I guess I'll have to confirm that now Quote Link to comment
datzenmike Posted January 21, 2013 Report Share Posted January 21, 2013 Some '80 720s did indeed have 4.11s in them. The King Cabs did but only if equipped with a 5 speed. The Cab/Chassis also did. Quote Link to comment
converted_to_datsun Posted January 21, 2013 Report Share Posted January 21, 2013 Ok then a 4.11 is probably what I have since I pulled them from a king cab. I'll confirm anyway. I took a pic of the data plate In The truck I pulled it from but it didn't say. Quote Link to comment
datzenmike Posted January 21, 2013 Report Share Posted January 21, 2013 It should. Down in the lower right side. HF41 forty-one for 4.11 Quote Link to comment
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