what rpm at 70mph

[666]

I have a 302 with 3 speed manual and 35x12.50x15 also have 411 gears, what will i be looking at on rpms at 65&70 mph??? also would i get better mpg's with 3 speed auto or manual Thanks

 

[broncodriver99]

http://www.ringpinion.com/Calc_RPM.aspx

Manual would give you slightly better MPG's. Only by a little.

Also, 3rd gear is 1:1 in case you weren't sure.

 

[Explorer]

Assuming 3.50 gears, 2300rpm at 65, 2495 at 70mph. Generally better mileage with manual transmission due to power consumed by the automatic.
For future ref. here's another good site: http://www.grimmjeeper.com/gears.html

 

[666]

thanks, Im just deciding if i want to get a aod transmission or not. I had a 88 bronco with 36x14.50 with a c4 and it wasnt too bad just didnt know if the 3 speed manual was any worse

 

[broncodriver99]

The AOD has an overdrive of 0.67:1. That would bring you RPM's down substantially on the highway and offer better fuel economy as well.

 

[ochretoe]

35" tires and 4.11 gears at 70 mph you should be turning 2762 rpm's. 65 mph will have you at 2565 rpm's or so.

 

[broncodriver99]

I had a 88 bronco with 36x14.50 with a c4 and it wasnt too bad just didnt know if the 3 speed manual was any worse

An '88 Bronco should have had an AOD in it unless someone changed the drivetrain.

 

[broncnaz]

While RPM's would be down I doubt that you would be happy with the OD tranny and your current gearing/tire combo would lose more than you'll gain. More than likely it wouldnt stay in OD and even then it would suck more gas as the engine trys to keep RPM's. You would need about 4.88's or lower to run that AOD effectively.

 

[666]

that bronco did have a c4 put in, So i guess ill run the 3 speed manual , all i want is 13-14 mpgs

 

[NYLES]

that bronco did have a c4 put in, So i guess ill run the 3 speed manual , all i want is 13-14 mpgs

mine gets bout 6-8!

 

[666]

thats awful,man i hope i get better than that

 

[broncnaz]

Make sure the engine is properly tuned and jetted thats about all you can do. you should be able to eek out 13. but those big tires and lift required to clear them suck the mileage right down fast.
Some engine mods inline with your driving needs would help as well like a cam matched for your setup, a free flowing exhaust and good advance curve in the dist will all help up the miles and power.

 

[orangecrush4u]

I have 35/12.5 three on the tree and get 15 to 16 at around 60mph

 

[fordtrucksrule]

i turn 1900 at 70 on the highway. thats with a zf 5 speed and 4.11 and 351w

 

[666]

orange_ are you running carbed 302?

 

[Baja71]

While RPM's would be down I doubt that you would be happy with the OD tranny and your current gearing/tire combo would lose more than you'll gain. More than likely it wouldnt stay in OD and even then it would suck more gas as the engine trys to keep RPM's. You would need about 4.88's or lower to run that AOD effectively.

I agree, or go down to 33s.