engine and tranny question concerning highway speeds

[hutsonnl]

360 engine, 4 speed tranny with granny low, 4.10 gears, and 38 in tires. Maybe I'm just a big dummy and worrying too much but with those numbers my truck did not do well on the highway. anything above 55 the engine sounds like a 12 yr old def indonesian girl being violated. I saw an article in some off road mag where a dude put a modified over drive unit between his engine and tranny (think it was a C6). Any thoughts on this?

 

[blacksnapon]

360 engine, 4 speed tranny with granny low, 4.10 gears, and 38 in tires. Maybe I'm just a big dummy and worrying too much but with those numbers my truck did not do well on the highway. anything above 55 the engine sounds like a 12 yr old def indonesian girl being violated. I saw an article in some off road mag where a dude put a modified over drive unit between his engine and tranny (think it was a C6). Any thoughts on this?

never seen one, so I couldn't tell you. The 360 isnt known for high rpm usage anyway.

 

[Mil1ion]

Please note:

Granny gear IS 1st gear...nothing more.

The term came from little old ladies driving very slow (like In 1st gear).

EVERY transmission has 1st gear or a granny gear.

Please call the the transmission with the super high 1st gear ratio what it is.

 

[Mil1ion]

To raise fuel economy keep the RPM'S down.

But a 360 with 4:11 rear with big tires and the term fuel economy Do NOT go together.

 

[LEB Ben]

With that setup and scenario, you should only be doing about 2000rpm...that isn't screaming too bad. But as stated, it's not a high rev engine and it's not a hybrid...so you'll be lucky if you can get better than 8-10mpgs at highway speeds.

 

[hutsonnl]

so do I need to change my gearing or tranny?

 

[LEB Ben]

so do I need to change my gearing or tranny?

Well...the tranny is bombproof, so I wouldn't change that. As for gearing, it's kinda a double edged sword, the gearing you have now provides some power to the ground...but sucks the gas...with your setup, I feel if you went with a higher gear (numerically lower) you would constantly have your foot on the gas to maintain speed...thus sucking gas. To be honest, you drive a vehicle with the aerodynamics of a brick...good mpg's aren't gonna happen. But back to your question...you should only be rolling at 2000rpm with your set up at 55...that's a good rpm range. Do you have a tach to tell you what rpm you're actually turning. And for the record, most aftermarket OD units for these things are gonna run about $2500. I guess I really don't see the problem.

 

[1985 Ford F-150]

That old 360 is probly strugglin to push them big old meats ya got id go with a 4.56 gear set to get your rpms up a bit and take alot of the load off the motor. My 72 has the same gears, tranny and used to have a 360 in it and I threw a tach in to see what my rpms. That one turns 2700 at 60 and my 76 would do 2500 at 60 with 35s so your probly 2200 or around there. The top speed might go down a bit but itll give ya more low end grunt where ya need it and itll bring your rpms up some and help with gas mileage.

 

[Mil1ion]

Change the tires to LT 235's (31")
and change the diff to a 3.00-3.25 ratio

3.54's are common on 4x4's

 

[blacksnapon]

take the 360 out and replace it with a 390.....twice the horsepower, same fuel mileage......bolt in replacement.