Well in a few weeks I am going to be pulling my motor for a rebuild, and Im getting a manual 3 speed w/ overdrive tranny to replace the C6, because I need something with overdrive for the highway. 2600 rpms (with a 4.9) @ 65 kills the gas gauge, it just seems to drop .

I am curious how the motor will act in overdrive with a 3.08 rear end, I dont want to put in the new tranny just to have my engine not have enough power to keep the truck moving on the highway in overdrive. Anyone think I'll be fine with that set up on the highway?

Also what rpms should I expect at 65? Any mild guesses will do fine.

 

I'm running an 86 F150 with the 4.9 and the stock 4sp OD stick. With 235/75/15s I run about 2000 on the highway at about 70-75 mph. The engine really seems to like it there. I'm in need of a good tuneup, probably a carb overhaul and a few other things and get about 17mpg.

 

Sounds good AFSOC, what is your rear axle gear ratio?

 

Go here and put in your numbers. If you have tall tires, you are going to be in OD at 55+ only.

http://www.novak-adapt.com/knowledge/gearing.htm

 

Great link 85e150! I discovered that my top speed will be 129 mph (scary to imagine that brick going 129mph), and my rpms at 70 will be just under 2,000 rpms. It's great news

 

Sorry about that. I've got the 3.08 gear.