Hi all, I recently bought a 1963 F100 with a 292 yblock and standard duty 3 speed top loader tranny. I am looking to rebuild it into a safer, reliable version of its self. I am setting up to rebuild the front end, add front discs, and then rebuild drivetrain. My question on the drivetrain which I think is a age old question is what is most cost effective way to get a little more top end out of the 292. New gears? New tranny? Both?

 

What is the gear ratio in the rear end? What size tires are you running? What do you use the truck for?

 

Currently it has 3.89 gears at least according to the warranty number (vin). Tires are 235 x75 x 15. I just use it to cruise around town, carry my mountain bike, maybe go to hardware store to pick up stuff. But no towing or heavy hauling.

I’ve looked into a FE motor and a tremec t5 but that’s a bit expensive for me right now so I’m looking to get the most out of the drivetrain as it is.

 

I went from a 3.5 to 3.0 rear end gears, axle swap, in my '66 with a 240 and 3 on the tree. It's nice at the top end, but a dog starting off on any kind of slope. It also reduced my city mpg as I spend more time in 2nd gear. Changing the gears is the easiest to do. I don't think I would bother unless going to 3.2? or 3.00 gears.
I would think it would be <$1400 to do.

 

Mushroom, you are contradicting yourself, You want "more top end" in your first post, and "just cruise around town" in your second post. I think you need to clarify what you want.

Are you trying to get a higher top speed, or more acceleration at low speed? You can't do both unless you go with a lower gear in the rear,(4:10/4:56) and an overdrive transmission to get your high end back.

 

Hi EricJ,
Ok yea I can see that could be confusing, I am looking to get the truck to be able to go down the road at say 60 mph a little more comfortably. Currently it is wound out pretty high at 50 and at 60 it is screaming. As far as cruising around town - in the area of the country I live cruising around town includes highway driving, its just a necessity given the way the roads are mapped out.

 

Play around with this using your current drivetrain - and mix/match tire heights.

assuming 3rd gear is 1:1 and the 235 tires are 28.9 tall - and using 3.89 - you are over 2900 RPM’s at 65 MPH. 2700 at 60 etc etc.

i have the 4speed with a 3.50 rear and 33 tires. According to this it’s running about 2103 rpm’s for the fastest road around here (55). Doubt I’ll be on the highway with this 4Wd too often.

not sure what the 3rd gear ratio is for a 3 speed.

Engine RPM Calculator

 

3rd for a 3 speed should be 1 to 1. If you are gonna run no more than 60 I wouldn't do anything but that is me. When my 64 with a 292 and the T98 with 4:10 gears was my daily driver some 30 years ago I would get out on the highway and run 70 all day long. Sometimes 75 and 80. It was turning some pretty good RPM's but it stayed together. The final on the T98 is 1 to 1 also so you would be turning less RPM's at 70 than I was. The reason IMHO that it sounds like it is screaming is because of the engine fan. It is a solid mount therefor it is turning all the time unlike an engine with a clutch type or viscous fan, (what I call them) they only turn fast as needed.

 

I'd go with a 3:25 rear and see how it works for you. If it's a little lacking in power maybe do some engine mods in the future.

Eric

 

60 mph in these trucks will be in the area of 3000 rpm. High by modern standards, but fine. Usually, if it is screaming at that rpm, it needs a new or quieter muffler - cheaper and easier than most any driveline change.
Check your exhaust, check your rpm with a tach, don't guess, and use that info to decide.

 

It would be cheaper and much easier to get taller tires. Put an extra leaf or two in the front for clearance, and you're good to go.

Even my 3.08 and 1 to 1 transmission is geared too low for 70 mph with 30x9.50 tires.

The thing in your favor is the low end torque a 292 has. They are like my 300, they run out of breath at higher rpms.