frank5079

I really love how different my truck drives with the 351 under the hood. My only quibble now is that when I had the 300, I swapped out the rear end from a 3.08 to a 3.55 which really made a big difference on take off. But now that I have the 351, it seems a lot easier to take off in second gear because first feels like a granny low gear. I'm toying with swapping my rear diff with an LSD anyway so should I go back to a 3.08??? What do you guys think???

BLDTruth

Hell man, I have 4.10 gears in mine and there is no way I would ever go back. Only a 302, but still a manual tranny. Unless you are looking for good highway mpg, in which case I would say I could entertain the idea.

I am assuming you still have the M5OD, and did not put the beefier ZF5 behind your 351. In that case, the first gear really is a granny, and you can just skip it for daily driving.

frank5079

Yeah, it's the M5OD and I think I might go back to an LSD 3.08

mustanglvr66

Pictures?

frank5079

https://www.f150forum.com/f10/showin...7/#post5914124

Steve83

I have a granny 1st, so I need the higher (3.08) gears to get up to highway speed (which for me means 3 digits).

frank5079

I would hit triple digits too but that pesky speed limiter gets me at 95...

Eric Fullerton

I'm mulling that over myself. Mine is a 4.9 M5OD 3;55, with some engine mods, and 1st gear is over in 10 ft or 10 seconds whichever should occur first. Depending on load and grade it does seem useful sometimes, & with my 18' all steel trailer behind, it is nearly perfect. You can actually wind first out, and the other 4 seem just right. I can pull it with a car on top, over hill and dale and mostly stay in 5th. That however, is a small percentage of how I use the truck. I'm thinking maybe a 3:27, since you are changing it all anyhow, no real need to stay with the factory choices. That would retain some of the trailer pulling ability, and drop it a few revs at highway speed. That is the other problem with the 3:55, it always seems like you should have one more up shift when cruising empty or lightly loaded.

Steve83

I've never encountered a software limit on RPMs or speed in a Ford smallblock truck. But with a stickshift, just disconnect the Gy/Bk (VSS) wire from the EEC since it's not needed anyway (only for electronic slushboxes). If you do it this way, you can put it back whenever you feel the need, but I ran for years without it.


(phone app link)

frank5079

Hmmmmm...on my way home from work yesterday, I was going down the interstate cruising along with the rest of traffic at 90 and was coming up on a big rig so I decided to pass him up on the fast lane and actually got up to the 100 mark. When my truck had the 300 six, it would get to 95 and then fall flat on its face.....as you sped up to 95, it would feel as though you lifted up on the gas and it would slow down....