On my 79 f-150 I have trouble with the gas mileage I was wondering if anybody knows if a 5spd tranny out of 87-91 ford would line up with my 351 modified big block. would I have to change the clutch and transfer case is this going to help my mileage.

 

this is just a guess, but I think the 400 went until 81 or 82, and if they had a 5 speed then for a different engine you might be able to take a 5 speed transmission and bolt it to your bellhousing. They would most likely have the same bolt pattern for transmission to bellhousing but a different one for the engine to bellhousing, that's how I'm eventually going to convert my FE powered truck to a 5 speed because the Tremec has the same transmission to bellhousing bolt pattern as the toploader so I'll get a toploader bellhousing and put the tremec on it.

 

Bus with 370 is the same bellhousing.

 

Clint, Changing your rear gear might be a cheaper route to take.

John
jowilker
Club FTE since 01 01


66 F100s
In the still cool hours of the night,
you can hear chevys rusting away.

 

yeah, I agree with John, it'll be a lot easier too probably, less down time and less likely to need some odd part after the parts store closed

 

Heres something you might check out. I have a 79 F150 w/ Overdrive Manual tranny. It's a 3sp w/ an Overdrive 4th. In 78 these trannies showed up in the trucks. My truck has a 302 but I almost bought one that had a 400 and the same tranny in it so I know they can be had for the 351m/400's... whether they will interface w/ a transfer case I don't know.... I've never seen one on a 4wd. My understanding of Fords late model 5sps is that they are made by Mazda... the lighter (smallblock) trucks anyway. And the Mazda 5sps don't have a good rep.... ask around on the newer truck forum. More costly is getting a Tremec 3550. I asked a specialty place around here about options for my 390 (I know its not the same as a 351m) and was told that I could get a 3550 for it or make my 3sp+OD work on it. The 3550 is a beefed up T5 for more torque. The T5 has been used in all kinds of things from Mustangs and Camaros... Chevy and Mopar trucks... the point has been made here many times that it would take a hell of alot of miles to recover your expense.... but haveing lower 1st and less gap between gears as well as the noise reduction of going into OD on hiway is worth something to me as well as haveing a greater range on a tank of gas. How bout getting a modern truck that has a beat body but decent drivetrain and going the MPFI+OD tranny route? useing say a 351W (5.8L) as a donor to swap into yours?