Does anyone know what number should be on an original 1970 442 housing with a posi? and does anyone know how well 3.90 rear end gears would work?
Any help would be great

 

I know the 3:90,s will be alot of fun on the street but on the highway rev kinda high without overdrive.

 

I've got a 1970 442 4 speed car and it came from the factory with 3.23's A previous owner put in a Chebby 12 bolt with 4.10's and I agree with olds425, fun around town but without an overdrive freeway cruising isn't as much fun. I've always thought 3.42's are a good all around gear, fun to drive but not too bad on the highway. John

 

The standard ratio for the 442 was 3.23 and limited slip was an option. I have a picture of the codes that should be on the tube to decipher it.

Here ya go.

OldsreadendIDcodes.jpg

 

I agree with olds425. I have 3:91's in my car and it's not fun on the highway, but around town it's great.

 

Well that depends. Even presuming a non-W30. Depends on trans and AC or not.


M14 3.08, w/AC 3.08

M21 3.42, w/AC 3.23

M40 3.23, w/AC 3.23

 

John, Canadian built 442's came with Chebby 12 bolt's. Not sure why, but it might be the same reason as Canadian Pontiacs used Chebby engines. My 442 has the 3:42 limited slip and a W27 repro cover.

 

TH400 with no air and no w-30

 

Ken I didn't know that. But mines a Fremont build and I talked with the second owner who swapped the rear ends. I'm the fourth owner, the first had it 6 months then went to Viet Nam and sold the car to the second owner. He had it the longest and I've talked with both those owners. Mine was suppose to have been from the factory an M21 with a 3.23 so maybe it was ordered that way? By the time I got it the muncie had been swapped out for a super T10 and the chebby 12 bolt was under it.

1970_442, with an automatic and healthy 455 you should be fine with anything from the 3.08 to the 3.91 I drove a car with a mildly built 455 and TH400 with 2.56 gears for years. It wasn't quick off the line, but once you got it rolling it was OK and the 40 to 80 mph acceleration was snappy. So personal preference, how are you going to use the car and what do you want it to do. John

 

Could be. With the M21, non-air was 3.42 std and 3.23s optional. With AC, just the opposite, 3.23s std. and 3.42s optional.

2.23s were standard, optional were 2.56, 2.78, 3.08, and 3.42.

Also note that with certain conditions, 4.33, 4.66, and 5.00 gear were available via dealer installation.

 

how would a 3.23 ratio be. i plan on putting in a mild cam, headers, and holley carb. will i still be able to spin the rears easy? trans will be a th400. no a/c

 

I you have a good running 455 it won't matter what the gears are. You'll be able to light up the tires at will.