DUMB to switch from an M21 to a TH400???

[malicad]

Ok...just throwing this out there. My new "baby", a BBC powered 79 Malibu 2-door weighing 3200 pounds without me with a dyno proven 540 hp at the crank. Has an M21 4 speed trans (not sure if close ratio, but I doubt it) 3.89:1 gears in the Ford 9-inch rear. Hypothetically, how much slower 1/4 mile et and mph would it be to replace the M21 with a TH400 with a mild (2800 or so) stall AND replace the 3.89's with 3.25's? I want a little more "drivability", and it's just too rediculous around town with this manual trans. My brother says go with the TH400, as he's happy with his behind his BBC in his 70 Chevelle. He guesstimates my car running around mid 11's with drag radials. Seriously, that's fine with me. If I lose 4 or 5 tenths by switching to an automatic, Am I nuts? I always thought owning a 4-speed with a big block would be FUN, but, man...it's also scary! I can barely get on it, and Woooooosh....sideways! :shock: :shock:

 

[bowtie81]

Go with the TH400 regardless, you may find with a properly built auto it may be faster.

 

[LS6 Tommy]

An M21 is close ratio. M20's were wide ratio. Anyway, if you're darag racing, the auto will be MUCH more consistent. If you're not, the stick will be more fun. To me, it's a matter of application. I love manual transmission cars & it'll probably never see any racing. Doubtful it'll be on a drag strip. Maybe a road course, but most likely just track days.

Tommy

 

[racecar77]

I did exactly the opposite with my 70 El Camino. Took out the TH400 and put in the M-21. It's way more fun to drive but I don't race this one. Your Malibu will probably ET faster with the automatic unless you are Herb McCandless (retired Pro Stock driver that was known as Mr. Four speed). He was one shifting ****.

 

[abigda]

I thought getting sideways ways the whole point of A big block/4 speed g-body? Lol

 

[Doober]

If the plan is to race it regularly, I'd say 400. If you plan on driving it on the street more and love the feel of shifting a manual like many of us, I'd stick with the 4-speed and not worry as much about ET.

 

[malicad]

I do love shifting on my own, but since every car I've owned since 1998 was/is a manual trans, I thought it'd be nice to just put it in drive and go :lol: ...Yeah, the car will be mostly street, with occasional trips to good old Great Lakes Dragaway. I'm trying NOT to compare the M21 to my daily driver 04 SRT-4, but that's a hydraulic clutch with smooth-as-butter pedal feel. My Malibu's clutch is sensitive, grabby, and when I took my 80 year old father for a ride in my "new car", I seriously nearly knocked him out of his seat trying to take off smoothly. It's a Centerforce dual-friction clutch. Are those supposed to be so grabby? Maybe it's not adjusted right, if they can be adjusted at all (I'm noobie extradorinarre' at manuals of this era)...But, HELL, if the car's seriously gonna be quicker with the 400, I think I'm in for a trans swap over the winter...remember, I also would like to switch the 3.89's to 3.25's. With 540 hp, I don't think it'll be slower at all on the street...thanks guys!

 

[abigda]

If your concerned about the clutch butild a hydraulic like Tommy and I have. Mine feels like I'm working a clutch on a modern car, works great

 

[Robert1320]

If your looking to be quicker at the track good for the automatic.

 

[gman415]

If your concerned about the clutch butild a hydraulic like Tommy and I have. Mine feels like I'm working a clutch on a modern car, works great

What parts did you use? s10? Camaro?