Ok I'm going to purchasing a th400 for my 97' formula real soon. And I have a few questions.

Flexplates.......
Do I want an internally or externally balanced flexplate? Is any one brand better then the other?

Converters......
If I'm going anywhere from a 3500-4500rpm stall what size converter will I need. 9" or 10" converter or neither?

Driveshafts......
Does anyone already sell a off the shelf drive shaft that will fit in a 97' lt1 fbody running a th400?

If I'm going to be running reverse manual valve body, do I need to purchase any special brackets or tv cables? I know the B&M shifter I wan't comes with one.

Thanks for the help guys, I've tried to do my homework on this site, and I still ran into those questions.

Mike

 

I just had a th350 swap done in mine. Flexplate- I think that would depend on what the motor needs for balance rather than the tranny. Converter- Go with what your builder recommends. Some places get 10 inch to stall real high, not sure of the advantages of the converter being 1" smaller if the stall is the same, maybe it carries more heat? Is that a good thing? Not sure. Driveshaft- My builder purchased a kit that allowed a 4L60 tailshaft to be bolted up to the back of my th350. I used my stock driveshaft because the overall length of the tranny is identical. I'd look into seeing if there is such a kit for the th400. Shifter- the stock shifter will work. You MAY have to file a tiny bit on the detents, but they didn't have to on mine. On my console overdrive is 3rd, drive is 2nd and 2nd is 1st. I have forward pattern valve body. If you are running full-manual valve body you will not need any tv cables or anything like that, you will be shifting the tranny yourself. You will need a new dipstick tube though. Lokar makes a flexible one sold just about everywhere.

 

thanks for the info.

Mike

 

I had my converter custom made for my car, ATI made it I gave them all the specs on my car and they set it to what my motor needs, they wanted mine to be a 10 inch and mine should be around 4000 stall speed, the flex plate is an external balance the factory flex plate has a weight on there, unless you had a motor built and had everything internal balanced. I got Spohn to make my drive shaft sence i know what Im going to put to mine sence my 400 has a trans brake in it.

 

Ok I'm going to purchasing a th400 for my 97' formula real soon. And I have a few questions.

Hope you don't hate it as much as I did.

Flexplates.......
Do I want an internally or externally balanced flexplate? Is any one brand better then the other?

Depends on if your motor is internally or externally balanced. If your motor has not been rebuilt, it will need an externally balanced flexplate. IOW, a stock rotating assy. is external balance. Unless it's a super hi-po setup any of the big names should be fine.

Converters......
If I'm going anywhere from a 3500-4500rpm stall what size converter will I need. 9" or 10" converter or neither?

The size will be determined by the desired stall and the amount of power the motor puts out. Talk to whoever will be making your converter. In general, smaller converters stall higher and cost more. Smaller converters also have less rotating mass. But that's a gross generalization.

Driveshafts......
Does anyone already sell a off the shelf drive shaft that will fit in a 97' lt1 fbody running a th400?

You need to measure to be sure you are getting the right length.

If I'm going to be running reverse manual valve body, do I need to purchase any special brackets or tv cables? I know the B&M shifter I wan't comes with one.

A manual valve body tranny doesn't need any connections except the speedo and the shifter.

Thanks for the help guys, I've tried to do my homework on this site, and I still ran into those questions.

Again, you really should think this through. This was the only mod I regretted doing - wrecked the car for anything other than occassional street use, so I went back to a T56.

Rich

 

I have a spohn driveshaft and an ati converter that is a streetmaster 3200 stall for a th400... bought one but looking to go 6 speed. Converter was around 800 and ds like 450? Not sure but both look like new, suppose to have 20 miles on each. If your interested, lmk.

 

Yeah, but be honest.........wasn't it fun as hell driving it?

I love my TH400.
It is a bit annoying to only be able to travel at 60 MPH on the highway but its not like I drive the car all the time.
Other than that I would not change one thing. Its a killer on the street.

 

Stupid question but what does your top speed change to with a th400 or 350 because of the 3 gears? lets say you have 3.73's out back.

 

Top gear in a TH400 or 350 is 1:1. An A4 has a 0.70 4th gear and a 1:1 third gear. So, top gear with the TH400/350 will be like 3rd in a 4L60E. It was no fun for general street driving, IMHO. But if you just want cruise around and drag race, it's fine.

With street tires (26" diam) I was at ~3,500rpm at 75mph with 3.23's. This is a little higher than calculated due to converter slip. Remember that a TH400/350 does not use a lockup converter. With 3.73 and a 26" tire you will see ~3,800rpm at 75mph.

Rich

 

Wow. That's really something to think about.

 

Thats why people put od tranmissions in older cars. Plus with gas prices, no way I'm putting a th400 back in my car.