TH 400 1st gear?

[Dano]

Been "advised" much concerning correct 1st gear needs for my 3500 lb car with 5.14 gears and 30" tire, behind a decent BB chev Stocker and TH 400 trans. Any "rule of thumb" I should be using?

[Jim Kaekel]

Originally Posted by Dano

Been "advised" much concerning correct 1st gear needs for my 3500 lb car with 5.14 gears and 30" tire, behind a decent BB chev Stocker and TH 400 trans. Any "rule of thumb" I should be using?

You didn't say if it's a Stocker, S/S or bracket car but the stock 2.48 is a good starting point. Keep in mind that we're racing at least 1/8 or 1/4 mile and not just to the 60'. A close ratio trans may result in a slower 60' time but due to less RPM drop on gear changes, could result in a quicker E.T. On the other hand a trans with a wide ratio, say a 2.75 for example may provide a quicker 60' but may fall down too much on the gear change. Converter stall also comes into this discussion as well.

[Glenn Briglio]

Originally Posted by Jim Kaekel

You didn't say if it's a Stocker, S/S or bracket car but the stock 2.48 is a good starting point. Keep in mind that we're racing at least 1/8 or 1/4 mile and not just to the 60'. A close ratio trans may result in a slower 60' time but due to less RPM drop on gear changes, could result in a quicker E.T. On the other hand a trans with a wide ratio, say a 2.75 for example may provide a quicker 60' but may fall down too much on the gear change. Converter stall also comes into this discussion as well.

Says BB chev stocker

[Dano]

Originally Posted by Jim Kaekel

You didn't say if it's a Stocker, S/S or bracket car but the stock 2.48 is a good starting point. Keep in mind that we're racing at least 1/8 or 1/4 mile and not just to the 60'. A close ratio trans may result in a slower 60' time but due to less RPM drop on gear changes, could result in a quicker E.T. On the other hand a trans with a wide ratio, say a 2.75 for example may provide a quicker 60' but may fall down too much on the gear change. Converter stall also comes into this discussion as well.

Have been told about the "fall Down" several times. Converter is a ATI 8" set up pretty loose. Haven't run it yet but anticipating a flash of around 5800-6000 rpm. I wish cost wasn't an issue, but of course it is......making the mistake on the ratio is concerning. Have been looking at the Coan LW 400 with the 2.48....and comparing with same trans with the 2.75. any way to determine existing trans 1st ratio? It's a Kilgore deal, recently freshened locally, but the trans guy said he couldn't tell and Kilgore "couldn't" locate original build paperwork.

[Pedigo Perf]

What class and combo BBC?

[Dano]

Originally Posted by Pedigo Perf

What class and combo BBC?

70 Nova.....B/SA....402", GM 401 Alum Head

[Painter]

Turbo 200 with 2.75 low, swap converter for one for a 200. Put the 400 in a pick up truck where it belongs. The fast big blocks are successfully run in 200s.

[Lee Valentine]

Originally Posted by Dano

70 Nova.....B/SA....402", GM 401 Alum Head

Not for nothing with the combo you're running you better adjust your budget or change combos. The price of a TH-200 is going to be one of your lesser expenses.

[Dean Feiock]

Originally Posted by Dano

Have been told about the "fall Down" several times. Converter is a ATI 8" set up pretty loose. Haven't run it yet but anticipating a flash of around 5800-6000 rpm. I wish cost wasn't an issue, but of course it is......making the mistake on the ratio is concerning. Have been looking at the Coan LW 400 with the 2.48....and comparing with same trans with the 2.75. any way to determine existing trans 1st ratio? It's a Kilgore deal, recently freshened locally, but the trans guy said he couldn't tell and Kilgore "couldn't" locate original build paperwork.

A couple observations about your posts,
1) In your first post, you mention 5:14 rear gear. That's a bunch of rear gear for a car that should hit 125 MPH. You are going to need a really good BBC.
2) You stated that you already have the converter. The converter should be the last thing you buy, built to the finished engine/transmission/rear gear/tire combination.
3) There is a lot more to converters than stall. "K" factor, lock up potential, plus fin and stator design are all factors in the converters performance.
4) If you already have a real Kilgore, you already have an "expensive" transmission.
5) If you are looking at Coan, you are looking at an "expensive" transmission.
6) If your transmission was just open and your transmission guy could not tell what ratio was in it...well to be blunt, you need a better transmission guy.
7) If you have a real Kilgore, he has multiple ratios available.

Disclaimer: These are my opinions and not be confused with facts or snobbishness.

[Dano]

Originally Posted by Dean Feiock

A couple observations about your posts,
1) In your first post, you mention 5:14 rear gear. That's a bunch of rear gear for a car that should hit 125 MPH. You are going to need a really good BBC.
2) You stated that you already have the converter. The converter should be the last thing you buy, built to the finished engine/transmission/rear gear/tire combination.
3) There is a lot more to converters than stall. "K" factor, lock up potential, plus fin and stator design are all factors in the converters performance.
4) If you already have a real Kilgore, you already have an "expensive" transmission.
5) If you are looking at Coan, you are looking at an "expensive" transmission.
6) If your transmission was just open and your transmission guy could not tell what ratio was in it...well to be blunt, you need a better transmission guy.
7) If you have a real Kilgore, he has multiple ratios available.

Disclaimer: These are my opinions and not be confused with facts or snobbishness.

In response if I may....
1) car runs 122 mph with old converter
2) Converter matched to all you've mentioned
3) Above my pay grade right now
4) This I know
5) Coan is on the way (when referring to "expensive" I consider $ 6500.00 and up to be expensive)
6) You are correct
7) Again, you are correct

Disclaimer: When advised to get rid of my Motorhome Transmission, yes I considered that "snobby". Most of the replies I got were considerate/helpful as yours was.