400 vs 2004r power loss

[Mike T]

Thinking of a mild built 400 to replace my 2004r. Since my new build I've smoked second gear in two different transmissions in a very short time. I like how the 200 drives but the cost to build one seems to make the 400 the best choice for me. Years ago I had a 68 Camaro with a built 327 and a powerglide that ran great. I sold the car to a guy that changed the powerglide out for a 400 and the car was an instant dog and this has always stuck in my mind. Has anyone noticed any power loss when changing from a 200 to 400 ?

 

[Nick Micale]

.................I sold the car to a guy that changed the powerglide out for a 400 and the car was an instant dog and this has always stuck in my mind. Has anyone noticed any power loss when changing from a 200 to 400 ?

Did you ever consider the PG 1st gear ratio vs. the TH 400 1st gear? The 2 speed PG should have had a much lower first gear than the TH 400?

We have done many TH 400 replacements in a GN and found no power loss, but the 400 has a higher 1st gear and with a higher power GN this has actually been a benefit both off the line, and accelerating through the gears.

Other factors will play in the mix such as the turbo size and converter stall. Remember one important thing about our cars, COMBINATION of the proper and correct parts is extremely crucial to efficiently achieve a given performance goal.

 

[Mike T]

I never considered gear ratio. I was more hung up on rotational mass and converters in that swap. The glide had a 3800 B&M 8" & the 400 had a 10" 3200. That is good news on the 400, upsetting my current combo was what I was concerned about because it seems to be on the edge of working very good for me. BTW the current combo should not run as well as it does I have a 3000 Hughes LU, GTQ 70 85 housing and small MT 235's. The car does not launch hard but within just a few feet it pulls like a train and leaves two clean white strips on the road through the gears just on the verge of breaking traction. I think a 3400 converter and the 400 would put it about where it needs to be ? Does that sound about right?

 

[Nick Micale]

I never considered gear ratio. I was more hung up on rotational mass and converters in that swap. The glide had a 3800 B&M 8" & the 400 had a 10" 3200................................... I think a 3400 converter and the 400 would put it about where it needs to be ? Does that sound about right?

There is a big difference in an 8" vs. 10" converter especially in flash stall!

My opinion with a converter for the TH 400 and your GTQ 70 turbo is that depending on your use, a 3800 stall 10" would be good for the street, or a 4000 stall 9" for track use.

 

[Mike T]

Nick, thank you for the good information. My 109 should be capable of about 550 rwhp and to keep with a budget I would like to use as many of the original hard parts as possible from one of the 400's that I already have. I pulled one from a 66 Catalina (has a long tail shaft) and another from a big early 80's RV that was behind a 454 (wrong bolt pattern). Would one be better than the other as far as internal parts or gear ratio?

 

[Eticket]

Have you considered trying a different trans builder? and a non-lockup converter?

 

[Mike T]

Have you considered trying a different trans builder? and a non-lockup converter?

I did not have either of the two built. The first unit was a built 200 purchased from a club member that had pulled it from his 10.50 car. It shifted hard and on time for about the first 500 miles on my new motor. After the motor was run in for a bit I started making a few full throttle runs and on one of the runs the 1-2 shift was really hard and it would not engage 2nd after that (I think it broke the band pin). So for the time being I reinstalled the original one back in the car that had always worked well with my other combos but within 2 months and only a hand full of hard runs the same thing happened.

If I were to go with another 200 I would choose the Extreme 200 but in the future I'm going to build a s2 motor and thought it would be wise to start down the 400 path now.

 

[Eticket]

yep.. probably a good call, but if you're in the mid 10 or higher range, a 2004r and good converter can be had

 

[blackgn1]

After I destroyed several 200's I made the change. I'm never going back down the 200 road with my car. Wife's maybe but I doubt it. While you can see all these threads in this section out about a refreshen up, broke, or just some issues with the 200 I'm out slamming gears and smiling. When I pull second gear(reverse manual valve body) the car is an animal. I love it!!!