400 vs 475 ??

[redgrizz]

Just completed a 4 year build on our 85. It has a 454 bored out .030 and all the extras. First couple trips to local shows, i noticed the th400 seams to slide through 2nd. 1st grabs hard and so does 3rd. Any ideas? I'm not a trans guy. But if its rebuild time, i do have a 475 as an option. Thoughts on which why to go? The truck rolls on 39's with stock 4:10 gears. Could this be a simple modulator valve failing? Thanks in advance.

 

[marks86]

replace the modulator valve on the side of the trans it costs like 12 bucks you can adjust it by a tiny screw inside it also