Shifting an automatic
Safety Car
Joined: Nov 2006
Posts: 4,449
Likes: 0
Miles
Melting Slicks
Joined: Mar 2004
Posts: 3,470
Likes: 18
From: Lake Ozark, MO
Don't need to pull the tranny - just valve body and governor. Transgo comes with a video with step by step instructions...lots to replace as mentioned above....if not mechanically inclined ..I would skip this mod as a do it your selfer...........
Melting Slicks
Joined: Aug 2005
Posts: 2,821
Likes: 204
From: Lincoln CA
As I mentioned before, there is an overspeed limiter valve in the THM400. When governor pressure exceeds a certain value (it increases proportionally with output speed), the transmission will force a shift...even if the shift lever is still in "L or 1st" position. At that point, I always manually moved the shift lever to "2nd" and then shifted into "3rd" manually at whatever rpm I chose.
Most automatics, unless purposely built not to, will shift themselves at a certain pressure level. Consider it an idiot override. The automatic in my 2000 LS1 Camaro will actually shift itself at a lower RPM if held in gear than if you just leave it in (D) and mash it.BTW, my Mustang will not downshift from D to second above 50 mph, but, if I want to get some killer acceleration, I'll manually pull it down to second and nail the throttle. It'll usually pull up to about 70 mph in second. I've never gone faster before shifting back to D because I'm a coward and because it doesn't feel like there's a whole lot of reason to keep winding it.
Last edited by RagTop69; May 19, 2008 at 04:04 PM.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Had a 73 Olds 98 that I let a friend drive and he left it 1st and over rev'd it, thing jumped gears and would never shift into 2nd again, it would go from 1st to 3rd. Pretty sure it had a TH400 in it with the 455 Olds. Miss that boat...err I mean car.
