Shifting an automatic
Race Director
Joined: Mar 2008
Posts: 15,161
Likes: 17
From: coffee
I wish that the megashifters were an easier install, I read a thread or two about a cople of guys that did this on their C3's and it looked fairly involved, still might give it a shot someday though that is way down on the list of to-do's.
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
No different than shifting any other trans manually....be smart at what RPM you do it....up or down.. the biggest concern is downshifting at too high RPMs
Thread Starter
Racer
Joined: Aug 2007
Posts: 414
Likes: 0
From: Quincy MA
Yeah I won't be man-handling it while downshifting...It's not like I was 20 once with a brandeeeeenew Camaro' that I had Supertrapp's put on off a Y-pipe and downshifted at every possible moment to hear them gurgle unless the stereo was up too loud hahaaa...coincidentally blowing the tranny 6K before the warranty was up!! When I picked it up I asked is it bad to downshift at 80 into second??
But I concead I am a much better driver now and heck; more responsible...
K.O.
But I concead I am a much better driver now and heck; more responsible...
K.O.
Last edited by kmobrien76; May 16, 2008 at 07:22 PM. Reason: a
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I think the '74's still had the THM400 in them. The 400's had downshift overspeed inhibitors and upshift overspeed limiters.... you really can't do much damage to a 400 by manually shifting it. It you downshift at too high a speed, the inhibitor will just prevent the downshift until the rpm is low enough. Shoot, you can just leave it in 1st and wind the snot out of it...it should just shift into 2nd on its own when wound high enough. [I used to do that a bunch, back in the day....probably not a great idea with a 40 year old tranny, though.]
Thread Starter
Racer
Joined: Aug 2007
Posts: 414
Likes: 0
From: Quincy MA
The guy that I bought it from said I could do that and it would upshift into 2nd itself and the shifter would actually move, true or untrue??
Kevin
Kevin
I think the '74's still had the THM400 in them. The 400's had downshift overspeed inhibitors and upshift overspeed limiters.... you really can't do much damage to a 400 by manually shifting it. It you downshift at too high a speed, the inhibitor will just prevent the downshift until the rpm is low enough. Shoot, you can just leave it in 1st and wind the snot out of it...it should just shift into 2nd on its own when wound high enough. [I used to do that a bunch, back in the day....probably not a great idea with a 40 year old tranny, though.]
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Thread Starter
Racer
Joined: Aug 2007
Posts: 414
Likes: 0
From: Quincy MA
I thought so, figured it sounded "different."
So from a technical standpoint, if I put it in 1st, nail it, and it automatically shifts to second then how does that work internally if the shifter is still in first, just curious if anyone knows...
Kevin
So from a technical standpoint, if I put it in 1st, nail it, and it automatically shifts to second then how does that work internally if the shifter is still in first, just curious if anyone knows...
Kevin
I'm hoping to learn something here, I thought if the shifter was in 1st and starting from a stop, it would never shift unless I moved the shifter.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
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.
Burning Brakes
Joined: Mar 2008
Posts: 1,038
Likes: 39
From: Denver, CO
St. Jude Donor '08-'09-'10
i have had to downshift cars manually before because of brakes going out... that and using the e-brake. it wont hurt the tranny. if it would, then why would they make it possible to shift yourself?????
anyways, you should be able to down/up shift at almost any rpm. but be careful and dont blow the tranny, as previously mentioned.
anyways, you should be able to down/up shift at almost any rpm. but be careful and dont blow the tranny, as previously mentioned.
Burning Brakes
Joined: Aug 2006
Posts: 1,155
Likes: 0
From: San Diego California
Shifting an automatic makes the vette a lot more fun to drive. Installing a Transgo shift kit to firm up the shift points is one of the best improvements I've done. I've been pretty aggressive with my TH350 trans- with 95K miles on it, and no problems.
