Turbo 400 won't downshift
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Joined: Mar 2011
Posts: 66
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From: Valencia CA
Turbo 400 won't downshift
OK, so the Turbo 400 in my '75 won't downshift on its own. Here's the history. When I bought the car it wouldn't downshift on it's own, but did if I manually downshifted. I found that one of the wires to the switch under the dash was broken. So I slapped on one of those crimp-style connectors, and it was fixed. It has worked fine for almost 2 years.
Now, all of a sudden this week, it stopped downshifting again, and when I keep it floored it upshifts way too soon. Before this problem started, it would upshift at redline if I was floored.
I checked that switch, and it seems fine (maybe the connector is crap?), and that same switch operates the little cold-air flapper in the hood. So I'm pretty sure the switch is still good. I checked under the car to make sure the wire was still connected to the trans and not melted on the exhaust. I even checked the fluid level. Everything checks out.
So any suggestions?
Thanks,
Now, all of a sudden this week, it stopped downshifting again, and when I keep it floored it upshifts way too soon. Before this problem started, it would upshift at redline if I was floored.
I checked that switch, and it seems fine (maybe the connector is crap?), and that same switch operates the little cold-air flapper in the hood. So I'm pretty sure the switch is still good. I checked under the car to make sure the wire was still connected to the trans and not melted on the exhaust. I even checked the fluid level. Everything checks out.
So any suggestions?
Thanks,
Burning Brakes
Joined: Apr 2010
Posts: 1,018
Likes: 9
From: Winston Ga.
the only thing that switch does is actuate the hood intake...
see hood solenoid at the top then follow it back to the switch one way and ground the other. Although its off this pic, the other side of that switch is the fuse box.
[IMG]
[/IMG]
Keep looking for the downshift issue. its a coincidence that it started working before.
I would suspect a vac leak? isnt there supposed to be a vac line to the tranny to downshift. I dunno, mine a 4spd
see hood solenoid at the top then follow it back to the switch one way and ground the other. Although its off this pic, the other side of that switch is the fuse box.
[IMG]
[/IMG]Keep looking for the downshift issue. its a coincidence that it started working before.
I would suspect a vac leak? isnt there supposed to be a vac line to the tranny to downshift. I dunno, mine a 4spd
Last edited by jnealg; Jul 4, 2013 at 12:40 AM.
Burning Brakes
Joined: Apr 2010
Posts: 1,018
Likes: 9
From: Winston Ga.
hey I could be wrong, pm me your addy and I will send the wiring scats. you should be able to find it and follow where it goes.
since you are so sure, you have my curiosity peaked now. post up your findings.
since you are so sure, you have my curiosity peaked now. post up your findings.
Last edited by jnealg; Jul 4, 2013 at 01:44 AM.
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Those free schematics are good 99% of the time, except in this case you have to go to the service manual.
Burning Brakes
Joined: Oct 2001
Posts: 1,241
Likes: 4
From: Okinawa Okinawa
Kickdown switch shouldn't have anything to do with the normal downshifting of the tranny.
Does it have the proper amount of fluid? Make sure the hose didn't come off the modulator on the pass side of the tranny.
Does it have the proper amount of fluid? Make sure the hose didn't come off the modulator on the pass side of the tranny.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If upshifts are coming early, it's likely that your governor valve is stuck. That valve is in the shaft of the governor unit. Remove the side cover (left-rear) and twist/pull out the governor. Look into the feed slots on the gov shaft as you move flyweights in/out. The valve in the shaft should move freely with movement of the weights. If it's stickly, you can try to flush out any sediment/debris. If you notice any small metallic particles in the tranmission oil (as you remove the gov), you may be at the onset of an internal failure of the tranny. Any debris in the oil will begin to stick various valves in the transmission.
If it has been a while since changing the oil & filter, you might try that before you put it back together.
If it has been a while since changing the oil & filter, you might try that before you put it back together.
Last edited by 7T1vette; Jul 4, 2013 at 09:55 AM.
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