Make sure you have vacuum going to the vacuum modulator, so check for vacuum leaks, and make sure you are not idling too fast, idle speed is probably around 500 rpm. Good Luck.
Violent Jolt Going From Park Into Drive And Reverse
I have a 70 Mach 1, FMX auto transmission and there is a violent jolt when I go from Park into drive or reverse, it's worse when the car is warm, ie it doesn't happen when i'm reversing the car out of my garage, apart from that the gears shift great when driving, there is no knocking or delays when going through the gears, i've currently got the car booked in with a Mustang specialist as I had to have the carb rebuilt, but any ideas what the problem could be, do you think the transmission could need rebuilding? I sure hope not, we've got a new modulator valve on order as that is the cheapest option at the moment, thanks for any help
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also check u joint and transmission mounts.
have you ever had any work done on the transmission?
I hard shift could be the result of worn clutch packs, if there isn't good contact there could be a harsh shift.
Also I agree with the above post. If the vacuum level is high,(as if the motor was under a heavy load) it would cause hard shifts and late shift response as if you were flooring it.
The transmission could need to be rebuilt...
I hard shift could be the result of worn clutch packs, if there isn't good contact there could be a harsh shift.
Also I agree with the above post. If the vacuum level is high,(as if the motor was under a heavy load) it would cause hard shifts and late shift response as if you were flooring it.
The transmission could need to be rebuilt...
Thanks for the replies, as I said though it shifts fine when driving, it's only going from park to drive or reverse it jolts, surely if the transmission needed rebuilding it would jolt when driving?
I have the same problem with the C4 in my '66. The u-joints are quite new, the transmission was rebuilt, so I know it is not these causing the sledgehammer shift. There's no shift kit in my C4 either, so it ain't that.
I do notice a delay in dropping into either R or D, so it leads me to believe it could be the servos or the seals on the servos. I haven't bothered to crawl under the car and mess with it, as I am overseas most of the year and would just rather drive the damn thing as opposed to tearing it down.
Hope that helps.
I do notice a delay in dropping into either R or D, so it leads me to believe it could be the servos or the seals on the servos. I haven't bothered to crawl under the car and mess with it, as I am overseas most of the year and would just rather drive the damn thing as opposed to tearing it down.
Hope that helps.
High idle, loose joints and bad mounts can cause severe shifts from park. There is nothing in the transmission that will cause it.
Ok thanks all, much appreciated
To echo comments above, simplest and most likely culprit is high idle. Shifting into drive or reverse means you are at a stop, presumably idling.
Before you do anything else, turn the idle screw on your carburetor down just a bit -- you may need to adjust the mixture screw also, but most likely not. Then try your start-off shifts. If they're still jolting, try the other solutions suggested above.
Good luck.
Before you do anything else, turn the idle screw on your carburetor down just a bit -- you may need to adjust the mixture screw also, but most likely not. Then try your start-off shifts. If they're still jolting, try the other solutions suggested above.
Good luck.
Well we've lowered the idle and it has got a little better but is still there, we've replaced the modulator valve, also checked the U Joints and mounts and everything is fine, so i'm lost really?
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