Tranny in drive causes engine racing.
- Thread starter indyman13
- Start date
Vin Man
Famous Member
When you put it in R, does it go backwards with no problem?
I would suspect the torque converter if you are sure your tranny fluid levels are fine.
The other thing to consider would be a worn out yoke on the driveshaft. When you put it in gear and give it gas, does it move at all?
I would suspect the torque converter if you are sure your tranny fluid levels are fine.
The other thing to consider would be a worn out yoke on the driveshaft. When you put it in gear and give it gas, does it move at all?
'68falconohio
Well-known member
A vac leak will make it rev up, right? I don't know much about automatic trans. but does the modulator valve only 'work' when the trans is in drive, 2, and 1? Could it be a vac leak there leaning out the mix and causing the engine to rev up?
It would be easy to check by plugging the line that goes to modulator valve and seeing what happened.
I'm thinking out loud and do not have any experience with a mod. valve vaccum leak causing this or causing this problem. Only a thought.
It would be easy to check by plugging the line that goes to modulator valve and seeing what happened.
I'm thinking out loud and do not have any experience with a mod. valve vaccum leak causing this or causing this problem. Only a thought.
Transmission is working just fine. Shifts smooth and everything. No problems in reverse.
When I'm driving and slow down and am just about stopped it will rev up. I'll let my foot off the brake and it picks up speed (no foot on accelerator) to about 2000 rpm then settles back down to about 800-1000rpm.
When I'm driving and slow down and am just about stopped it will rev up. I'll let my foot off the brake and it picks up speed (no foot on accelerator) to about 2000 rpm then settles back down to about 800-1000rpm.
A little history. Tranny was behaving a little strange on occasion on two of the last half dozen drives. Would slip out of drive and nothing. Would run it through the PRNDL settings and things went back to working normally. Last four drives over the past week no problems at all.
Wanted to change valve cover gasket and do a little cosmetic work under the hood. Labeled all vacuum lines, removed carburetor and all linkage, kick down lever, etc.
Put it all back together started her up just perfectly. Backed out of garage, no problems. Shifted into drive and the devil that's possessed her took over. Once on the road it shifted fine through all the gears. Slowed down to stop at an intersection and as soon as I got down to about 3mph it revved up again and had to keep my foot on the brake to keep from really taking off. Would let it carry itself without touching accelerator and it would level back off only to rev back up again when slowing down.
Got home, looked under car and saw transmission fluid on one of the vacuum lines coming from manifold. Knowing there shouldn't be any fluid in a vacuum line I removed the modulator. It had fluid in it so I'm at least recognizing a bad modulator? It's the two line modulator.
I guess the modulator is magic since it's not hooked up to the dizzy, carb or anything. Just the two lines (the big one directly to one of the two largest inlets on the triple vacuum manifold under the carb, the smaller one to the firewall to a plastic fitting. That plastic fitting has a vacuum line going back to the smallest inlet on the triple manifold) The third (a large one) goes directly to my vacuum canister.
The more I think about the modulator and if it's controlling the load placed on the motor through the torque converter? then some kind of "input" is being sent to something that raises the rpm's.
I'm good at making a long story longer and just proved it. If a picture is worth a thousand words, was my thousand words worth a picture?
Thanks in advance to all of you for any insight on how all this stuff works together.
Wanted to change valve cover gasket and do a little cosmetic work under the hood. Labeled all vacuum lines, removed carburetor and all linkage, kick down lever, etc.
Put it all back together started her up just perfectly. Backed out of garage, no problems. Shifted into drive and the devil that's possessed her took over. Once on the road it shifted fine through all the gears. Slowed down to stop at an intersection and as soon as I got down to about 3mph it revved up again and had to keep my foot on the brake to keep from really taking off. Would let it carry itself without touching accelerator and it would level back off only to rev back up again when slowing down.
Got home, looked under car and saw transmission fluid on one of the vacuum lines coming from manifold. Knowing there shouldn't be any fluid in a vacuum line I removed the modulator. It had fluid in it so I'm at least recognizing a bad modulator? It's the two line modulator.
I guess the modulator is magic since it's not hooked up to the dizzy, carb or anything. Just the two lines (the big one directly to one of the two largest inlets on the triple vacuum manifold under the carb, the smaller one to the firewall to a plastic fitting. That plastic fitting has a vacuum line going back to the smallest inlet on the triple manifold) The third (a large one) goes directly to my vacuum canister.
The more I think about the modulator and if it's controlling the load placed on the motor through the torque converter? then some kind of "input" is being sent to something that raises the rpm's.
I'm good at making a long story longer and just proved it. If a picture is worth a thousand words, was my thousand words worth a picture?
Thanks in advance to all of you for any insight on how all this stuff works together.
:duh: :duh: :duh:
Problem solved-----I fell like a dunce. Not vacuum leak, not modulator.
I fabricated a new throttle cable bracket and braced it to the shock tower brace. When engine was placed in drive it torques itself over a little and engages its own throttle since the bracket doesn't move with the engine as original.
Got it bracked back to the engine now and everything is hunky dorry.
DOH!
Problem solved-----I fell like a dunce. Not vacuum leak, not modulator.
I fabricated a new throttle cable bracket and braced it to the shock tower brace. When engine was placed in drive it torques itself over a little and engages its own throttle since the bracket doesn't move with the engine as original.
Got it bracked back to the engine now and everything is hunky dorry.
DOH!
I misunderstood the original problem. I thought it was the tranny spinning up, not the engine.
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