OK, heres the scoop. Pretty lengthy. 78 Malibu drag car with relatively mild 355. Wednesday night at Test & Tune my first pass went fine shifting manually at 6000 rpm. Ran a best ever time of 12.56, however, when I slowed down and turned onto the return road, my car was then in 3rd gear and when I gradually pressed on the gas to go, the engine revved but little or no movement. I manually shifted down to 2nd, same thing. My stomach begins to feel nausious. I stop and pull it down into 1st. No problem. I manually shift into 2nd, trans did not shift, stayed in 1st. Stop got time slip and proceeded to drive off in 1st. Shifted to 2nd, and trans shifted, shifted to 3rd, and trans began to slip. Got back to pit and looked at fluid. Very low. Added 2 quarts and fluid measured fine on stick. Made a second hard pass with what seemed to be no slipping, but car did slow to a 12.61. Possible slippage. Any thoughts on what is happening and what to check ?
You didn't say if anyone reported smoke during that first run. If you're running a vacuum modulator it's possible that it blew a diaphragm and the fluid was sucked into the intake. However, that problem wouldn't have fixed itself and you should see obvious smoke and continued loss of fluid.
If anyone else has an idea to offer think about this one while you're at it. My 350, occasionally, burps about a cup of fluid out of the vent. It only does it after the car has sat for a week or two and only in reverse. If I back into the garage and pull out I don't see this problem and it never does it when the car (tranny) is warm, only on cold starts.
The line to the vacuum modulator is plugged. I shift manually. My son said he did not see any smoke during the run or after. Stumped that it shifted fine during the run but not at slow speeds. Thanks for the reply.
Being low on fluid will starve the valve body and cause a cavitation in the pump....not a good thing to do. Reason, you will fry your clutch pack and once you heat those clutches up and glaze their faces, they will not grip the plates in between the clutch disc. Thus, no fluid to cool or offer any traction to the bands and clutch packs. Once you start cooking those clutch packs, you might as well start getting the parts ready for a rebuild. Plus if you run the pig on low fluid and go into a real quick turn, you will cavitate your pump and blow that one all to hell as well. I would recommend adding a fluid pressure sensor to the transmission if you plan on racing it all the time.
Good luck with this one, and keep your fluids topped off befor you launch down the track. Last thing you want, is at the end of the run and that return trip, is to be sitting there at 1500rpm and no go power.
Make the investment and beaf up the transmission soon, sounds like you may not have any choice sooner then you think.
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