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| 904 Slips https://slantsix.org/forum/viewtopic.php?t=44954 |
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| Author: | newport77 [ Fri May 13, 2011 7:13 am ] |
| Post subject: | 904 Slips |
Guys I have a 75 Dart, slant 6 w/Super 6 intake and carburetor, and a 904 automatic. The problem I'm having with it is that, shortly after the engine is started cold (engine still in fast idle, though on one of the lower steps of the cam), shifting into Drive and just beginning to drive off, the transmission will "let go" and go into neutral for a second or two, even with light throttle pressure. I usually take my foot back off the gas and put it back on lightly, after which point the transmission operates normally in all ways. For a very long time now (many years) it has had a slight delay after shifting into Drive, not more than a second delay. I always had enough patience to wait until it went into gear and never hit the gas before it shifted. The fluid level is filled up- that I am sure of. For a while, a few years ago, it did have a leak at the end of the transmission where the driveshaft goes into it. I kept re-filling the fluid until the leak got worse and then replaced the seal at that end of the transmission. It hasn't leaked since. I converted to a Super Six over 10 years ago. The shift points on the transmission were different after I did it, so I adjusted the linkage back then, and the upshifts are at the right speeds/engine rpms- i.e. not too low or too high. Evidently there is a clutch or band or something unique to 1st gear that seems to be having a problem. What is going on here- Will a fluid change and a band adjustment correct this problem? Or is there something more serious that needs fixing here? I remember there being two band adjustments you could do- one screw was outside on the case and the other was only accessible when the pan, filter, an fluid are removed. I'm trying to take care of this before the problem gets worse and I wind up needing to have it rebuilt. In the meantime I have been using the car only occasionally until I can get this resolved. Thanks. |
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| Author: | Doc [ Fri May 13, 2011 9:25 am ] |
| Post subject: | |
A fluid & filter change would be the first step. You may want to try turning-up the transmission's main line pressure while the pan is off for the filter change. DD |
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| Author: | newport77 [ Fri May 13, 2011 10:05 am ] |
| Post subject: | |
OK, that sounds like a good idea. How do I turn up the main line pressure? Thanks. |
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| Author: | Doc [ Fri May 13, 2011 11:21 am ] |
| Post subject: | |
I would go a full turn on this transmission but to be honest, it is best to install a pressure gauge into the test port and take a pressure reading, prior to going into the trans... then adjust, based on that. The FSM describes the test & adjustment in detail. You will have to "cut-down" the allen wrench if you want to do the adjustment while the valve body is installed. DD 
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| Author: | newport77 [ Fri May 13, 2011 11:52 am ] |
| Post subject: | |
Thanks for the nice detailed photograph. OK- I will check the FSM! |
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| Author: | SlantSixDan [ Fri May 13, 2011 5:48 pm ] |
| Post subject: | |
Definitely do a fluid and filter change and a band and linkage adjustment. Turn up the line pressure a little if you want. But for now, the first thing to do is to change your cold-starting procedure. First thing, as soon as you get in the car, shift into Neutral (make sure the handbrake is set and that it is working). Then start up the car, then fasten your seatbelt and get ready to go. Once the engine's been running for 20 or 30 seconds, kick the accelerator to drop down off the fast idle cam's highest step, then shift into gear. See if that changes the car's behaviour and report back. |
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| Author: | newport77 [ Sat May 14, 2011 12:46 pm ] |
| Post subject: | |
Hey Dan- Thanks for the tip. I do give the car some time to warm a little bit before starting off. I have to pull the car out of the garage, go back and put the door down, etc... I make sure the fast idle is kicked down a bit before I go. The engine isn't racing super fast... It's probably dropped a step or two on the cam by then... I have to back out, it's fine in Reverse. It's just when I get out to the street (by which time the engine has been running for at least a minute) and put it into Drive- that's when I have the slip. Occasionally it won't slip right away, I'll go a little further up the road and make a turn; then after making the turn, it will go back into first (or possibly second now that I think about it, because I'd be going about 10 mph) and it will slip then. Either way it is fine once it warms up a little. It acts as if it's low on fluid, but it's not. I can warm it up even longer, but a minute should be long enough I would think. |
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| Author: | SlantSixDan [ Sat May 14, 2011 1:26 pm ] |
| Post subject: | |
Quote: I do give the car some time to warm a little bit before starting off. (etc.)
You're missing the point. The idea is to try warming it up in Neutral, not Park, and see if that changes anything.
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| Author: | Chuck [ Sat May 14, 2011 5:46 pm ] |
| Post subject: | |
Quote: The idea is to try warming it up in Neutral, not Park, and see if that changes anything.
Sorry if I'm a dummy, but what is the difference on that trans? On the push-button trans there is no difference.
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| Author: | SlantSixDan [ Sat May 14, 2011 7:06 pm ] |
| Post subject: | |
Quote: what is the difference on that trans? On the push-button trans there is no difference.
You're right on the pushbutton transmission and the cable-operated '65 unit: the only difference between Park and Neutral on those is that the parking pawl is engaged in Park and disengaged in Neutral. But starting in '66 with the rod-shift/single-pump Torqueflites, there's a difference between Park and Neutral: in Park there's no (or minimal) fluid flow to the torque conveter. In Neutral, there is full flow to the torque converter. The reason for starting and warming up in Neutral rather than Park is to check for (and costlessly compensate for, for a long time) the early-morning slippage being due to torque converter drain-down. If it makes no difference, he's got more serious issues to look at. If it makes a difference, it's an indication that the transmission will eventually need to be gone through...far in the future after a great many mornings of starting and warming for 20 seconds or so in Neutral rather than Park.
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| Author: | WagonsRcool [ Sat May 14, 2011 8:53 pm ] |
| Post subject: | |
That's why the fluid check procedure for linkage-shift torqueflights is to shift through the gears & end in neutral before pulling the dipstick. |
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| Author: | Chuck [ Sat May 14, 2011 9:28 pm ] |
| Post subject: | |
Thanks for the clarification! |
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| Author: | newport77 [ Sun May 15, 2011 8:48 pm ] |
| Post subject: | |
Thank you Dan for the explanation. I was not thinking there was a difference between Park and Neutral. I did not know that about the situation with the torque converter filling up vs. not filling up. I don't use this car a lot. Really only on the weekends, not on a daily basis. Also only when the weather is nice enough. I will try your method and see if it helps. It was just that it had never done this before until fairly recently. Well, I'll try it out the next couple of times I use it, and will report back. |
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| Author: | BUCKET 636 [ Thu Jun 21, 2012 7:36 pm ] |
| Post subject: | |
I got this photo from what it looks like to be the same source as the photo from Doc. It says to turn the screw counterclockwise to increase pressure. Am i missing something ? I will be having a go at adjusting the bands and line pressure soon on my 904 Torqueflite (push button auto,1963 Valiant). As this will be the first time i have done this procedure myself,i would like to get it right.  Cheers, Greg |
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| Author: | bigslant6fan [ Fri Jun 22, 2012 2:02 pm ] |
| Post subject: | . |
Further info in my "shift kit worth it for a daily driver" post I just bumped up from 1 1/2 years ago |
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