727 trans shifts too hard

[furyus2]

Hello, I have a TCI valve body in my Dart. I'm a little older now, and I think it shifts too hard, especially on downshift. I was wondering if i put the accumulator spring back in, would that soften the shifts some? Thanks.

 

[brian6pac]

maybe 1-2 up shift

 

[oldkimmer]

Yes U could lower the line pressure some also. Kim

 

[70aarcuda]

Is it a manual valve body?....I think some of them do not use the accumulator...

 

[AJ/FormS]

Years ago the kits would block the piston or tell you to put some monster spring in there. I never liked that even when I was half as old as I am today. I ransacked my cores and found about three different ones. It took two tries to find one that I liked.
Good luck,and happy hunting.

 

[furyus2]

Is it a manual valve body?....I think some of them do not use the accumulator...

Not a manual Vb. Just the firm shift type.

 

[furyus2]

Years ago the kits would block the piston or tell you to put some monster spring in there. I never liked that even when I was half as old as I am today. I ransacked my cores and found about three different ones. It took two tries to find one that I liked.
Good luck,and happy hunting.

So, do you mean it will soften the shifts? My main concern is the automatic downshift is harsh. Would replacing the spring, or decreasing line pressure soften the downshift?

 

[LJ67barracuda340]

in the early eighties my 727 with a Street Trans Go shifted so hard it broke the end off the band and the servo piston almost went thru the bottom of the pan. I bought a new band and the trans guy said "drill a 1/8 hole in the piston, it'll bleed off some of the pressure." I did and it would slip from drive to reverse to drive almost like when it was stock, it shifted firm but not hard normal driving, but it would still chirp the tires under power. piston is still in there today.

 

[furyus2]

in the early eighties my 727 with a Street Trans Go shifted so hard it broke the end off the band and the servo piston almost went thru the bottom of the pan. I bought a new band and the trans guy said "drill a 1/8 hole in the piston, it'll bleed off some of the pressure." I did and it would slip from drive to reverse to drive almost like when it was stock, it shifted firm but not hard normal driving, but it would still chirp the tires under power. piston is still in there today.

Was that the front piston, or rear? Does it matter where on the piston you drill the hole?

 

[TrailBeast]

Just back down the throttle pressure adjustment.
It' will soften ALL the shifts, up and down as well as make all upshifts a bit sooner.

 

[oldkimmer]

It's the rear piston Try what TB says it may get u where u want to be. Kim

 

[AJ/FormS]

There are three basic pressures in the VB, and some of them fight each other, and some combine . The three are called line pressure, throttle pressure, and governor pressure.
The line pressure sets the stage to make the guts take abuse, affects shift quality and opposes governor pressure.. Cranking the pressure up causes increased holding power for the clutches and bands. A side effect is harsher and later,shifts
The throttle pressure augments the line pressure to shuffle the shift from early to late, and makes the shifts slightly harsher with later shifts. Or actually if you set it up right, reduces the harshness to make normal driving bearable.
When the driveshaft is turning, the governor pressure is always fighting the other two, trying to accomplish a shift.The governor pressure is much affected by driveshaft rpm. That means 4.10 will command a shift much sooner than 2.76s. To counter this, there are several different flyweights available to get this tuned up.
The upshot of all this is Line pressure sets the stage, and the TP modifies it with the gas pedal.
So TB has it right, crank the T-P down, and see if it is more bearable.
As for me, I would get inside and reduce line pressure a tad, plus experiment with accumulator springs. If the shifts become too early, I would reduce the governor flyweight mass, or experiment with the little spring inside it. This, however is very time consuming. And not any fun at all to do in your driveway. So backing off the TP via the KD link is always #1,I guess.
Also the KD link at the carb should have a spring on it such that the link follows the throttle butterflies. This will reduce TV pressure directly with the gaspedal. If the link is allowed to float, sometimes it runs late and the pressure stays high.And then automatic downshifts are harsher than they need to be.

To make line pressures easy to adjust, I drilled and tapped the tranny case in just the right spot to insert the correct sized allen wrench. Now It's a 10 minute deal and most of that time is spent backing up the rear end onto a curb, so the oil moves to the passenger side, and so I can get under the beast.lol

 

[furyus2]

Thanks! this is what I wanted to know. Currently I backed off on the TP, and it shifts too soon now, but still harsh, with the harsh downshift. I will make sure the TP follows the throttle. Then the line pressure. Right now, it shifts way too soon when the pedal is floored. I think I am going to end up in the governor at some point, but since it's a pain, I'd rather optimize the adjustments. I like the idea of drilling the case. I hope this sounds like the way to proceed. Correct me if I'm wrong.....

 

[TrailBeast]

Thanks! this is what I wanted to know. Currently I backed off on the TP, and it shifts too soon now, but still harsh, with the harsh downshift. I will make sure the TP follows the throttle. Then the line pressure. Right now, it shifts way too soon when the pedal is floored. I think I am going to end up in the governor at some point, but since it's a pain, I'd rather optimize the adjustments. I like the idea of drilling the case. I hope this sounds like the way to proceed. Correct me if I'm wrong.....

The gov only changes when it shifts, not how firm necessarily.
The oil flow through the separator plate in the valve body is where you need to slow the oil flow so engagements are softer.
Those oil ports are often drilled larger to allow fast apply of bands and clutches, so you may actually want to swap your valve body to someone who wants the firmer shifts.
Of course there are other ways of doing it, but it would require a lot more work and disassembly of the valve body.
I have seen valve bodies with small cotter pins in those drilled holes to slow the fluid and therefore slow the apply when someone over drilled them.

If it were me I would leave or change the pressure to what it should be, and deal with what makes it too firm.
If you lower the line pressure you will be lowering the holding pressures of the bands and clutches also, and that could cause damage from slipping under load.
It will also make your shifts way late, because lowering the pressure causes the shift valve springs to need more pressure to move and therefore it waits until the governor can't resist it any longer so you basically end up with the same problem because you would lower the TP to try and compensate for the late shifts and in turn lessen the holding power even more, but still have a high fluid flow causing it to still be harsh in shifting.

Raising line pressure will cause it to shift early for the same reason on the shift springs, but it would still be harsh from the lack of the accumulator spring, and still having oil flowing to the bands and clutches at a raised rate (still harsh) because of the drilled holes in the separator plate and having to raise the TP to make them later again after raising the line pressure.

This is what AJ was saying about the pressures being opposed by other pressures.
I really feel you need to slow the apply by limiting the flow to the clutches and bands, and put an accumulator spring back in it.
Either that or swap back to a more stock valve body and spring and let the younger guys have the real firm shifts. (a lot less work) to get what you want.

Now, if you swap valve bodies you will need to take a good look for and remove any orifice plugs that may have been put in the case due to the shift kit instructions, and will if there are any they need to be removed when going back to a more stock valve body. (easy enough by screwing a deck screw into them and pulling them out)

JMO

 

[furyus2]

The gov only changes when it shifts, not how firm necessarily.
The oil flow through the separator plate in the valve body is where you need to slow the oil flow so engagements are softer.
Those oil ports are often drilled larger to allow fast apply of bands and clutches, so you may actually want to swap your valve body to someone who wants the firmer shifts.
Of course there are other ways of doing it, but it would require a lot more work and disassembly of the valve body.
I have seen valve bodies with small cotter pins in those drilled holes to slow the fluid and therefore slow the apply when someone over drilled them.

If it were me I would leave or change the pressure to what it should be, and deal with what makes it too firm.
If you lower the line pressure you will be lowering the holding pressures of the bands and clutches also, and that could cause damage from slipping under load.
It will also make your shifts way late, because lowering the pressure causes the shift valve springs to need more pressure to move and therefore it waits until the governor can't resist it any longer so you basically end up with the same problem because you would lower the TP to try and compensate for the late shifts and in turn lessen the holding power even more, but still have a high fluid flow causing it to still be harsh in shifting.

Raising line pressure will cause it to shift early for the same reason on the shift springs, but it would still be harsh from the lack of the accumulator spring, and still having oil flowing to the bands and clutches at a raised rate (still harsh) because of the drilled holes in the separator plate and having to raise the TP to make them later again after raising the line pressure.

This is what AJ was saying about the pressures being opposed by other pressures.
I really feel you need to slow the apply by limiting the flow to the clutches and bands, and put an accumulator spring back in it.
Either that or swap back to a more stock valve body and spring and let the younger guys have the real firm shifts. (a lot less work) to get what you want.

Now, if you swap valve bodies you will need to take a good look for and remove any orifice plugs that may have been put in the case due to the shift kit instructions, and will if there are any they need to be removed when going back to a more stock valve body. (easy enough by screwing a deck screw into them and pulling them out)

JMO

Thanks again. I don't think I want to have it shift like stock, just want to tame it some. I will try the ideas I've been given, and report back. It may be a while, i have to do a disc brake swap first.

 

[AJ/FormS]

In the past, when I have reduced the line pressure, this allowed me to run more TV pressure, to get back the clamping, but Now the harshness can be controlled by the gaspedal. Be forewarned tho that lift-foot upshifts can surprise the heck out of you,lol.
I agree with TB on all points,
not that that means anything,lol.

But I just gotta say that if you get right, you can upshift/down shift with gaspedal, and that gets to be really fun;
Bwhaah-haaaaaaaaaaaaaw..... Bwhaah-haaaaaaaaaaaaaw....

 

[TrailBeast]

In the past, when I have reduced the line pressure, this allowed me to run more TV pressure, to get back the clamping, but Now the harshness can be controlled by the gaspedal. Be forewarned tho that lift-foot upshifts can surprise the heck out of you,lol.
I agree with TB on all points,
not that that means anything,lol.

But I just gotta say that if you get right, you can upshift/down shift with gaspedal, and that gets to be really fun;
Bwhaah-haaaaaaaaaaaaaw..... Bwhaah-haaaaaaaaaaaaaw....

It's means something to me when you agree with me.
It means we both somehow still remember what we learned.

The comment about shifting with the gas pedal is pretty much on the nose and it is a blast when you get it.
Before I changed transmissions my 318/904 was like that after I added the part throttle kickdown and would downshift at about 1/3 throttle from 3 to 2 if I was doing under 35.
On a mild hill in the road I could get it to kick down to second easily at in town speeds, and it shifted right where I would have manually if I just left it in drive.

Now after the 42RH and the Magnum engine install with the shift kit the Wife asks why I manually downshift since it's an automatic.
I have to do it manually or get into the throttle more than I like for general driving in town.

And yea, those lifting the foot shifts can be real bell ringers.

 

[AJ/FormS]

Hyup,lol