727 Slight Slipping From 2nd To 3rd

[JG71B]

Fairly low mile at about 70k miles on motor and trans. Did a basic band adjustment before it went in. Shifts great from 1st to 2nd. All stock so it's smooth. My problem is from 2nd to 3rd there is a slight slipping. I was never able to drive it before getting it so I don't know how it was prior to that. Cruising it is not so bad. It either does what it's supposed to or I may have to just take my foot off the gas slightly and it shifts perfectly. I noticed if I increase the kickdown pressure, 1st to 2nd winds out a little further as does the firmness of the shift and I have less slippage from 2nd to 3rd. Now I've done nothing g to this other than adjustment, seals, fluid/ filter and a finned pan. Could this be a band getting thin or bad? Were my adjustments overdone? It's the only issue with this trans. It has a cooler itself that also rhns into the radiator so heat isnt an issue BUT it seems to do it LESS when its "cold" This motor and trans came out of a late 70's cop car and untouched other than by me. With the slight slipping from 2 to 3 I'm a bit leary of winding second out full pedal ...any thoughts on this? Thanks!

 

[turbine68rt]

Do you have pic of your current throttle linkage setup? If the linkage is not moving in unison with your throttle, there won't be enough clamping force in the front clutch to prevent slipping under load in 3rd/direct drive. My guess is it's been driven with improper linkage adjustment for some time and the front clutch pack probably needs replacing or total rebuild/inspection. Do you also get any slipping in reverse?

 

[Darter6]

the front clutch pack probably needs replacing or total rebuild/inspection.

2 to 3 shift slip usually means this.^^^^^
Question, Are you manually shifting up or leaving it in drive ?
Sometimes this may be a valve body problem,sometimes.As in varnish sticking the valve. Fresh fluid as you stated may wash the valves clean. Just a shot in the dark.

 

[JG71B]

Do you have pic of your current throttle linkage setup? If the linkage is not moving in unison with your throttle, there won't be enough clamping force in the front clutch to prevent slipping under load in 3rd/direct drive. My guess is it's been driven with improper linkage adjustment for some time and the front clutch pack probably needs replacing or total rebuild/inspection. Do you also get any slipping in reverse?

I have a Lokar set up on a 1406 and a Weiand 8008. I'd take a pic but my camera app isn't working. It's in D 95% of the time, very seldom I run through them manually. No slipping in R. It idles at about 800 and feels a little stiff going into R actually but zero slipping. It's seems strong. I csn sit at the RR crossing on a decent hill and it will hold the car with no brake. 2 to 3 is the only issue and it's very slight but very noticeable fluid is fresh and to level hot. Would I possibly have gone too light on the band adjustment or that not necessarily related? Also, it doesn't seem to be getting worse. This is what makes me think its an adjustment issue

 

[turbine68rt]

The kickdown band is applied for 2nd gear.
If you are already noticing slipping on 2-3 you may want to do a teardown/inspection and verify that your kickdown setup is adjusted properly. When you reach full throttle is the throttle valve lever at max travel as well?

 

[JG71B]

The kickdown band is applied for 2nd gear.
If you are already noticing slipping on 2-3 you may want to do a teardown/inspection and verify that your kickdown setup is adjusted properly. When you reach full throttle is the throttle valve lever at max travel as well?

When I pull it out here in a bit I will double check where it's at at WOT.

 

[dvw]

Easy check. Force the throttle pressure arm all the way back with a zip tie or what ever. It will now shift very late. Go hammer it wide open. Did it slip? If so there is either loss of pressure to the forward (3rd/rev) clutch circuit. Or the clutch fibers are toast.
Doug

 

[Dave6T4]

I am guessing varnished/burnt front drum clutch discs. Steelies likely burnt as well.

 

[JG71B]

I did push the throttle all the way back and there was a small amount to go for the pressure switch to be engaged all the way. I did however add a small amount of pressure and have the 2 to 3 shifts feeling good with no slipping but, my shift points are a little higher than normal and the kickdown doesn't engaged unless I'm doing around 40 or less. Right now it's shifting from 2 to 3 at around 25-30mph. Would the Lokar set up not have the same rate of pull on the trans than the throttle??

 

[66 Sat]

I had (have) the exact same issue. It's only in D, not when I shift manually and only under certain conditions (transmission hot, maybe 1/3rd throttle). Doesn't do it under full throttle, half or under very light throttle.
It's almost like an overshift, like 2 and 3 are engaged at the same time.
For me it's 100% related to the kickdown adjustment. I've got rid of it in the past but recently I swapped carbs and now the adjustment is slightly out and it's doing it again.
It doesn't help that there's lots of slop in the factory kickdown with all the different joints.

 

[dvw]

2/3 overlap is common in modified valve bodies. How ever it won't slip. It'll feel very harsh. If the trans slips on the 2/3 at light throttle you have one of the issues listed in post #7. A quick overview of TF operation. You will see the rear clutch is applied in all forward gears. If any forward gears function correctly, It's OK. You will also note the KD band is only applied in 2nd gear. If 2nd functions properly it's OK. The front clutch is applied in 3rd and reverse. However the line pressure in reverse is over double compared to wide open throttle in 3rd. If it slips un 3rd the problem is with that clutch. This clutch can be damaged from hard piston seals, worn reaction shaft supprt rings, worn reaction shaft ring groves, low throttle pressure from improper linkage adjustment, not enough clutches for the power application (3 clutches are borderline for higher power street stuff). Low overall line pressure, water in fluid would likely damage other components. A damaged clutch pack will not repair itself.
Doug

 

[Dave6T4]

Somehow, I totally missed the Lokar cable reference. Based on my experiences with this system, it could be the cause of the problems. The kickdown lever attachment point and the throttle lever attachment point MUST go through the same 1:1 distance of travel to work correctly. There can be a bit of experimentation and drilling of different attachment holes to achieve this critical range of motion. If the car was driven much with the cable misadjusted, the front clutch pack could be damaged.

 

[JG71B]

I appreciate the replies. It seems to like where it's at. I am going to keep an eye on it and see how it goes. I haven't had to light foot it at shifts or any of that. It's been really smooth and consistant. If it's headed for rebuild then I won't really hurt anything. I'm not beating on it all the the time. I was already wondering if the ratio was the same for the throttle and kickdown points. We'll see how things go for a minute

 

[oldkimmer]

How many turns is the front band at? Do u have the right arm on the carb? Post pics of the linkage. Kim