Hello,

It appears my transmission is slow to shift into high. I log transmission pressure and it shows that it takes .33 seconds between when then pressure drops and recovers. I get my pressure at the servo cover. Just curious if anyone has any comparable data to offer.
I also see a correlating dip in gforce over this time.

I am going to replace the shifter cable and air solenoid as they have been in there a while. Shifter seems to move freely over wise, but I may take it a part to give it a good cleaning.

May stick a camera on the shifter to see if something weird is going on.

If this doesn't change anything, I will try to shift it manually to see if it changes anything.

Thanks in advance

I chased this on my TD trans, shifter and and cable have nothing to do with when the pressure drops to when it rises back up, this is when the band is released and the cavity behind the high clutch piston fills. I also had an RPM flare on mine. Tightening the band from 4 turns out to 3 and also tightening the clutch pack clearance helped. mine takes about .02 to shift now. My pressure is about 275. I also installed an adjustable pressure modulator from Coan in the valve body so I could get my pressure where I wanted it

This message has been edited. Last edited by: Big Steve,

I once had a shifter break at the point where the cable attaches to shifter under the cover on that pin. chased it for acouple weeks til I noticed the pin was hanging on by a sliver of metal and wasn't allowing the cable to fully engage the trans into high gear. worked fine driving around pits but going down track was a different story. It may not be the answer to your problem but its something easy and free to check!

I was manually activating the air solenoid, and if I didn't push it hard, there was definitely a difference in how fast the shifter moved from first to second.

In my situation, it seems the band is slow to release, i would see drop off in gforce, and sometime the rpm seemed to go flat before it dropped off. It would be different at times, but I used to think it was an anomaly with the logger

My pressure is at 230 going down the track

I have the sonnax supported covers and spring. It say in the instructions, that I can play with the band adjustment to quicken the release. More turns out will enable a quicker release due to it sets the piston deeper in the case, thus more release spring pressure. I may try turning out a turn. Hopefully it doesnt cause the car to rock when going on the brake.

How are you measuring the shift time?

quote:

Originally posted by excessive braker:
I once had a shifter break at the point where the cable attaches to shifter under the cover on that pin. chased it for acouple weeks til I noticed the pin was hanging on by a sliver of metal and wasn't allowing the cable to fully engage the trans itypnto high gear. worked fine driving around pits but going down track was a different story. It may not be the answer to your problem but its something easy and free to check!

What symptoms did you experiance?

quote:

Originally posted by banjo:

In my situation, it seems the band is slow to release,

My pressure is at 230 going down the track

I have the sonnax supported covers and spring. It say in the instructions, that I can play with the band adjustment to quicken the release. More turns out will enable a quicker release due to it sets the piston deeper in the case, thus more release spring pressure. I may try turning out a turn. Hopefully it doesnt cause the car to rock when going on the brake.

I was told just the opposite by more than one trans builder. The further out you turn it means it may take fluid away from the high clutch piston making the problem worse. unless you have a leak somewhere you need to make the area behind both the high piston and servo piston smaller so they fill faster.
What is your clutch pack clearance?

Slow/long to shift into high gear and causing what I thought was the transmission slipping and revving up over my projected shift point. I cant find my video at the moment but you could see the shifter move into high gear and it not actually go into high. I had a quarter stick shifter. like I said may not be your issue but its a simple quick thing to check. pull the shifter cover and take the cable off the mounting pin and see if there is any play in that pin where it is attached to the shifter.

Read this thread I had on Yellow bullet on the very subject, lots of good info in it

https://www.yellowbullet.com/f...thread.php?t=2562981

Forward clutches are set at .090. But last time I rebuilt it, I found I had screwed up and on had it a out .040. No difference in this situation.


I will check out that link.

quote:

Originally posted by banjo:
Forward clutches are set at .090. But last time I rebuilt it, I found I had screwed up and on had it a out .040. No difference in this situation.


I will check out that link.

I thought mine were at about .088 until I got a old sun gear flange and notched it so I could fit feeler gauge in to check. Found I was over .120 when clutches were compressed. In addition to going from out 4 to 3 on the band adjustment and clutches now set at .072 the flare is gone and problem solved

The other thing to remember is our cars are apples and oranges, my car make over 2K hp and will run in the 3.8x range in the 1/8th making it way more sensitive to issues like this. If it is shifting exactly the same every run and your not burning the clutches it might not even be worth chasing this issue on you car.

quote:

I log transmission pressure and it shows that it takes .33 seconds between when then pressure drops and recovers

i dont have that capability,but from peak rpm in first to drop back rpm i am at 1.75 to 1.9

From peak rpm to the fallback I am .66 seconds.

I would like to see what others shifts look like, if you have some data logs you could post, I would be curious to see.

Thanks

I had this same issue with the sonnax servo, ended up completely disassembling it and found a bunch of muck back behind the piston where it slides in and out of the cover. Once I cleaned that out, the issue went away.

I just rebuilt the tranny about 6 months ago. This condition hasn't changed. There was a good but of muck in there, but after 500 passes you would expect it.

That is why I was thinking something with the shifter.

Thanks

quote:

posted April 20, 2019 08:32 AM Hide Post
From peak rpm to the fallback I am .66 seconds.

I would like to see what others shifts look like, if you have some data logs you could post, I would be curious to see.

i will try

i have rpm pro ,what is a good way to post graph

i cant figure out how to get my file to this site,lol

Take a screenshot(printscreen), and pasted into paint. Save it as a jpeg. You will then have to upload it to a picture hosting sight, if you dont have one, PM me and I will give you my email and posted it for you.

Thanks

Here is mine, you can see the huge RPM flare from when the pressure drops till it recovers and shifts, that is what I was chasing and fixed