CZ valvebody, no kickdown

[Thesjaak]

Hi all,

I bought a CZ and BR valvebody because the KC vakvebody I had kept annoying me.

I have the CZ in the car arm, as that should give me the best wot shift range according to the experts.
But, it doesn't kick down like I want it to, it seems like it hangs in 3rd and won't go to 2nd when I'm overtaking someone.
When I manually select 2nd it sometimes goes to 1st gear. Though, my shifter is an original 3 speed corvette shifter, so it might be that I'm not great at feeling which gear I select.

My pressures at idle:
P: 70 psi
R: 120 psi
N: 70 psi
D: 70 psi
3: 70 psi
2: 160 psi

Can't really select first as it's a stock corvette shifter.

Full TV in park is 125 psi, couldn't test D and R as I'm doing this alone.

I do have the transgo shift kit in there, I highlighted what I've installed.

Any ideas? It's great to have the 4th gear working finally, but it'd be nice to perfect these last issues/ flaws.

Many many thanks !

 

[Thesjaak]

Edit

 

[77 cruiser]

You should have over 200 psi @ full TV.

 

[Thesjaak]

You should have over 200 psi @ full TV.

Thank you!

Do you know where I should be looking next? Pressure relief spring and boost valves? It has the transgo white PR spring with transgo boost valves (all in the transgo kit)

You can see the needle fluctuating as well, maybe that tells something to someone.

In P: connected - disconnected - max TV @ 900 rpm

P R N D 3 2 with the TV cable connected @ 900 rpm

As always, very grateful for your insights

 

[TexasT]

Looks like you have a page similar to what I used to decide on hole sizes in the plate.

I have this transgo one too.
What mods did you do to the plate?


As the pressure is low, there could be a pump problem or a pressure relief prob letting the pressure off. I called this the bison mod but Mr Husek seemed to think he had a hand in it, so They both get credit. Below that roll in in the pump is a washer that gets added, then a spring and a ball bearing. The ball needs to be nice and not pitted and the seat it goes to also needs to be nice so the seal can keep the pressure in. Usually the pressure gets exhausted out the vent on top of the trans if it is bypassing so this may not be your problem. The washer also gives the relief valve a bit more seat pressure so you don't want a super thick one in there.


What did you install for a boost valve, rev/boost vale and spring?
Also lot of kits and advice includes a pin or rod to make the line bias valve non-functional. Did you do any thing to the line bias?

You may be the person I posted some things on facebook , in Bob K's 2004r group. You mention a corvette and I think that person did too.

Let us know. Lots of 2004r knowledge here.

 

[Thesjaak]

Looks like you have a page similar to what I used to decide on hole sizes in the plate.

I have this transgo one too.
What mods did you do to the plate?


As the pressure is low, there could be a pump problem or a pressure relief prob letting the pressure off. I called this the bison mod but Mr Husek seemed to think he had a hand in it, so They both get credit. Below that roll in in the pump is a washer that gets added, then a spring and a ball bearing. The ball needs to be nice and not pitted and the seat it goes to also needs to be nice so the seal can keep the pressure in. Usually the pressure gets exhausted out the vent on top of the trans if it is bypassing so this may not be your problem. The washer also gives the relief valve a bit more seat pressure so you don't want a super thick one in there.


What did you install for a boost valve, rev/boost vale and spring?
Also lot of kits and advice includes a pin or rod to make the line bias valve non-functional. Did you do any thing to the line bias?

You may be the person I posted some things on facebook , in Bob K's 2004r group. You mention a corvette and I think that person did too.

Let us know. Lots of 2004r knowledge here.

Hi,

In the plate I added the aluminium slug and drilled the holes in the middle of the range they advertise.
I have the transgo reverse/boost valves in there as well. I THINK transgo has a .472 valve as main boost valve?
I did all the work in 2021, we had a fire after and I forgot quite a few details after that tbf.
I do remember fitting a second slide spring, or a stronger one. Can't remember if I removed that rollpin and did something there though.

With the erratic movement of the gauge needle it might be a worn pressure regulator valve? I see sonnax sells oversized valves, but probably not possible to install them in situ?
I added the white transgo spring to the line bias.
I also added the spacer that goes inside the red spring inside the tv plunger. I wonder if this spacer can cause issues? If it kicks open other parts too quickly it might be the reason it doesn't downshift when overtaking someone?

I'd rather not pull the trans again atm, in the middle of moving houses and I don't have a lot of time. Though, I plan to marry in this car in 2024, so I want it to be perfect as well. I'm probably the person on facebook as well, I posted there too

 

[Thesjaak]

Update, had contact with Transgo, the boost valve is a .500" in their kit.
With the fluctuations of the needle I think it might be the pressure regulator valve behind it?
Or maybe it's just very very bad oil in there?
Getting tempted to just throw a wad of cash at the car and buy one of those A41 transmission packages...

 

[77 cruiser]

Have you tried running the rpm up to about 1500 to see if it's better?

 

[Thesjaak]

Have you tried running the rpm up to about 1500 to see if it's better?

I have not.
If it is better = bad pump? All parts are new (100 miles on it).
To be fair, I thought pressures were OK because I compared them with the stock pressures. And thought something obvious in the valvebody was wrong, like the spacer in the TV plunger.

Wonder if bad ATF could be the cause as well, couldn't get my hands on any name brand ATF when I filled it, so went with a quite unknown brand "viskoil".

 

[TexasT]

Doubt the fluid is the problem. Did you measure the clearance on the pump and rotor? New doesn't equal correct clearance.

 

[Thesjaak]

Doubt the fluid is the problem. Did you measure the clearance on the pump and rotor? New doesn't equal correct clearance.

Yeah, straight edge and feeler gauge. I think it was 3 thou but like I said, it was back in 2021 and I don't have anything on paper anymore

Though I try to think about what could the issue be in the valvebody, as I had good kickdowns with the KC valvebody but not with the CZ I just swapped in.
I swapped over most of the shiftkit except the red spring behind the TV plunger as the instructions said to leave the original.

Could also try a different gauge, I don't know how accurate 20$ gauges are. Could try and test the gauge with air pressure maybe.

 

[TexasT]

Seeing as it has sat, the vb could have some sticky parts in there. Not sure how many or if you even want one but a fluid bath and some exploratory removal and clean up of the vb and making sure of what you drilled and that the vb valves are all moving. I know I fooled with the tv valve on the bench some to make sure the valve moved and returned with the spring pressure.
Maybe with the tv cable disconnected and the rpm brought up to get the pump a pumping give that tv cable some sharp pulls to get the pressure to jump. Could possibly "flush" some stuff out and in lieu of a fluid bath easy to try.


I have a pan like this that I try to catch and reuse fluid when making the changes. A drain plug in the pan is also pretty handy.

 

[Thesjaak]

Seeing as it has sat, the vb could have some sticky parts in there. Not sure how many or if you even want one but a fluid bath and some exploratory removal and clean up of the vb and making sure of what you drilled and that the vb valves are all moving. I know I fooled with the tv valve on the bench some to make sure the valve moved and returned with the spring pressure.
Maybe with the tv cable disconnected and the rpm brought up to get the pump a pumping give that tv cable some sharp pulls to get the pressure to jump. Could possibly "flush" some stuff out and in lieu of a fluid bath easy to try.


I have a pan like this that I try to catch and reuse fluid when making the changes. A drain plug in the pan is also pretty handy.

See, I wonder about that too. I don't know how the transmission 'decides' it wants/needs to downshift.
I dont know which valve it is + if it downshifts at an absolute pressure like 150 psi, or if it downshifts when it senses an X psi difference in pressure. One of the guru's will be able to answer that
With atf being a good cleaning oil, I hope (hope) anything that's stuck will loosen over time. The car isn't at my garage atm as I'm moving houses, so won't be able to test anything else untill friday/saturday. But hope I can loosen things up by then.
The joy of doing your own car-work... if shipping wasn't so expensive I would've bought myself the A41 already, but 1.1k shipping +30% tax is a bit much

 

[Thesjaak]

https://youtu.be/IP0N5L5csTQ?feature=shared&t=960
Interestingly enough, in this video transgo mentions you need to remove the spring on the big weight whenyou have a performance VB like BRF or CZ.

 

[TurboBob]

See, I wonder about that too. I don't know how the transmission 'decides' it wants/needs to downshift.
I dont know which valve it is + if it downshifts at an absolute pressure like 150 psi, or if it downshifts when it senses an X psi difference in pressure. One of the guru's will be able to answer that
With atf being a good cleaning oil, I hope (hope) anything that's stuck will loosen over time. The car isn't at my garage atm as I'm moving houses, so won't be able to test anything else untill friday/saturday. But hope I can loosen things up by then.
The joy of doing your own car-work... if shipping wasn't so expensive I would've bought myself the A41 already, but 1.1k shipping +30% tax is a bit much

The TH2004r Principles of Operation book has a ton of very good info on these topics. The "kickdown" is different in different valve body types, I don't have the specifics, but if I remember, there is a hole in the TV sleeve that allows kickdown (detent) operation. So this may be related to your issue.

I agree that your pressures seem low. There may be an issue with the TV plunger, spring, and sleeve (its possible to get the roll pin in the wrong groove, I think). The TV limit and line bias valves all affect this, as well as the MTV up and MTV down stuff.

Basic shiftpoint control is from the TV pressure vs governor pressure, ignoring the MTV stuff (creates hysteresis), once governor pressure exceeds the TV pressure for a given shift, the shift happens. More TV (throttle) takes more governor pressure (higher speed).

There is a lot of additional detail in that P.O.O. book, You're chasing your tail asking questions on here until you can read thru all that info.

 

[Thesjaak]

The TH2004r Principles of Operation book has a ton of very good info on these topics. The "kickdown" is different in different valve body types, I don't have the specifics, but if I remember, there is a hole in the TV sleeve that allows kickdown (detent) operation. So this may be related to your issue.

I agree that your pressures seem low. There may be an issue with the TV plunger, spring, and sleeve (its possible to get the roll pin in the wrong groove, I think). The TV limit and line bias valves all affect this, as well as the MTV up and MTV down stuff.

Basic shiftpoint control is from the TV pressure vs governor pressure, ignoring the MTV stuff (creates hysteresis), once governor pressure exceeds the TV pressure for a given shift, the shift happens. More TV (throttle) takes more governor pressure (higher speed).

There is a lot of additional detail in that P.O.O. book, You're chasing your tail asking questions on here until you can read thru all that info.
View attachment 394939
View attachment 394940

Interesting. The book certainly would help me!
What I did notice on this VB is that the YV plunger sleeve came out quite easily. On my KC VB it is quite a tight fit. I can imagine it's leaking/bleeding pressure there.
Imma pull the pan again on saturday and have a look, I'll inspect the BR valvebody I have as well to see how things function there. Especially the TV plunger area.

 

[Thesjaak]

cup plug is missing. Im guessing thats the issue. Fitted the BRF and had a lot better pressure differential (70 idle at 600 rpm - 150 full TV at 600 rpm).
The brf does shift a tad on the high side at light throttle ( 2600 rpm 1-2) and 2-3 is a bit close as well. Might experiment putting the small spring in the big weight of the CZ governor.