This one's for Bruce, MTV up pressure too high...

[bry593]

Hi Bruce,

I think this will be an easy one. I recently installed an '87 CZ trans in a 2600 lb car. It works much better than my OG from a hot-rod perspective. It shifts hard and fast whether in Drive or manual. Additionally, the D5 converter really helps on the launch!

So, everything sounds great, well not everything. Under normal driving conditions (cruising), the trans will not upshift until 3000 rpm or so. This really hurts the mpg. I think I might know what the problem is, but I want your advice before I pull the pan.

I modified the trans with a 1/2" TV boost valve and Superior pressure regulator spring. I also added the Superior line bias spring and TV plunger spring. However, I did not install the Superior TV boost spring (didn't want to pull the Valve Body). By the way, these were the only components used from the Superior kit.

Here's what I think is happening. My MTV up pressures are too high at low throttle positions due to too much TV Feed. The TV feed is bleeding through because I installed the stiffer Superior plunger spring without installing the complemenatry TV boost spring. I would guess that the factory CZ boost spring is being overwhelmed by the Superior Plunger spring thereby opening the throttle valve and light throttle.

If my theory is correct, I should be able to reduce the MTV up pressures by replacing the plunger spring with the factory CZ spring?

What do you think? Am I on to something here or am I way off the mark?

Many thanks,
Bry593

 

[WE4]

Nope... you are fine I think. Yes change plunger spring which you do not have to pull vb for and try. What does pressure gauge tell you? Is it extremly high? TV and mainline are not the same. You didnt play with tv limit did you? That is the kiss of death.
What happens if you take tv out? Will it act more normal.? I would try that first. I will have my cell on and with me Sat. 916-952-9567 if you want to chat. BT

 

[bry593]

Nope, I didn't touch the TV limit. I only changed the line bias, plunger and mainline pressure spring.

I have a lot of tools, but I haven't invested in a trans gauge. I know its only a 300 psi gauge, 8' foot of trans line, and a 1/4 NPT male by 3/8 hose barb.....

When you say, take TV out, could I do this simply by removing the TV cable from the quadrajet carb temporarily ? So long as its just a slow trip around the block (to replicate cruising), it shouldn't cause any physical damage. Plus, this will take the throttle valve completely out of the picture.

I'm going to give this a try. I'll let you know what happens.

Bry

 

[77 cruiser]

I think what Bruce meant by taking TV out, was to back off a couple clicks on the cable adjustment.

Jim

 

[bry593]

Well hell, that didn't work... With the TV cable detached, it didn't want to shift at all. Doh!!! I forgot about the GM safety feature.... With the cable disconnected, the check ball seats and TV pressure is restored.....

Sounded like a good idea at the time. I guess I'll be pulling the pan now....

Bry

 

[bry593]

Jim, I think that is exactly what he meant.

I just adjusted the cable about 1/2 of its adjustment toward the carb, and it shifts smooth at low rpms.

Seems to point to the plunger spring.

Bry

 

[MeanBuicks]

Originally posted by bry593
I know its only a 300 psi gauge, 8' foot of trans line, and a 1/4 NPT male by 3/8 hose barb.....

That would be a 1/8 NPT male fitting, BTW.

 

[bry593]

I appreciate your help and advice Bruce and Jim.

Thanks for the correction on the fitting Greg. It's best to be accurate as possible in case someone references these posts for their own project.

Bry

 

[WE4]

Let me get this straight.... When you took some TV OUT it kinda was better? If that is true and 4th is late.... yes plunger spring would be my guess

 

[bry593]

Hah!!! It works mucho superbo....

Hi guys,

Thought I'd let you know the results of your advice.

I pulled the pan and reinstalled the factory CZ spring this morning. Yeah, I know it's been a week, but hell I gotta work during the week...

Anyway, after the spring replacement, I pulled the TV cable to max and backed it off about an 1/8". Net result, cruisin' shifts in the 1800 rpm range. Just how I like it.

Best of all, when I punch the pedal, the pressures come up and the trans will shift at 4500 in drive. Better yet, when I shift manually, I can take it to 5000 and that will chirp my tires in 1-3. I gotta get this thing to the track. In a car this light with a 350 Chevy, it screams! Matter of fact, this afternoon I smoked one of our GT friends using only an aluminum foot (as opposed to lead).

Now that my trans is working right, maybe I should concentrate on more power!

Again, many thanks!!!
Bry