Pressure Problem?

[turbojimmy]

Hi all,

I’m having a problem with my car that is causing shifting problems. I’m reluctant to say I’m having trouble with the transmission itself because I’ve had two different, freshly rebuilt transmissions in the car and they both behave the same way.

I think it’s a pressure problem. Adjusting the TV cable has no affect on the problem. Here’s what it does:

Under ‘normal’ acceleration, it will shift 1, 2, 3 and 4 without any problem. 1-2 is hard, 2-3 is a little softer and the shift to 4 is barely perceptible. Shift points (RPMs) seem okay. TC locks up very firmly.

Under moderate acceleration, however, the 2-3 gets really sloppy. The harder the acceleration, the worse it is. I can feel it drop out of 2nd at which point acceleration slows dramatically as RPMs increase. At moderate throttle it will eventually (after about a full 1-2 second delay) shift to 3rd and sort of stay there. It will drop out of third if I give it enough throttle but never quite go back down to 2nd – it just slips.

Under WOT the car shoots right to redline when it tries to shift to 3rd. If I let up on the throttle it will shift.

When driving along, when I feel it drop out of 2nd getting ready to go to 3rd, if I give it some throttle I can make it ‘stick’ in between 2 and 3. It doesn’t drop back to 2 nor does it go up to 3.

This is the 2nd transmission from the rebuilder that does this so I’m 99.9999% sure that it’s not the transmission itself. I have had transmissions from him that work great and I have 100% confidence in the rebuilder. So, I don’t want to bring the car back to him unless I’ve exhausted all possibilities external to the trans itself.

Assuming the above sounds like a pressure problem and it’s being caused by an external problem, what are the possibilities? I bypassed the cooler in the radiator, leaving only my external cooler in place, and it does the same thing. Could there be a line pinched somewhere? Could it be the torque converter (I just had Precision go through it a few months ago and it checked out fine)?

Any other ideas?

TIA,
Jim

 

[mikestertwo]

The problem is internal to the trans. Other than the T.V. cable ajustment all pressures are controlled internally by the pressure regulator valve, boost valves, and line bias valve.

 

[Lee Thompson]

I'll loan you a 6 shooter

And shoot it !!!!
Sorry to say but IMO it is internal. I could loan you a gage with hose and fitting for a pressure reading, and I bet it drops off with more throttle.

 

[turbojimmy]

And shoot it !!!!
Sorry to say but IMO it is internal. I could loan you a gage with hose and fitting for a pressure reading, and I bet it drops off with more throttle.

Thanks. I bought a gauge to check it out - it should be here any day now. I was hoping for something external - an easy fix. Wishful thinking I guess....

Jim

 

[chris718]

does the car make a wot 2/3 shift without lifting the gas?

 

[turbojimmy]

does the car make a wot 2/3 shift without lifting the gas?

No, it won't make a 2/3 shift without lifting the gas. BUT, it's not like it's 'stuck' in 2nd gear. I can feel it come out of 2nd and then the motor redlines. So it's trying to shift but it just slips. It's all about how much throttle I give it. Light throttle = nice shifts. Medium throttle = long, sloppy 2-3. Hard throttle = no 2-3.

I've pulled the TV cable as tight as it would go (adjust it back as far as it would go toward the firewall) and it doesn't solve the problem. All that does for me is make for early shifts and then it doesn't want to downshift. Obviously going the other way with the cable is worse.

Thanks,
Jim

 

[mikestertwo]

.
I've pulled the TV cable as tight as it would go (adjust it back as far as it would go toward the firewall) and it doesn't solve the problem. All that does for me is make for early shifts and then it doesn't want to downshift. Obviously going the other way with the cable is worse.
Thanks,
Jim

That should make it shift later and more firm

 

[brian]

Did it do these things from the start, right after the install? Has it gotten worse since fresh? Significnatly worse?

This question will sound stupid to some.....But...
What upper plenum, throttle body combo are you using?
70 mm? Precision upper, spacer?

 

[turbojimmy]

What upper plenum, throttle body combo are you using?
70 mm? Precision upper, spacer?

I have a stock TB with a Precision doghouse and RJC spacer. It all worked fine before a recent lock-up problem. My Vigilante TC stopped locking up for some reason. I sent the trans to the trans guy and the converter to the converter guy. Got both back and put them in. No 3rd gear. Swapped the trans, still no 3rd gear.

That should make it shift later and more firm

I'd have to try it again to be sure, but I thought it was shifting earlier (but firmer) but then it didn't want to downshift. With that cable tight, when I roll up to a light it takes a long time to drop to 1st (it actually bogs a little). I may have it backwards in my head tho. Long story short is that adjusting the TV cable does nothing to address the 2-3 shift slippage.

Thanks,
Jim

 

[turbojimmy]

Okay - I have some data.

First, I was wrong about the TV having no impact on the problem. If I extend the TV cable the whole way to the end of its travel toward the firewall (as tight as it will go) it will still slip in 3rd, but it takes a lot more power to do it.

But, here are some data points. The cable does not adjust itself due to the geometry of the Precision housing and RJC plate. I have it adjusted as tight as it will go before it limits throttle travel. Here's where it sits:

At this setting, pressures are:
Park: 50 PSI
R: 130 PSI
4th: 50 PSI
3rd: 50 PSI
2nd: 160 PSI
1st: 160 PSI

It slips pretty bad this way. Pressure never goes above 150-160 PSI at any RPM with the gear selector in OD.

I picked a random, tighter setting and it does improve the situation but the shift points are way too late and the TV cable restricts throttle movement (I can only get 4.0V out of the TPS). Also, at WOT (which, again, is 4.0V) it oscillates between 2nd and 3rd). It does take a lot of power (WOT) to get it to slip. Here's where the cable is set:

Pressures at that setting are:
Park: 100 PSI
R: 190 PSI
4th: 100 PSI
3rd: 100 PSI
2nd: 160 PSI
1st: 160 PSI

Set this way, it will still slip but only at a speed where it drops to 2nd and then has to come back up to 3rd. On the highway it did not slip at WOT until I slowed down to 40MPH or so and let it drop to 2nd. Here's a graph of said slippage:

http://www.turbojimmy.com/slippage_032108.htm

Last, I checked the pressure at idle by detaching the TV cable and pulling it all the way out. Pressures are:

Park: 180 PSI
R: 260 PSI
D: 180 PSI
3: 180 PSI
2: 160 PSI
1: 160 PSI

Does any of this tell you anything??????

Thanks,
Jim

 

[turbojimmy]

Ok, I have more 'dater'.....

My brother's car, which shifts very nicely and does not slip and was built by the same guy has the following pressures:

At idle, with the TV cable set as pictured (stock doghouse, RJC spacer):

Park: 80 PSI
R: 120 PSI
OD: 80 PSI
3: 80 PSI
2: 210 PSI
1: 210 PSI

With the TV cable pulled all the way out:
P: 240 PSI
R: 210 PSI
OD: 220-240 PSI
3: 220-240 PSI
2: 200 PSI
1: 180-200 PSI

So he has a lot more pressure than I do at the same TV settings. I bypassed my aftermarket cooler and drove it with the just the radiator cooler. Didn't help.

Jim

 

[chris718]

measure how much the string part of the cable is pulling out between both cars.it may be the cable is binding in the housing.pressures are low at wot.

 

[turbojimmy]

measure how much the string part of the cable is pulling out between both cars.it may be the cable is binding in the housing.pressures are low at wot.

Chris - I'll do that. I have an extra cable (new TCI adjustable) here that I can try, too. The cable that's in it is the one you sent me long ago and it might be messed up by now.

Thanks,
Jim

 

[turbojimmy]

I checked the travel on both cars. Both are ~5" to the end of the cable (measured from face of the bracket) when fully extended.

Jim

 

[chris718]

Jim one thing i always do is take care of my customers.Bring me the car and iI will get it right for you.It may take a few days as i am really busy but we can fix it.My original repair was on a dynotech built 2004r that was bbqd.although i charged you for a repair and not a full build ill fix it for you.

 

[turbojimmy]

Jim one thing i always do is take care of my customers.Bring me the car and iI will get it right for you.It may take a few days as i am really busy but we can fix it.My original repair was on a dynotech built 2004r that was bbqd.although i charged you for a repair and not a full build ill fix it for you.

Chris - whenever you have the time I'll bring it by. You've been very patient and generous with me over the many years I've been having troubles with my trans. The purpose of this thread was to get some opinions as to what the problem might be before I troubled you again with this thing. So far, none of the problems I've had have been related to your work but you've taken the time to fix them anyway. It's just been one freakish problem after another.

E-mail me when you have time and we'll work something out. You've always been fair and I know you will be this time too.

Thanks,
Jim

 

[chris718]

bring me the car this week.just call in and tell me when your coming.

 

[TurboBrett]

Thanks. I bought a gauge to check it out - it should be here any day now. I was hoping for something external - an easy fix. Wishful thinking I guess....

Jim

Jim,

If you don't mind my asking, which gauge did you buy?
I'm having what some believe is a pressure problem myself and need to test it out.
I haven't seen any of our vendors selling them, but I see some on ebay in the $40 range, not sure of quality though...

Thanks for any help you can provide.
-Brett

 

[turbojimmy]

Jim,

If you don't mind my asking, which gauge did you buy?
I'm having what some believe is a pressure problem myself and need to test it out.
I haven't seen any of our vendors selling them, but I see some on ebay in the $40 range, not sure of quality though...

Thanks for any help you can provide.
-Brett

I got one from SJ Discount Tools (sjdiscounttools.com) for either $34.95 or $39.95 (don't remember which). I don't know why, but the same one is now $46.39 on their site. I know I didn't pay that much for it. It came with two gauges: 0-600 PSI and a 0-150 PSI (I think). I used the bigger one (0-600) PSI. It came in a plastic case with a 6-foot hose (which is just about long enough to come out under the car and to duct tape the gauge to the windshield). It also came with an assortment of brass stuff to hook it up. I used an elbow and a 2" long pipe from the kit to connect the gauge to the test port on the trans. It's one of those things that you use infrequently but when you do need it it's nice to have your own.

HTH,
Jim