Attn A413 experts! Need help! What's going on? datalogs inside...

[ShelGame]

OK, so, my car is not running what it really should be running. I've noticed something in my datalogs that I don't understand. At first, I just thought it was wheelspin, but it's there in the same place in every single run. And, it's not where you'd normally think of getting wheelspin. My speed goes flat at ~22mph for 1-1.5 sec just before I shift from 1-2. The trans does flare a bit after the 1-2 shift. Also, my shift light is set to 5100rpm, but the data shows the RPM going up to 5500-5600 rpm in 1st - which is WAY too high.

I'm wondering if the trans is slipping at the top of 1st. What would cause that?

My trans was rebuilt by a friend who works for Mopar. He's a trans engineer and knows what he's doing (he builds Viper trans for road racing). But, he bought the RMVB from Turbo Action, and I don't think he did anything to it before he bolted it in (I need to ask). I've read that they are set too low from TA and need to have the line pressure increased. Would that help this issue?

What else? The trans has >20 passes on it since I installed it last year. But, track only. No street time.

Here's a screenshot of one of my data logs. All of my data logs show this flat spot on the speed trace at ~22mph. Some smaller than this, but they all show it. In this one, it looks like the RPM's jump when the speed flattens out.

[Speedeuphoria]

yeah try to up the line pressure if it is not allready, you can check it in 2nd gear in the(crap forgot the port name, its near the top oil cooler line, not right next to it but one over). It will jump 20psi or sowhen you rev it up to 1600or so. Dont do it from a stand still, jack the car up put in 2nd and check. You can max it out on that VB as it only goes a little over 100psi or so(clockwise lowers,ccw raises pressure)

Also the band may need adjustment on top of the case(kickdown band, used when going to 2nd), maybe turn it in a 1/2 turn and see if it helps.

[turbovanman²]

The port name is Kickdown apply, its the first one looking it the front of the trans, middle row. It should be around 130 psi.

I would say its slipping at the top end, maybe due to low line pressure or loose clutch packs. I know Chrysler techs know there stuff for stock but alot know nothing of hipo so he could have set them loose, as per OE specs.

[ShelGame]

OK, assuming I measure the line pressure low - how do I adjust it?

[Stevien1]

OK, assuming I measure the line pressure low - how do I adjust it?

Drop the trans pan and you'll see the regulator screw on the valve body (driver side front). It's an allen, 6mm IIRC. Turn it counter-clockwise to increase pressure, but keep an eye on the threaded spring seat. If you turn it too much, the seat will thread right off the screw (after about 7 turns from stock).

If your trans guy drilled the side of the case and put a plug in it, you can avoid dropping the pan.

[87csx2.4]

If its a turboaction vb and he didnt adjust line pressure its definately low they send them with very low line pressure for some reason.Everyone Ive ever installed I max them out and it will get about 120 to 130 psi.

[87csx2.4]

I agree with simon,in 1st gear the only thing engaged is the rear clutches and the overunning clutch should be locked.If the overunning clutch is not holding it could cause the same feeling as a slipping clutch pak.By the looks of your logs I would say when you've got a loose clutch pak though because it flaten's right when the boost peaks.Put your pressure gauge in the kickdown release port and put the car in 3rd gear and see what pressure you get,this test the front and rear paks.It should be the same as the kickdown apply if not one of the paks are leaking.With the turboaction vb this is the only way to test the rear pak.

[ShelGame]

That's exactly what my trans builder just told me - test the line pressure. He also suggested I check and adjust the front band. It was new when he installed it and he said the friction material can bed in and the band can stretch a little.

But, I'm showing slippage well before I shift. So, I think it's probably line pressure. He definitely did not check/adjust it. He only assembled the trans - I installed it. He had no way of measuring it before I got it in the car. I'm betting that's the problem. I had heard that about the TA RMVB also.

It's due for a fluid/filter change anyway. Anything special I need to measure the line pressure? I have 3-4 air pressure guages, will that work? Or is there a special trans pressure guage I need to get?

[turbovanman²]

That's exactly what my trans builder just told me - test the line pressure. He also suggested I check and adjust the front band. It was new when he installed it and he said the friction material can bed in and the band can stretch a little.

But, I'm showing slippage well before I shift. So, I think it's probably line pressure. He definitely did not check/adjust it. He only assembled the trans - I installed it. He had no way of measuring it before I got it in the car. I'm betting that's the problem. I had heard that about the TA RMVB also.

It's due for a fluid/filter change anyway. Anything special I need to measure the line pressure? I have 3-4 air pressure guages, will that work? Or is there a special trans pressure guage I need to get?

You should use a guage that can measure up to 1000 psi. The tranny pump is easily capable of that and in reverse can spike to at least 400 psi.

I really like the reusable pan gasket, its saved me alot of money and time, lol! I also add a drain plug so its less messy. You can also add the line pressure plug if you want, with the pan down, you can drill the case and tap it for a 1/8 pipe plug.

[TurboJerry]

I've never seen a stock pressure reg. spring go any more then 90 psi maxed out. It sounds like the belville spring might be broken and not holding the clutches properly. It would usually chatter if the sprag is not holding properly. The band adjustment should be 1 to 1 1/2 turns. Any looser and the servo will bottom out. I also bypass reverse boost because of a broken case when running 135 psi forward pressure. (was 500 psi in reverse)

[Speedeuphoria]

I got a gauge from here
http://www.sjdiscounttools.com/atd-5550.html
thing is its got 1/8th NPT and the trans ports are all 1/16th NPT, which no one makes that size adapter AFAIK, so I had to use compression fitting into the trans then a small section of steel line for the compression fitting to another compression fitting to the hose/gauge.
it ships in less than a week

Your not going to see more than 100-130 in forward so it will work, reverse will pegg the gauge.

[ShelGame]

OK, next question - Assuming the line pressure is too low, and since I have 30+ passes on this trans - are my clutches now f'd? Or will they be OK after I turn up the pressure?

[Speedeuphoria]

hard to say, has it been acting like that the whole time?

[glhs875]

With a TA RMVB the only things holding 1st gear are the rear clutches and overrunning clutch (does not spin), with the latter not normally being a problem. And then for 2nd gear the kickdown band is applied and the overrunning clutch then spins. Unless I'm wrong about the overrunning clutch spinning in 2nd? But anyway, raising line pressure could help as well as possibly adding more clutches to the rear drum and/or reducing clutch pack clearance in the drum. The rear clutches are used for all forward gears. So if clearances are set too tight, the only gear in which a problem would occur from not enough clearance on the rear clutches would be reverse. I've still have a ways to go on these trans. as well, but I'm getting there. From the last round with Kevin Davis' car I learned alot more!!!

[ShelGame]

hard to say, has it been acting like that the whole time?

Pretty much it looks like. Though, it is noticeably worsening. My oldest datalogs show ~ 0.75 sec flat spot at 22mph, now it's up to 1-1.25 sec.

Actually, looking at the data some more, I really think fixing this will give me ~0.5 sec better ET at least. Not only is there a flat spot, but the acceleration from 0-60' is not what it should be. Some of that is wheelspin off the line, but the slope of the MPH line is smaller in 1st than in 2nd - that shouldn't be.

EDIT: OK, this has me really stumped - why does this happen at the exact same speed (~22mph) in every single datalog? Is there something in the trans that would cause the line pressure to be speed dependant? If it was simply slipping clutches, you would expect to see some variation in when/where it slips, wouldn't you?

[glhs875]

You'd think. But I do know that in the forward gears that line pressure rises some with rpms. Maybe at that mph is when the torque converter tightens up/ becomes more efficient and puts more stress on the clutches. I'm just throwing out some ideas. Or maybe there is an issue with the torque converter. Do your rpms raise or drop at the slope?

[glhs875]

Okay, I re-read your 1st post. The R's go up during the slope.

[ShelGame]

Okay, I re-read your 1st post. The R's go up during the slope.

You mean during the flatspot? Yes, R's continue to rise, but the slope stays basically the same even though the speed goes flat.

Here's another thing I thought of - I changed gear ratios from last season to this season (I changed the x-fer gears from 1.06 to 1.22). You'd think that would have an effect on the speed, wouldn't you? But no, it still slips at 22mph.

Maybe it's like "Back to the Future" - when that baby hits 22mph, look out!

[Speedeuphoria]

the line pressure dosent raise much after ~2000rpms or any. I was going to say its when your tires get traction or where the motor has more torque. Now that you say its the same w/ different gearing(which means different rpms) not sure.

I personally would drop the pan, adjust the line pressure to the max, tighten the rear band 1/2-1 turns(or torque to spec and back off 2-2.5 turns, instead of the 3.5 turns) Slap it back together and tighten the kickdown band a 1/2-1turn and try it, if it still slips then could be the converter or the clutches are bad or the clearence is too much

[XR Tuner]

You can get the adaptor at Jegs. Part #105-3280 1/16 to 1/8 npt adaptor.