High Line Pressure (No change with TV cable), D4 Engine Loading

[Darrell1987SS]

I'm having some issues with a newly rebuilt 200-4r.

It's an 87 CZF from a Monte SS with the BRF valve body. During the rebuild, a "Superior 200-4r HP" kit was installed. Currently it is installed in the frame (no body) so I can't apply brakes or do any loaded runs, so all pressure testing is with the wheels in the air.

The bad signs that something is not right are:

1. The line pressures are around 225 in all ranges including park and neutral and are not effected by the TV cable position at all.

2. When D4 is selected, the engine seems to load down at idle, but some additional throttle will spin the tail shaft (this doesn't happen in R,N,D1,D2,D3 although in D3 I though I heard some type of "chatter" at one point.

3. No shifts seem to happen in D2, or D3, (haven't reved the engine in D4 becuase of the loading issue #2) but I haven't pushed above 2,500 3000 RPMs since the engine was just broken in and I didn't expect much with the high line pressure.

Reverse and neutral seem OK as far as direction of motion or no motion. D1 and D2 give forwared motion, although I can't exactly tell what gear it is in (I don't have the speedo hooked up), but by eye I would say it's one of the lower gears.

Things I've tried:
1. Removed TV plunger and checked for free movement of TV valve (seems like roll pin is in the correct valve "slot"). Motion of plunger seems fine with cable action.

2. During the rebuild, I left the exhuast checkball in place (maybe not the best thing). From what I can tell by pushing a small wire into the hole, it is free. The pin for the TV cable failure safty seem to move into the VB correctly so that the checkball would be unseated when the TV lever touches the plunger.

3. I pulled the regulator/rev/boost value out of the pump to check for binding or improper intallation, but that seems fine.

I'v read that a stuck slider guide can also cause pressure issues, the pump was converted from a 7 vane to 10 vane setup with new rotor and vanes, but the origial pump housing and slider guide was reused. The rotor was compared to the original with a micrometer for proper clearance.

I'm not sure if high line pressures should cause my D4 issue, so I'm open to the idea of multiiple issues.

I'm looking for anything else to check before or after I pull the tranny.

Any thoughs or ideas would be greatly appreciated.

 

[bison]

All i can think of if you verified the pressure reg setup is installed correctly is that The TV limit circuit is blocked and not allowing the circuit to supply the 90 psi its supposed to. Its worth pulling the pump to take a look. Maybe wrong pr valve with wrong pump casting?

 

[Darrell1987SS]

Thanks for your thoughts.

The pump housing and pressure regulator pair was reused from the original transmission which had been working in general (shifts were ok as stock but the TCC had been disabled since it tended leave the TC stuck locked), so I don't think there should be a mis-match.

When I had the pan off I did push on the end of the TV limit valve which is exposed in the VB and it at least moved freely (doesn't mean something is not clogging that circuit though). Would a problem with the 90 PSI limit cause the D4 engine loading issue also?

Is it possible to remove the inner piston part of the boost valve in the pump to force a non-boost condition and see if the pump is cabable of non-boost pressures for testing? Maybe I can learn more before pulling the tranny.

 

[Darrell1987SS]

I decided to remove the rev boost valve and boost valve, leaving the valve sleeves in place. The result is that the line pressure dropped to about 60-70 psi cold, so I think this means the pump and regulator are working and that the problem is that either the boost or rev boost signal at the regulator is always present and independent of TV position.

Also, the D4 engine loading issue doesn't seem to happen with the boost/rev boost vlaves removed, but I was unable to get any noticeable upshifts (wheels in the air) and the wheels seemed slow for the RPMs so I think 1st or 2nd.

My plan is to drop the pan and remove the TV Limit for inspection. I'm still waiting for my copy of GM's 200-4r fundementals, so I don't exactly understand if a malfunction in the "TV limit valve" would also cause unshift issues even with the boost valves removed. Any info would be great.

The shift kit also changed the "line bias" spring, how would that effect things if it were incorrect?

 

[Darrell1987SS]

I just compared the Line Bias Spring that was installed from the superior 200-4r HP kit and it seems very different than the original one:

Original Spring: .275" OD, 1.4" Long
Superior 200-4r HP Kit (green spring): 0.231" OD, 1.1" Long (much stiffer)

I read another post refering to an INNER spring from a superior kit, but my install instructions say to replace it, not make it an inner spring of the existing, so what is correct?

Would the shorter spring alone give me no TV response and high pressure all the time?

 

[Darrell1987SS]

After removing the VB and checking every valve, sleeve and spring, nothing looked bound or improperly located. I was suspicious of the "Line Bias Valve" so I went back with the original one and also removed the TV exhaust check ball. After it was back together, the line pressure started reponding to the TV cable, not sure exactly what fixed it though.

However, there is still an issue which is most noticeable in D1 (when I originally posted I had confused myself into thinking I was in D4 since I'm shifting with the lever on the side of the tranny).

The pressures now are:

No TV, Full TV
P: 80, 200
R: 160, 250
N: 90, 200
D4: 90, 190
D3: 90, 190
D2: 165, 165
D1: 190, 150

The D2 Numbers and D1 with Full TV seem wrong, but I'm not sure what the cause would be?

In D1 with the wheels off the ground, the engine loads down and the output shaft stops with Full TV and I hear some clicking from the forward area of the trans.

Reverse rotation is fine and in D4 I can get an upshift that applies the 4th clutch based on the pressure tap. Pulling the TV cable with the 4th clutch will cause it to disengage (again based on the tap), but I hear some clicking with the TV pulled.

Could this be caused by an incorrect Servo Pin length?

Any other thoughts on what to check would be greatly appreciated.

 

[bison]

Now your not getting any boost in M1 and M2

 

[Darrell1987SS]

I agree, that the pressure shouldn't drop in D1 with FULL TV, I need to make sure this isn't due to the drop in RPM when the engine loads down because of the tranny problem. I would also think D2 should be 190, 190 based on the others (again maybe rpms were too low, will test again).

What I'm confused about is whether there should be any boost in the M1 (D1), M2 (D2) ranges. The ASNG manual I have doesn't indicates that there shouldn't be any change in line pressure for these ranges for the stock trans, but some of the posts I have read also seem to find problems in others pressure readings when there is no change.

So what's the right behavior in D1 and D2?

Is a TV dependent line pressure (i.e., change with cable position) in D1 and D2 based on having installed a larger (or different) boost boost valve or Rev boost valve?

Thanks for anyone who can help clarify.

I think I'm going to try the original boost valve and sleeve. From the diagrams I now have from the GM priciples book, it looks like it might be possible for the D2 boost signal to bleed back into the REV boost signal at the regulator boost/rev boost valves if something was wrong (might change with TV also). This bleed back into the REV signal should be exhausted at the manual valve, but maybe there would be enough pressure to fire the direct clutch. Looks like pan drop #7...

 

[Darrell1987SS]

Thanks for you comments bison, it made me did deeper into why the pressure numbers were like they were in my manual. Hopefully, I'm coming to some correct conclusions though...

After some thought about what is shown in the GM principles book, I don't believe the main boost valve will have any effect in the manual D1 and D2 ranges. The reason is that in D1 or D2 the regulator is fed with the "Drive 2" Signal at line pressure, which acts on the top of the boost valve, pushing against the force at the bottom from the "Modulated TV" signal (max 90 psi when working < Line). So the "Drive 2" force always wins and keeps it closed. So the only thing that can change the D1 and D2 line pressures are a different regulator spring and/or a different Low/Rev Boost valve/sleeve.

Looking at my pressure numbers for D2, with this in mind, might make sense now. Since I'm only have a new regulator spring and main boost valve, I would see an increase in D1, D2 line pressure over stock, because of the stiffer spring. The pressures would still be lower than the Boosted values in the D3 and D4 range, because I didn't upgrade to a larger low/rev valve.

If my thinking is correct then the 165 pressures in D2 are fine (or at least expected) and the real problem is in D1. If my understanding is correct, it seems like there should be more talk about the low/rev boost valve, but I kinda feel like the focus (of what I remember reading) is mostly on the main boost, when I would think most would manually shift (could be wrong on that) under the harsh WOT conditions and want boosted D1 and D2 line pressures.

So it seems the the D1 pressures are the most strange. I think the only way to have the 190 psi which matches my boosted D3 and D4 numbers would be if the Main Boost valve fires when the manually valve opens the "Lo" Feed. I think this could only happen in one of two ways:

1. The "Modulated" TV signal reaching the regulator would come up to line pressure to fight the "D2" regulator signal.

2. The "D2" regulator Signal would be removed in shifting from D2 to D1.

I think 2 is unlikely because it would also require full modulated TV at the regulator to show the 190 PSI and doesn't explain my engine loading issue. So I guess I need to come up with a likely place to look for the #1 problem. With the moduled TV at line pressure, opening the TV Plunger would bring the the "DET" signal and "P.T." (part throttle) signal to Line pressure so I still need to explain why that would engage the clutches in a way that causes the engine to load in D1.

Any easy place to tap the TV Pressure?

 

[bison]

I assumed you had a .296 rev boost valve and sleeve. Is this accurate?

 

[bison]

The pump housing could be cracked or have cross leaks that are applying the TCC circuit which would load the engine down also.

 

[Darrell1987SS]

I'm not sure of the rev boost size (it's stock monte SS), but I will measure it next time it's out, I'm sure it will happen soon.

Will the .296 Rev Valve give boost to about the 200 psi mark so things are essentially equal between WOT D3,D4 and manual D1, D2, any preffered source/brand?

Maybe I misunderstood, Bsion, Did you mean by "Now your not getting any boost in M1 and M2" that I wasn't getting boost relative to the other ranges (i.e. R, D4 (full TV)) or did you mean relative to No/Full TV?

"The pump housing could be cracked or have cross leaks that are applying the TCC circuit which would load the engine down also."

Not a bad thought, I should explain that the wheels are in the air, and the drive shaft stops when I pull the TV full in D1, while the engine loads down. So I think the loading is internal to the tranmission. I think if the TC was engaged with no output shaft load (wheels in air) and no outputshaft (driveshaft) motion, the engine would need to stall (unless more problems lurk inside). In order to get the driveshaft to move, I need to start reving on the engine and it feels like the reving up to the stall point (no lockup) that you might get while power-braking (but my wheels are currently in the air).

Its what I might expect if the 4th clutch and over drive overun clutch were engaged at the same time. But I have a gauge on the 4th clutch port and can see it shift into 4th when in D4 (visually looks like a shift takes place on the driveshaft). When the loading takes place, no 4th clutch port pressure is seen and the overdrive overrun clutch would have been locked in D3 and D2 also (no loading observed in these gears). May one of the other clutches or band, still reading my way through the gear section of the GM fundementals book.

I do appreciate the comments, hopefully before I start tearing it apart, I'll have at least a handful of suspect areas to look at.

Maybe I'll try taking out the band apply pin to see if the loading effect changes, since I can do this without pulling the tranny yet?

 

[Darrell1987SS]

I think I finally got somewhere, I removed the servo pin and pistons to see if my D1 Full TV loading would disappear and it did. Then I started looking more closely at the pin adjustment and it was way way too tight, band was essentially applied from the cover pressure. Back in march when I did the rebuild, I didn't have the measurement tool shown in the ATNG manual and my haynes GM automatic trans overhaul manual mentioned nothing of the adjustment (I probably should have had the CK manual, but I don't think I knew about it at the time, though two sources were enough). I saw the cover retaining tool in the ATNG manual and figured it takes some pressure to get the cover O-ring over the retainer groove and went on my merry way with the rest of assembly.

After reading so many of the posts here I immediatly realized when I couldn't turn the output shaft in both directions that I had found my loading issue. A little quick grinding of the pin and the 0.1 inch travel from applied to retainer rest was there. I think it's a good point to make (obvious after doing it) is that the servo cover O-Ring needs to be removed when using this method for adjustment and that it takes some force to convince the O-ring to Jump the retainer groove after you have the correct pin length.

At first there was still some odd behavior, but I think since the the band was keeping the drum form turning and the servo was forced in, it was keeping trans fluid from purging out all the air in the system. After running through the gears and pulling the TV cable, it sucked up another 3/4 quart of fluid and started to bevhave correctly (at least with the wheels off the ground).

I'll recheck the pressures tommarow and see if they seem right now.

 

[SSedan64]

Glad you found the bind Darrel. Hope the pressure check out good. I've been following this thread hoping it would be something simple.
Todd

 

[Darrell1987SS]

I put the bias spring from the superior HP kit back in since I didn't think it had anything to do with my original trans issues. But I think things look good so far, seems to shift through all gears and pressures are:

P - 90/220
R - 150/250
D4 - 90/220
D3- 90/220
D2 - 190/190
D1 - 190/190

4th clutch pressure port goes to about 100psi when it shifts into 4th.

probably could have put in a larger reverse valve so the D1/D2 pressure were higher. So at least until the car sees some pavement, I'll call it good.

 

[bison]

probably could have put in a larger reverse valve so the D1/D2 pressure were higher. So at least until the car sees some pavement, I'll call it good.

What size was it?