Low pressure diagnostic help needed

[bnewsom]

I got a Mega Monster 2004R transmission from a friend that took it out of his GN before selling it. Supposedly a low mileage unit that was working well when removed. It sat up with all openings well sealed for about 3 years.
But he did say his son had taken the pan off and messed with it but was not sure what if anything was done to it. Looks like the pump may heave been taken off but not sure. He did not make any promises about it and cautioned me to check it out good.

Before it was installed, I pulled the pan and everything was clean on the inside and looked right so I just put a new filter and pan gasket on it and installed it with stock converter. I got the truck back on the ground, added fluid and went through the gear positions to get the fluid where it needs to be. You could tell it was going into forward and reverse when selected but I could tell it was slipping. I never did try to drive it.

I put the gauge on it and am barely getting 20 psi at idle in any gear position. I pulled the pan and made sure the pump regulator valve, spring and boost valve were correctly positioned and free. It all dropped out when I pulled the snap ring so could not see how it was installed. Put it all back in and tried it again. Pressure is still low. I kept it on the stands and got rpms up to about 2000. Pressure did rise to about 50. Did not change in L1 or any other position. One odd thing i noticed is when the TV cable was pulled about half travel, the pressure would drop to about 35. It did seem to change gears when in drive and idled up to 2000 rpm's.

Can anybody think of anything that would cause the low pressure besides the pump being toast? All ideas appreciated.

 

[SSedan64]

Figure 2 here shows the Pressure Regulator & Boost valve arrangement.
http://www.sonnax.com/system/instructions/700R4-LB1-IN.pdf

Did the old Filter neck Seal come out when you installed the new Filter?
Any Pump Noise?
Torque Converter installed correctly? Turbine, Stator & Pump splines engaged.

 

[bnewsom]

Figure 2 here shows the Pressure Regulator & Boost valve arrangement.
http://www.sonnax.com/system/instructions/700R4-LB1-IN.pdf

Did the old Filter neck Seal come out when you installed the new Filter?
Any Pump Noise?
Torque Converter installed correctly? Turbine, Stator & Pump splines engaged.

I did put the boost valves and pressure regulator valve back as in the illustration. I did notice on the valve where the arrow on the illustration is pointing had that land ground down some. I think I've seen this mod in a Gil Younger kit - any ideas on this?????

The seal was pulled out of the bore and the new seal was put on the filter neck and slipped into place . No noise coming from the pump nor any other unusual sounds.Best I could tell th TC is in correctly - slid it on, supported the weight while rotating it until it engaged the pump. There was about 1/4" movement of the TC between the trans and the flexplate before installing the bolts.

I did recall when I first tried started the engine and was moving the shifter, it did go into drive once firm enough to stall the engine. Other than that all indications have been low pressure.

Could anything in the VB allow pressure to bleed of like this possibly following the 3 years since it has been in operation.

 

[SSedan64]

More than 1/4" TC to Flexplate clearance requires Spacers. Normal clearance is 1/8" to 3/16"
I've read about some TCs' having poor/short Pump lug engagement.
It would have to be a major VB leak for Pr. to be that low.

 

[bnewsom]

More than 1/4" TC to Flexplate clearance requires Spacers. Normal clearance is 1/8" to 3/16"
I've read about some TCs' having poor/short Pump lug engagement.
It would have to be a major VB leak for Pr. to be that low.

So I guess assuming I have engagement of the TC to the pump, I must have pump issues? Anything else to check before dropping the transmission out?
Thanks,
Bob

 

[bnewsom]

Not sure from lack of responses if my problem is so basis that it doesn't deserve a response or what. This board does get a lot of respect and acknowledgement for being the best source on the 200-4R so opinions and ideas are welcome and appreciated. I'm decent at just about everything mechanical but automatic transmissions are far from being my strength.

With that said, I am going to pull it back out and go through the pump and valvebody. I'm guessing having low pressure in a transmission that was working well the last time it was in a car would have to have a problem in one of there areas? Anything else that can cause a sudden loss of pressure?

Also does anyone have any experience with Monster Transmissions. Since they did the original build, I was thinking about sending it back to them to go through assuming I can't sort it out. Warranty would obviously not be an option.

Thought I would include a picture of the engine/tans before it initially went into my 49 Chevy truck. Engine is a mildly built Cadillac 500, estimated 350 HP and 500 FT/LBS.

 

[SSedan64]

My best guess is there's a problem with the Pump.
Maybe one of the Builders will chime in.

 

[bnewsom]

Thanks for the replies. I'm wondering if there is something after the pump that could not be working correctly that will bleed off pressure that I should look for while I'm in there. Hopefully when I go into it there will be something obvious. I'm comfortable with going into the pump, servos and valve body but haven't ever gone any deeper.
Thanks again,
Bob

 

[bnewsom]

Got the trans out and started into it last night. Found a couple of interesting things but no obvious cause of low pressure. Any help finding cause of low line pressure would be greatly appreciated. Due to lack of room I can't remove just the transmission. It took about 3 hours to pull the engine/trans and guessing it will take another 4 or 5 hours to get it all back in and ready to test. Might as well say I'm begging for guidance to keep from having to do again.

The paper gasket behind the pump had some damage but I don't believe it was where it affects passages. Looked like the pump had been remove by screwdrivers wedged between the back of pump and the case. Pump is an 088, has 10 vane pump and all looks good on the inside but I will check clearances. The slide seal and support looks good. There are two slide springs - an inner and outer. The is no severe wear on the surfaces where the vanes or rings contact it but can tell there is a contact pattern. It does have the good rings and hardened stator.

1-2 accumulator piston did not have a spring installed.

The 3-4 piston was installed with spring at the top and piston flipped. My ATSG booklet shows it both ways according to model but mine is opposite of the BRF direction. Can tell by wear on plate it was originally installed with spring contacting the plate.

The PO told me something had been modded to make lockup firmer. The checkball and cage is not there but he said he thought something was done to the pump that involved a drill. Any ideas on this? I hate to quiz the PO on it any more since he basically gave it to me.

I've used a Transgo SK-200-4R shift kit before along with a CK 1-2 servo and larger boost valves and liked the way it shifted - firm but not harsh at light throttle and rock solid at full throttle. I'll probably put it back together using this kit again since it is just a street car that will see no strip action.

Right now I'm still hoping something is either stuck from sitting or was taken apart and put back together incorrectly since it was ok when pulled. I know enough to not be afraid to tear into it but not enough to really know what to look for. Sorry for the long post but trying to provide good info.
Any ideas and opinions appreciated.

Bob

 

[bnewsom]

Found an extra checkball in the valvebody. The one for the tv exhaust was not in place which I understand from reading is usually left out. It has an extra one in the vb with location pointed to with red arrow in attached picture. It is on the opposite side of the plate of where the middle of the three lower checkballs goes. They would be blocking off the same hole depending on flow direction. Could this be my cause of low pressure across the board?

 

[clusolynn]

What torque convertor did you install? While it is out, you can re-assemble the pump and see how well it fits the convertor. Then remove the pump from the convertor and insert the input shaft to make sure the splines line up and the TC guts should turn with a little drag. Let us know and good luck, John.

 

[bnewsom]

What torque convertor did you install? While it is out, you can re-assemble the pump and see how well it fits the convertor. Then remove the pump from the convertor and insert the input shaft to make sure the splines line up and the TC guts should turn with a little drag. Let us know and good luck, John.

Hello, its just a stock converter. I have fitted the pump into the converter and all seemed OK. I'll try the input shaft fit when I get to the shop. Is this the shaft that is different between the 27 and 30 spline version? Any ideas on the checkball out of place?
Thanks,
Bob

 

[clusolynn]

It is but, they are all 27 spline in the TH200-4R variety. The early TH700-R4 converters were interchangeable with the 200s but, the later, 30 spline were not. That's what I was getting at, didn't want to insult you and ask if you knew what converter you had but.. where did the converter come from? Any luck anywhere else? Good luck, talk to you later, John.

 

[bnewsom]

It is but, they are all 27 spline in the TH200-4R variety. The early TH700-R4 converters were interchangeable with the 200s but, the later, 30 spline were not. That's what I was getting at, didn't want to insult you and ask if you knew what converter you had but.. where did the converter come from? Any luck anywhere else? Good luck, talk to you later, John.

Don't worry about insulting me, my transmission knowledge is limited and I can use all the help that I can get ..... The guy I got the tc from had several lying around(all were capped) and I got the one that he thought was the lower stall version to work well with my big engine. It looks like a stock converter. It never occurred to me that it could possibly be a 30 spline. But I did just slip it on the input shaft and it seems to engage correctly and can tell by the drag when it is turned. The sticker is missing but it has "H-9" stamped on it all the way around it. Other sets are " HX005301AA-29 ", " K1H93 " and " IS 3K1S1" but I have not found anything on them. Thanks for any guidance.
Bob

 

[Steve V]

The checkball was just in that passage where the red arrow is? They go in the "bathtubs".

 

[bnewsom]

The checkball was just in that passage where the red arrow is? They go in the "bathtubs".

When I pulled the valvebody plate I found a checkball in that spot which is the wrong place. I was asking if it being there could have been the cause of low pressure on my gauge. The passage is labeled as 2nd clutch and with that ball being there, flow was blocked in both directions. Does anyone know what affect this would have had?

 

[Steve V]

I bet it would affect 2nd clutch,the rest of the pressure across the board???not really sure.

 

[bnewsom]

Hopefully someone can jump in and help me sort it out. The pump looks good but haven't pulled the pressure relief spring/checkball yet. Hoping there is trash or something under the ball or even the ball was left out. Other than the pump to body gasket being a little rough and the checkball out of place in the vb, I can find anything wrong. But somewhere pressure is bleeding off. Really don't want to go deeper since I don't have some of the special tools

 

[bnewsom]

Just went through the pump. Check ball and spring for pressure relief both ok and no trash. Cleaned everything up and assembled the halves dry. Before putting the halves together I laid green plastigage over points on the slide, rotor, ring and vanes. Tightened it up and the took it apart again. Clearances ranged from .0015 to a heavy .002 but not near .003. It's not the right way to measure but I guess it gives me an indication that this is not where I'm loosing pressure. As always thoughts and ideas are welcome.

 

[bnewsom]

I think I found the problem. I cleaned everything up getting ready to do the final assembly on the pump

and decided to pull the pump out of a core to compare it to. I found where a 1/4" hole had been drilled and tapped into the port that the filter slips up into. The hole was higher up than the filter neck reaches so it was allowing the pump to pull in air instead of fluid. Any idea what this hole is there for? Should I be looking for any other modifications elsewhere that could relate to this?