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Old 10-25-2013, 07:56 AM
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700R4 low pressures?

Hi folks, I am getting ready to go into my 700R4 to do some more mods and correct some errors I made in last winter's build. I did before work pressure tests this morning and got some troubling results. Minimum TV, in P, N, D, 3 @ 1,000rpm, pressure is 90psi which is fine. But then in reverse, pressure @ 1,000 is only 110. In manual 1st and 2nd, pressure @ 1,000 is still just 90 psi. Full TV, pressure in P is 105. N is 110. D is 95. Man 3rd is 100. Man 1st and 2nd is 100. When I raise rpm to 2,000, pressures @ full TV are P & N- 220, R-210, D 190, 3-200, 1&2-210. Gauge is steady(no wiggly needle). In R, D and 3, when I rev the motor with the TV locked full open, pressure jumps to 240 before falling back off to the readings listed above. I wonder if that might be the pressure relief valve opening. I would like that to hold til 300psi if possible.

The unit has a .296 rev boost valve and the .500 TV boost valve with a high rate regulator valve spring. I have dual springs on the line bias valve and a new 10 vane pump. I expected much better readings. My ignorance is that I put the unit together and drove it most of the summer without pressure testing. Won't make that mistake again. To make things worse, the TCC never worked since the build and I know I got it hot. I know that there are probably several things that could cause this kind of behavior. Does anyone have any thoughts? What jumps to the front of your mind? Sealing ring(s)? Damaged pump? Gasket blown? I plan to go into the unit first thing in the morning and have the weekend to get it back together. I have a full gasket set, new sealing rings, and some other goodies to put in it. If I need other parts, I will need to run to Portland tomorrow to get them. Up side is that it is coming winter and I don't drive the car in anything but sunshine. Worst case is I find something wasted that I can't get tomorrow, I put it back together best I can, limp it home and go back in later better prepared. Moral of this story is pressure test before you drive it. Damn!

I am very thankful for any help. Go ahead and chew my butt. I've earned it.

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Last edited by ASE Doc; 10-25-2013 at 08:05 AM.
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Old 10-25-2013, 09:20 AM
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Just found a post by briscoe in another thread saying that my kind pressure readings likely point to a pump issue. I'll see if I can find a good pump locally today.
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Old 10-25-2013, 10:11 AM
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Tried to reply to you and it went somewhere ? So here it goes again. I would agree that I think its your pump, since your pressures are low across all the gears. Since you've got the kit, look at the clutches and see how much wear. A good indicator will be the amount of stuff is lying in the bottom of the pan. Buy the gauge set. I test mine twice a year. First when I get it out of the garage in the spring and then in the middle of the year when its handy. When if first built my 200 4r, my pressures were ok, but not like they were suppose to be. Found that when I rebuilt my pump and did all that work to it, I forgot to put the bigger valves in it. So don't feel bad, it happens to all of us. Doing you pump over may not be ok unless its done right. It maybe worn, and only a new pump will be your answer.
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Old 10-25-2013, 10:52 AM
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That does suck for me. I put this pump in last winter about 2,500 miles ago. I had it open to install the high rev slide spring. Maybe I screwed it up. I thought I was super careful with it, but. I can get a new one at PTW in Portland but I will have to leave the shop early and run there today since they're closed tomorrow. I'll tear the pump down in the morning and see what may have happened to it. If it looks okay, I'll look for sealing rings or anything else that may be dumping pressure. It is awful strange though that pressure at idle, min TV is so good. Wouldn't a bad pump cause low pressure period? Maybe not.
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Old 10-25-2013, 12:12 PM
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i'm no expert on the 700 or 200 pumps. When I rebuilt my 200 4r pump, I upped it to a 10 vane from a 7 vane, and used the larger steel rings. I was told that the harder steel rings are a fraction larger which helps keep the pressure up when it gets warmed up. I didn't use the high rev springs on mine for mine was going to be used in a lot of high rpm's. I did open up the return passage a little to prevent seal blow out.
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Old 10-25-2013, 01:04 PM
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Mine is a 10 vane with the steel rings. I'll check it out and look for anything I might have done wrong.
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Old 10-25-2013, 01:11 PM
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Brisco left HR long time ago.

Your problem with low reading of PSI @ 1000 rpm is all pump. It is set up too loose. Clearances too loose on slide, on rotor , the side clearance is too loose on those pieces.

Pump cover may not be flat. Was it checked? Was it surfaced to flatten it?

If you had proper testing setup, flow gauge and psi reading on cooler lines.... That wil drop to nothing, indicates weak pump.
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Old 10-25-2013, 05:44 PM
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I was just going the say that. To much clearance between the the halfs.I flat sanded mine on glass using spray on adhesive an 400 gr. wet/dry & WD 40. I did both sides & the stupid thing was I didn't measure. Use a flat edge an a feeler gauge. I didn't know this at the time but a very good flat edge is a drafting square an I have one, just didn't know about this at the time. Just have to be careful with the plexy glass edge. I forgot what the clearance should be if I remember right its pretty tight.

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Old 10-25-2013, 06:10 PM
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Here's some really good info.
[url]www.uscars.biz/uscars/extras-docum...700r4
Sorry I can't cut n past.

Last edited by dogwater; 10-25-2013 at 06:16 PM.
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Old 10-25-2013, 06:18 PM
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Set up the rotor first is what I do, .0015 to .002 side clearnce. Set rotor into pump pocket, measure with depth gauge

The check the slide. Since the slide has a rubber O-ring under the sealing ring, you can run .003 clearance on the slide
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Old 10-26-2013, 06:23 AM
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Thanks guys for your help. I tore the unit down this morning and found the pump casing chewed pretty good. I also found where I missed filing down a couple of plugs in the separator plate. I'm sure these plugs created a nice cross leak. Now the bummer is that I missed my chance to pick up a new pump yesterday in Portland(too much work to leave early). Now I may be stuck until Monday.

Good news is, besides a fried, and I mean wasted 3-4 clutch pack, everything looks good. I guess one down side to the huge 3-4 clutch capacity of this Smart tech housing is that when the clutches fry, they really leave a gap. Clearance right now is a spacious 1/4 inch I bet. A little expanded from the .040 that I set it at last winter. The friction material is completely gone from every friction plate. Amazing they would still apply at all.

I will not run this unit again without verifying pressures first. Just because it seemed to shift great obviously doesn't mean it's all good. I must have screwed something up in the pump. I think maybe I didn't use a good enough assembly lube. This time, I'll just use my Fed Mog engine assembly lube. It's a much better lubricant than the trans gel. I was afraid this would happen. There is alot of non ferrous metal in the fluid too(metal that isn't attracted to the magnet). I wonder if the converter took a dump on me. I'm thinking the Edge unit that's replacing it will do better. Especially since I'll have the lock up working before it sees the road. It makes sense that everything was fine until I ran the car on the freeway in slow traffic on a very hot day. I'm sure that was when I fried the converter and probably started the destruction.

This will have been a great and expensive learning experience when it's finally done. I have learned to be much more patient and thorough. At this point, for what I have invested in this transmission over the time I've owned the car, I could have a custom built T56.
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Old 10-26-2013, 07:24 AM
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You'll be a 700r4 master mechanic. Your doing great job. The pump an the valve body are the only two things that you can't check to make sure they work until there in the car an running.
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Old 10-26-2013, 09:01 AM
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New issue. I cleaned up the input housing, removing about a pound of friction material, and found that the input shaft is worn down at the front support bushing point. When I put the pump together, I followed a method I found on line to align the pump halves by installing the bolts loose, bolting the pump in place in the case, then tightening the pump bolts. It seemed like this would work out okay. But now I find that the input shaft is worn at the converter end. Is it possible that misalignment of the pump halves caused this? It doesn't seem like the halves could have been off by that much. Or is it just the converter being a pile. The input shaft in my old housing is in good shape. Has anyone ever tried removing an input shaft from the housing with the reinforcement ring installed?
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Old 10-26-2013, 11:20 AM
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WOW I used a very long wide band that I had that looked like a giant radiator clamp, to put my pump back together. Being a novice transmission guy, is why I use the pressure gauge several times a year. Sounds like you've got a major rebuild ahead of you. Don't get down. Think of it as fun and experience. I've had my pan off my tranny so many times I think I will wear out the pan bolts. Rebuild it again You've learned a lot and know put it to use.
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Old 10-26-2013, 02:57 PM
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Got it! I warmed the housing up gently with a propane torch to loosen the sleeve retaining compound. The shaft came out clean and nice. The other one went right in.

I checked out the pump to case clearance to see how tightly the pump is held in alignment by the case. It is within a few thousands. The pump is very snug in the case. The band clamp couldn't be much tighter. I am thinking that this pump or the converter was out of whack. I remember no issues with the stator support going over the shaft on assembly. Still, it is a possible issue. I might see if a local trans shop can do the pump assembly for me.

I did have one other disappointment today. I wanted to set my TCC up to have lock up in 4th always and selectable lock up in 3rd using my old fog light switch. I found out that my valve body doesn't have the 3rd clutch pressure switch passage drilled. Even if I did drill it, it appears to feed off the 3rd accumulator circuit which is now deleted in the Transgo shift kit. Oh well. I'll go with what I've seen on Tony's pages and have lock up in 4th and selectable lockup in all but 1st gear. I guess that the 700R4 be design won't activate the TCC in 1st so with 12v applied to the TCC solenoid, you get lock up in all but 1st. I'll try it and see if it works out.
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