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Too much line pressure

 
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SMOKEmUP
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Joined: 30 May 2002
Posts: 3172

65175.84 points


1979 Chevrolet Camaro

PostPosted: Sun Sep 29, 2002 11:00 pm    Post subject: Too much line pressure Reply with quote

I finally was able to put a gauge on my 700R4. I got a cheap air pressure gauge that goes up to 160 psi and thought it would be enough, it wasn't.

The problem is I have to much line pressure. With no tension on the TV cable I have 120 psi, if you put a little tension on the cable it goes down to 100 - 105 psi, that's the lowest I can get it to go., this was measured in park, neutral, and OD at 1000 rpm as the test procedure says. The spec is 65 - 75, TCI recommends 70 psi (this is not a TCI transmission, just using their spec). Now when I put just a bit more tension on the cable, less than 0.5" the pressure jumps off the gauge, I'm guessing around 200 psi but the needle is buried hitting the stop on the other side so it could be more! The spec is 170 psi.

I didn't build this transmission, someone recommended a "good transmission guy" to build it. I guess he does great at stock re-builds but not at performance transmissions.

The trouble shooting guide in the manual lists several possible causes to this problem, one of them is "checkballs omitted or mis-assembled". The plan is to drop the pan and see what I have for check balls or anything else obvious. (Man to I hate getting pissed on by transmission fluid when pulling the pan!)

86GN... Dyno day is not looking good but I'm trying. I'll keep you posted.
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SMOKEmUP
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Joined: 30 May 2002
Posts: 3172

65175.84 points


1979 Chevrolet Camaro

PostPosted: Mon Sep 30, 2002 11:39 pm    Post subject: Reply with quote

In my previous post I stated incorrect line pressure numbers. Here are TCI's recommended line pressure numbers, they are 90-110 in P N -OD at minumum and 190-230 in P N OD at maximum. Since my gauge was messed up I took Paul P's advise and connected my compression tester gauge to it. It's a Home Depot special but it works. Here's a picture if you interested.




My readings were 100 psi at minimum , OK there. But at maximum the gague was bouncing all over the place, not constant pressure, between 200 - 280 psi.

Another problem is the lock up converter won't work. I double checked the electrical connection to it and that's fine, the problem is internal to the transmission.

Suggestions, helpful comments?
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SMOKEmUP
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Joined: 30 May 2002
Posts: 3172

65175.84 points


1979 Chevrolet Camaro

PostPosted: Wed Oct 02, 2002 9:27 pm    Post subject: Reply with quote

I'm hoping I've found part of the problem. After reading the troubleshooting section in the ATSG manual it suggested looking at the govenor as possible cause for a problem. I knew the govenor cover was not quite seated all the way, maybe and 1/8 out at the top and therefore I decided to take it out and look. Here is what I found.

another view, notice the shaft which halfway out, I'm amazed the spring stayed in place.


What your looking at is the govenor in a 700R4 transmission. I had installed the shift point modification kit from B&M. What happened is one of the snap clips (highlighted in the picture) came off and the rod started to pull out. The above pictures are how it looked when I took it out, YEOW! Shocked .

I was unable to find the missing clip so I put another one in and re-installed it back in the car. I'm very nervous about the missing clip if it could mess something up inside, we'll see (hopefully it will get picked up in the filter, or it came out already and I just missed it).

I didn't have time to take the car for a test run becuase it started to rain and I had a bunch of tools to clean up so I'll try it tomorrow and hopefully that was the problem.
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86GN
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Joined: 10 Jun 2002
Posts: 290

4042.20 points


1990 Chevrolet Corvette

PostPosted: Thu Oct 03, 2002 8:21 am    Post subject: Reply with quote

Cool Good to hear
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Paul P
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Joined: 15 Aug 2002
Posts: 2454
Location: Townsend, Mass.
83266.64 points


1971 Chevrolet Chevelle

PostPosted: Thu Oct 03, 2002 8:37 am    Post subject: Reply with quote

Looks like a problem. Stick a magnet on the bottom of the pan if your nervous. It will stick to it if it 's sitting in there. It won't pass through the filter anyway. Good news though! Wink
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SMOKEmUP
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Joined: 30 May 2002
Posts: 3172

65175.84 points


1979 Chevrolet Camaro

PostPosted: Thu Oct 03, 2002 11:08 pm    Post subject: Reply with quote

I think that was a good part of the problem. The transmission still whines a bit but not nearly as bad and the lock up still doesn't work. But the rest of it seems good. I set the max line pressure for about 210 psi and it seems to be ok, leave it in drive and it shifts at 5500 rpm which is about right for that cam I think. Therefore maybe I'll make the chassis dyno and even the track this year. The numbers will be sad but at least I'll make it there.
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