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-   -   700R4 Line Pressure (http://www.hotrodders.com/forum/700r4-line-pressure-227637.html)

Edgar86 12-27-2012 07:04 PM

700R4 Line Pressure
 
Hi all, I just finished rebuilding a 700 R4. I am very pleased with the shifts (transgo kit & larger boost valve). However, in checking the line pressure I have 90 PSI in neutral, 210 in reverse and 150 in all other gears. There is no change when the tv cable is pulled...or engine RPM increased. Even when driving the pressure is 150. It his concerns me; it's odd since the shifts are great. Any advice or comments are welcome. Thanks

cobalt327 12-27-2012 11:30 PM

Could be a stuck TV valve. Hard to tell just by feel because the linkage is spring loaded, so it feels much the same whether the valve is stuck or not. I'd try pulling out the cable than quickly release it. Repeat a few times and see if it frees up.

Hopefully a trans guru will have something to add.

dwwl 12-28-2012 09:49 AM

I'm not to up to speed on the 700 but they should be like the 200 4r because the use the same type of tv valve system. at idle, you should be able to see the pressure increase instantly as soon as you start to move or tighten up the tv cable. If your pressure is already high, i'm wonderilng if your cable is to tight to start with, that was my problem until I adjusted it.

Edgar86 12-28-2012 10:30 AM

Thank you for your suggestions, it is possible that the TV is stuck (although I made certain it was free during the rebuild). I have checked the cable, it is not too tight... I find it strange that the pressure is at a constant 150 PSI in the forward gears; since (I think) the TV pressure & pressure routed by the governor "fight" each other to make each shift. I believe I should see poor shifting due to no pressure change when the TV is applied. I am worried that I will not have enough pressure during WOT...possibly burning my clutches.

Crosley 12-28-2012 02:34 PM

minimum cable setting on the TV cable is important if the 'fail safe' check ball is in the valve body. This check ball is larger than the other .250 sized check balls.

The trans in fail safe mode will operate at full line pressure, shifts will be late like WOT . You seem to describe this symptom

Edgar86 12-28-2012 03:06 PM

Thanks Crosley, I'll check the cable tonight. I had no idea that the large check ball was a line pressure "fail safe". I did re-install it during rebuild... my question is (if you don't mind) why do think some builders remove this check ball? Would it not provide protection in case the TV cable broke or became disconnected?

dwwl 12-28-2012 03:37 PM

I know my shift kit came with a special check ball when i rebuilt my 200 4r. I will have to go down stairs and look at my book and left over parts and see what i've got. I've got a second one on the tranny stand and have to look and see how it is set up. :D yep, your right crosley, there is a difference and it even makes note of it in the paperwork i've collected. I have no idea what would happen if you left it that way, but i'd think you would be ok as far as pressure is concerned, but i'd worry about second gear starts and that will cause you some real problems. I think some of the pressures that are recommended you should see, seem a little to high. I run .471 boost and larger low/reverse valves and my max pressure is 175-180 and 225 in low and second. Running down the road in 3rd 4th is 160. anything more than that, i'd have to run a 500 mega valve, and maybe that is what they think everone should be running. So if you haven't dameaged anything, you could just change that and be good.

Crosley 12-28-2012 05:18 PM

Quote:

Originally Posted by Edgar86 (Post 1628064)
Thanks Crosley, I'll check the cable tonight. I had no idea that the large check ball was a line pressure "fail safe". I did re-install it during rebuild... my question is (if you don't mind) why do think some builders remove this check ball? Would it not provide protection in case the TV cable broke or became disconnected?


Yes the fail safe check ball works well in most situations. When folks started installing the 700 - 4L60 trans in to various applications, geometry of the carb linkage would often be incorrect.

Folks could get a tight cable at WOT , but the minimum setting would be loose on the cable and the trans would go into 'fail safe ' mode.

You may also have a worn TV valve bore in the valve body.. the oil can get behind the valve and move the valve to full apply.

:pimp:

Edgar86 01-03-2013 11:08 AM

Thank you all for you replies...sorry I took me a while to get back to you. You were right Crosley; the TV cable was loose. I adjusted it and the issue went away. The transmission was running in "fail safe" mode the whole time. Now I need to figure out why my lockup isn't working...haha!!


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