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JJSmitches
03-11-2005, 03:18 PM
I know temperature and fluid pressure are concerns for automatic transmissions. Is anyone running temp and pressure gauges to monitor a 700r4? I was looking at a 0-300psi pressure gauge but dont really know what range the temp should be in, there are a couple options available.

I have NEVER installed a 700r4 but am going to have the help of my uncle who is a mechanic at a GM dealership help out. I was reading on one popular transmission dealer's website that they require a pressure gauge be used to check operation when the trans is installed or the warranty may be void.

myclone
03-11-2005, 03:42 PM
I know temperature and fluid pressure are concerns for automatic transmissions. Is anyone running temp and pressure gauges to monitor a 700r4? I was looking at a 0-300psi pressure gauge but dont really know what range the temp should be in, there are a couple options available.

I have NEVER installed a 700r4 but am going to have the help of my uncle who is a mechanic at a GM dealership help out. I was reading on one popular transmission dealer's website that they require a pressure gauge be used to check operation when the trans is installed or the warranty may be void.

I dont run a pressure gauge all the time but I do run a fluid temp gauge so heres my .02...

Youll need a gauge capable of reading up to a min of 300psi (350psi would be better) for trans fluid pressure since a well built hi po 700 can produce that much. If you want to run a pressure gauge all the time then any guage that will read 300psi will work but be aware of running hot trans fluid into the pass compartment (<that should go without saying but I said it anyways) so an isolator or electric gauge would be best IMO.

For temp it depends... Since fluid temps can reach 240+ deg on a full tilt let it all hang out WOT drag strip pass do you want to be able to read the gauge or just know that when the gauge is pegged at 250 deg its time to let the trans cool? IMO a 250 deg gauge is plenty for a street/strip vehicle that has a proper trans cooling set up since you deffinately want to give the trans a rest if temps get that high. Any higher than 250ish and the trans fluid is in its break down zone and the trans's life span is now measured in minutes not miles.

Whatever gauge you get plumb it into the fluid OUT line going from the trans to the cooler as close to the trans as convenient. Having the temp sender in the pan only gives you temps of the fluid in the pan not what the internal components of the trans are seeing not to mention it gives you a quicker reading of actual temps and may give you enough time to notice high fluid temps and save you a rebuild. If the sender is in the pan or way down stream of the fluid out port the temp readings are also delayed compared to what the actual internal temp of the trans is seeing. Having 220deg fluid temp readings from the pan does you no good since the inside temps of the trans could have been well above 300deg for a while. Basically its the same as trying to measure temprature of anything with fluid circulating around it so you want to pick up the temp reading from the fluid right after its left the heat producing components. In the case of a 700R4 best location that can be accessed by your average mechanic is the fluid out port on the trans.

HTH

gmachinz
03-11-2005, 09:40 PM
You never want to see your tranny temps get above 180-no matter what. My gauge is installed in my remote filter block coming out from the tranny and I see consistant temps of 150-155. Now, since I designed my own tranny cooler kit w/fan, shroud and relay and using synthetic Mobil 1 fluid it takes almost forever for temps to actually hit 150-155, but once there, they don't go up any higher no matter how hard I push it. I was told ideal temps for a GM automatic is 140-150 and I built my system to maintain just that. If you're interested in a kit, pm me and we can discuss details. -Jabin

Fuelie Fan
03-13-2005, 12:05 PM
Wasn't there another thread on this recently?

My understanding was that 180 degrees is for "infinite" life of the fluid (probably still service it at 100k, as you may not have oxidized it, but no filter is perfect and there's still crud that I'd want to get rid of), you can run at up to 220 and not damage any transmission internals AS LONG AS you service it every 25k miles or so. Permant damage to seals BEGINS around 250 or so. The 4l60e doesn't even go into hot-mode operation until 275.

JJSmitches
03-13-2005, 01:32 PM
I searched for "transmission gauges" but didnt really find anything at all. I also tried just "gauges" but found way too much.

The temp gauge isnt that big a deal...I had already found on the forums the best place to install etc....

Im asking more about the pressure gauge. I was reading on the bowtieoverdrive website about installing a guage on the trans and testing the fluid pressure its producing in order to make sure its working properly...but this was only something done during testing.

I want to know more about installing a pressure gauge permanently on the trans, where and what psi should the gauge read to monitor for any problems both after initial install and down the road.

myclone
03-13-2005, 03:55 PM
I want to know more about installing a pressure gauge permanently on the trans, where and what psi should the gauge read to monitor for any problems both after initial install and down the road.

While having a gauge permanently mounted for monitoring trans pressure isnt really a bad idea I think you are confusing its intended purpose with the likes of an oil pressure guage that is used on the engine. The reason I say this is because generally speaking line pressure in the trans has more to do with the teflon/O ring seal condition rather than how safe the trans is to abuse. If a SBC has 10lbs of oil pressure then you know its "loose" from high miles or lack of maint and is just a bomb waiting to go off where as a trans may exibit no pressure issues that a guage would show but may fail the first time you stand on the gas....or it may last 200k miles. A pressure gauge on a trans just isnt going to give you an idea of the units condition until its already failed but youll have already felt the failure in the drivability before noticing the gauge.

The reason BTO wants pressure readings for warranty validation is they obviously dont dyno their trans's to verify everything is good to go before shipment. By having the end user do the pressure checks it does several things 1)verifies the work they did on the rebuild was correct 2)verifies the customer set the TV cable up correctly(VERY VERY important to this unit) 3)allows them to have trouble shooting info for a later date should the customer have problems which helps them decide whether to warranty the unit or not.

The pressure readings on the 700R4 can vary widely depending on model and how its set up. If you will pick up an ATSG manual from ebay (~20 bucks) the pressure readings for various models is listed in the first page or two. If you have a custom built unit then those pressures will only give you an idea of what yours should be.

I dont know how BTO sets their units up so IMO telling you what pressure readings should be cant accurately be done. They may set their units up to run high pressure but with soft accumulator springs to keep the shifts from being brutal or they may use average line pressures and flip/block/shim accumulators to firm the shifts up. Basically there are as many different ways to "build" a trans as a SBC so stating what yourline pressure should be would, at best, be a guess IMO.

To give you an example of line pressures my moms old car (TPI 350 IROC) had a min line pressure of 85 (min tv/in park/750rpm idle) and a max line pressure of 230 (full tv, manual 1st, 1k rpm) but would spin the tires due to the hard 1-2 and 2-3 shift at WOT. Now....keeping the above pressures/RPM vs performance in mind the other example is a 90 4.3v6 S10 4wd blazer I recently worked on that had the same pressures +/-10psi but that unit shifted like grannies caddy at WOT. Do you see that while being important line pressure doesnt = a high perf trans and its more in what servos are used and how stiff the cushion springs are in the accumulators?

Heres the short but sweet version if I confused you too much with the above ramblings.
1)Line pressure checks only verify the seals were installed correctly/undamaged when the unit was built.
2)Line pressure monitoring after the unit is installed and properly set up will only give you a visual indicator long after youve already felt something fail by the seat of your pants.
3)Line pressure can sometimes be used to help diagnose a unit that has failed before its removal to make repairs easier/quicker but it takes an experienced trans guy to do it.
4)Line pressure is less important than proper TV cable set up, keeping the trans fluid cool, and how the trans was built.

IMO permanently mounting a pressure guage in the passenger compartment to monitor the health of a trans is more of a "more guages=more cool" than a neccesity but if you have the space and really want it wont hurt anything. Plus it gives any passengers/on lookers something else to look at :) .

JJSmitches
03-13-2005, 07:50 PM
Thanks for the help everyone I am passing on the trans pressure gauge. I was concerned after reading other posts about guys having issues after seting up their 700r4 trans and thought that having the gauge might help me out if there are problems after installation.