Using a Transmission Pressure Gauge | Ford Explorer - Ford Ranger Forums - Serious Explorations
  • Register Today It's free!

Using a Transmission Pressure Gauge

Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
THIS one I started in the right forum (unlike my Rebuild Diary). There is starting to be more discussion about transmission issues around here, and I think numerous posts and threads and input from so many good sources has spurred that. Brian (I think his nom de plume here - Brain is a misspelling - but it fits, he is incredible with what he is doing) has provided even more fuel for the fire.... I want folks to know a trannie CAN BE a DIY project.... it is not rocket science.

Anyway I am not trying to pretend I know a lot about using a pressure gauge. In fact I didn't even own one until about a year ago. Yet... I think they are not often used, even by transmission shops. Why? Well at shops it really doesn't matter what part inside is not working right... they will pull it and rebuild it..."$2000 please.... thank you ma'am.... I haven't a clue what it was but I fixed it..." (and if you rebuild it all you will). And in fairness if you pull a high mileage trannie, you should rebuild it! Yet... I wanna have some ideas what is good and what isn't..... and on electronic trannies.... nice to know if the guts are ok and the "brain" is not working right (was true big time on some 2000 model year trannies!). SO, the modest pressure gauge.

A transmission pressure gauge is just a 300 lb gauge on a long hose....

15286DSCN5144.jpg


This one is made by KD tools. I picked it up off E-bay for $40, never used.... and as luck would have it the threaded end, without adapters, fits the A4LD case pressure port perfectly...

(pic coming)

I plan to hook this up to my A4 with 209K on it and record and share pressures, then do the same with the rebuilt I'll be putting in... with a NEW pump etc.......

but, until then, we can discuss what the "ideal pressures" are, and discuss what variations might mean.... as ever, everyone should feel free to join in.
 



Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.





james t

Elite Explorer
Moderator Emeritus
Joined
January 27, 2002
Messages
10,666
Reaction score
10
City, State
Texarkana AR/TX
Year, Model & Trim Level
94 SAS sport
Out of curiosity.... check and see if there is any pressure in park once you get it in. Ive often wondered if the pumps on the A4LD's run in park or not.
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
General Concepts

An automatic transmission is a hydraulic marvel... I laughed when I saw the post in Brain's thread calling it a slush box.. long time since I heard that.... yet, in some ways it is.

Let's examine the hydraulics in a general way. The engine turns a pump.... the pump, anytime the engine is running, will be pumping. That means there is a pressure. We can measure that pressure... at idle, at fast idle, and with the throttle wide open... and see how it responds.... SO, first thing we might learn is... how healthy is my pump?

Next we can measure pressures in various gear settings...what does this tell us that we might not already know? Well.... each gear involves a combination of clutches and bands.. all hydraulically applied. If we do not get the expected pressures in a particular gear, then we can hopefully isolate the components being hydraulically actuated in that gear, and from that figure out or narrow the candidates for leakage, and hence the "culprits".

Remember the automatic transmission hydraulically applies a band, or engages a clutch or both, to make a a gear. If something is slipping.... good chance we can catch it with a pressure gauge. Does that fix it? No, but it helps us understand the what why and where....knowledge is power.

Next up....ideal pressures and what we might look for as we investigate gears.
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
James the pump is driven anytime the engine is running. Park is just neutral with a pawl engaged. In fact on the A4 the expected pressure in park at idle is 57-78 psi, same as neutral.

In fact lets look at the book. While these may vary depending on the transmission application... here are the general values...I'll use a 1993 A4LD as the norm...

Idle.... Park/neutral: 57-78; Reverse: 67-105, OD, D, 2, 1: 57-78; Fast Idle.... Reverse: 157 - 170; OD, D, 2, 1: 114-135; WOT... Reverse: 282-316; OD, D, 2, 1: 205-235.

So now we have some idea what to expect.
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Let's assume we have hooked up our pressure gauge, and the engine has been started and is idling. If we run through the gears and find everything within the expected pressure ranges, it tells us that the pump and pressure regulator are, so far, ok. High pressure means a pressure regulator is malfunctioning, or maybe a throttle valve (think modulator) is stuck... Low pressure here means a lot of things... pump maybe, pressure regulator... even things like a plugged filter or massive internal leakage in a myriad of places... tough to track but not impossible. A plugged filter often though will show as a decreasing pressure at higher RPM's.... If your presure regulator is stuck, the line pressure should stay pretty constant throughout the RPM range. Another possible clue. Even internal leaks will often show up in their respective gear ranges.... so, all is not lost....

next, increase the idle to a fast idle... compare readings... by now we are looking for either a confirmation of what we found on the idle tests, or possibly a clue in one gear or another of an abnormal reading...

A forward clutch that leaks won't show up in pressures in park, neutral or reverse, but it WILL in any forward gear. A significant servo leak should show up any time that band is applied. A low reverse servo leak should show up in a lower than expected reverse, and a 1st gear lower than the other forward gears.... and so on and so forth. A chart of the bands and clutch packs applied in what gear can be a BIG help here.

WOT (Wide Open Throttle). This is more or less a stall test in each gear. It puts maximum pressure on the seals and servos and may help isolate the offender. In reverse is is the absolute test of the pump as well.

This test is best done with the parking brake set, the regular brake firmly pressed and a brief pushing of the throttle to the floor. It WILL heat up the trannie, so don't over do it.. it is a tough test on an aging trannie.

Anyway that's an overview, we'll look at real life readings soon.
 






james t

Elite Explorer
Moderator Emeritus
Joined
January 27, 2002
Messages
10,666
Reaction score
10
City, State
Texarkana AR/TX
Year, Model & Trim Level
94 SAS sport
Glacier991 said:
The engine turns a pump.... the pump, anytime the engine is running, will be pumping. That means there is a pressure.
Not true on the Dodge truck auto's.... the pump doesnt run in park and a known longevity "fix" is to shift the truck into neutral after its cranked and let it sit for a few seconds before going into drive or reverse. I didnt know about the various Explo V6's trannies.... just thought id ask. Thanks for the info. :thumbsup:
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Interesting. I accept what you say as correct but am curious. I thought all TC's were more or less the same... and if the TC was turning, it was a direct mechanical connection to the pump gears (like in the A4/4R and 5R). I'm constantly learning.
 






cjbarron5

Well-Known Member
Joined
May 20, 2004
Messages
256
Reaction score
0
City, State
Ashland Mo USA
Year, Model & Trim Level
96 XLT
????????????? worked in a tranny shop for 2 years and didnt know that about dodge although i have only rebuilt one dodge tranny as far as the explorer and the chevy trannys glacier is right in park it is like neutral the tranny just goes in to a fluid bypass loop ive done a lot of trannys and am glad i learn new stuff here all the time as well as offer a little too
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Picture Post of Gauge in Use

I hooked up the gauge. Ya know how you often curse the "easy" pics in manuals, a far cry from reality under the car? Well it fit here, and I was the one showing the "easy pics".. I ended up unhooking the shift cable and after that was ok. I did have to use some of the "plumbing parts" that came with the gauge.

15286DSCN5225.jpg


ultimately I hooked it up near the mirror, I'll tape it for daily driving for a while and see what I might learn...

15286DSCN5233.jpg



15286DSCN5231.jpg


(and no comments on the paint, it's being prepped for a nice gloss black base/clear job this fall... yah, that'll be a "Diary" too)

Now, remember this trannie is just OLD (209K) and it's only complaint is uphill on a hot day.... that said lets fire it up

Here is idle pressure right after fire up.. (remember norm is 57-78 - and I am cold)

15286DSCN5210.jpg


Then reverse.... as expected the boost valve has upped the pressure
(norm is 67-105 - and still cold)

15286DSCN5211.jpg


I cannot explain the high reading except cold oil...

then into neutral (*same as park hydraulically...)

15286DSCN5213.jpg


I cannot explain the slight difference... but it wasn't apparent once things warmed up... N and P were identical. On to OD...

15286DSCN5214.jpg


no change....

then D

15286DSCN5215.jpg


and then manual 2

15286DSCN5216.jpg


and finally into manual 1st.... I am at a loss to explain this reading, thinking maybe the trannie was starting to finally warm up... in fact this lower reading became the norm from here on in idle... so I think that is what happened...

15286DSCN5217.jpg


for here we are back in park

15286DSCN5218.jpg


I'll save a pic... the line pressures in park and neutral stayed here regardless of the RPM.... so we are going to start a fast idle series.... pretend the last pic at park was the starting pic for that series, because the pressure stayed right there.... nest up, fast idle, reverse.... looking for 157-170 PSI (course what IS a fast idle? was 1000 - 1200 RPM's high enuf?)

15286DSCN5219.jpg


I consider this ok... 157-175.... on the slightly low side but....

then on to Neutral... see, same as idle...

15286DSCN5220.jpg


then OD

15286DSCN5221.jpg


a little low....

then D

15286DSCN5222.jpg


same low

and manual 2

15286DSCN52221.jpg


finally manual 1... there is a change, and I cannot explain it...

15286DSCN5223.jpg


finally back in park, at idle...

15286DSCN5224.jpg


The only test left was the WOT test. I pressed the throttle to the floor, or close anyway, in each gear, in every case I more or less pegged the gauge... I didn't do an extended test here for many reasons... but I was satisfied the pump was doing a decent job, and the pressure regulator was working...

OK... you may be saying .... what did THAT prove? Good Q. Here is my answer. This is NOT a sick trannie, it is an old trannie. NO ONE bad spot, a lot of aging parts and seals... The warm idle pressures were a tad low, as were the fast idle... pump? nope. particular seal or part? nope. I believe that it was a combination of things. I may drive it a bit and leave the gauge installed, but for now, call this thread your reference.... your results should be somewhat similar...unless you have a trouble spot. We'll compare pressures on the new trannie once it is installed.

Ok why is mine overheating? I think the OD band is slipping a tad...and when it gets real hot I bet the servo is leaking, a viscious circle. I didn't prove that tonight but really wasn't expecting to. Remember we are all learning together here. I am no expert with this. Just want to share and invite input.

At least we know why R sometimes works when nothing else will (e.g. low fluid situation).
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Well I have been driving this with the gauge on the mirror as the pics show... it is interesting to watch. On initial drive engagement as I step on the gas the pressure gets to 125 pretty fast, then SNAPS quickly back down to about 70 or so. My guess is a sticky valve.... not a driveability issue, but interesting. That is the only place that happens. In typical driving the pressure is around 60-70 as I cruise along. If I accelerate, or encounter a slight incline the pressure rises in proportion to the strain... a freeway on -ramp acceleration gets me up around 90 to 100 PSI but as I come up to speed it slowly bleeds back down the that "normal" value of around 70 PSI. I am assuming the regulator is doing it's job. Reverse is higher as we saw, but with a nice warm trannie pressures barely hit 120 PSI.... probably the L/R servo seal leak.... I have a definite delayed reverse engagement - not a prob, I know what it is and I am a patient man. (g). Mos'ly anyway.

Once I get the new trannie in and checked out I'll run these again and we can compare pressures. I just thought folks might find this of interest.
 






Brain

Well-Known Member
Joined
June 14, 2004
Messages
915
Reaction score
3
City, State
Golden, CO
Year, Model & Trim Level
'92 4X EB and '91 4X XLT
Hey Glacier, I was wondering what your thought are of increasing the pressure by something like 10 psi over stock. The boost would add the same amount of pressure, but would add it to a higher "base" pressure. If I do this, I'll be making a modification so that the cold pressures aren't that different from the warm pressures (by enlarging the hole that feeds pressure to the pressure regulator valve). I can choose how much to increase the baseline regulated pressure by quite a bit, but I'm trying to come up with a value that would help engage Frankentranny's larger servos and OD clutch piston a little faster. I figure that because those servos and piston have more volume to fill, raising the pressure a little bit would help fill that volume faster so that I don't have any issues with the activation timing (such as a delayed band application would causing over-revving). I don't want to go overboard on it because the rev/high, forward, and reverse pistons and servos are the same (although the timing wouldn't really matter that much with the forward clutch or reverse servo). So three out of four "active" elements have larger volumes. Thoughts? I've already cut an insert to raise the main pressure 20 psi, but I'm thinking that is a bit excessive (and it is easy at this point to reduce it down as much as needed).
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Brian... when you look at the range for "normal" the spread is about 20 lbs... suggesting this isn't driven by some magic number as pressure. Higher pressures could certainly have some benefits - to a point. Here are my thoughts con in no particular order: 1) Once a band is applied and stopped rotation, additional force applied to the band only increases chances of band breakage. 2) The accumulators and in fact the entire timing system may be dependent on a certain range of pressure (I really don't know how true this is - sounds like you have a good working knowledge on this). 3) Pressures higher than needed could accelerate wear unnecessarily or increase internal leakage.

On the flip side: Higher pressures will mean firmer engagements with less slippage, less heat and less wear on clutches and bands.

So I guess that's the best I can come up with. I think I'd not be overzealous - maybe 10 psi is plenty. Btw...How were you able to calculate the increase in pressure?
 






Brain

Well-Known Member
Joined
June 14, 2004
Messages
915
Reaction score
3
City, State
Golden, CO
Year, Model & Trim Level
'92 4X EB and '91 4X XLT
It's kind of a long explanation, and I'll post it more in depth in the Frankentranny thread, but I measured/calculated the spring constants (for both the 5R55E and A4LD) for the main regulator springs (the larger diameter ones) by measuring the free length (zero force) and partially compressed length with a certain weight (in my case it was 5.53lb). With thse spring constants, the only other thing needed was the diameters of the main valves, which turned out to be 0.398" for the A4 and .420" for the 5R.

So for the A4LD, I got a value of 47.7 psi/inch. This means that if I want to raise the pressure by 5 psi, I would insert a spacer with a thickness of 0.105" (47.7X.105=5). A 10 psi increase would be 0.210", etc...

For the 5R55E, I got a value of 71.3 psi/inch.

The other thing that is a limit to how much you can "safely" raise the pressure is how much the main spring can be compressed before it is fully compressed and doesn't allow the valve to open (vent) so that the pressure can still be regulated.

Here's a picture of the regulator valve assemblies (5R55E on top, A4LD on bottom):
27133R-001FB.jpg


So basically, I'm putting in a spacer that will preload the main regulator spring, so it has the same inner and outer diameters as the boost valve sleeve (a little smaller for each diameter to make installation easier). This leaves the boost the same, it just raises the baseline regulated pressure -> so if it normally had 60 psi at idle and an additional 20 psi of boost (to give a 80 psi reading) in a particular gear/engine speed, it would have 70 psi at idle and an additional 20 psi of boost (to give a 90 psi reading).
 






Brain

Well-Known Member
Joined
June 14, 2004
Messages
915
Reaction score
3
City, State
Golden, CO
Year, Model & Trim Level
'92 4X EB and '91 4X XLT
Oh yeah, I was going to say something about the broken bands as I think they might be related to this valve. There is one itty bitty hole in the separator that feeds fluid (the input) to the regulator valve (left side in the pictures), and if this little hole gets plugged, the pressure could be unregulated and go as high as the pump output. I could definitely see broken bands in that situation - they would probably be the first thing to go from an over-pressurization problem. I'm considering drilling out that hole a bit bigger and maybe even putting on a domed screen (to make absolutely sure it doesn't get plugged up).
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Well for damn sure take pics of it! I learn something new from you every day.

Eventually it would be fun to do a joint project final thread on a TRUE, best effort, as close to bulletproof as possible A4LD. I'm betting it will have machine work inside and the guts from a 55N/S or W, and other mods.
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
A few folks have asked about the location of the connection... heer are a couple of pictures taken with the trannie out of the car, and, as compared to installed, upside down... it is very near the shifter linkage bore:

shown on the empty case, with the plug removed. The bore ahead of it is the throttle shaft/shifter bore.

15286DSCN5116.jpg


here it is (bad pic, sorry) on the transmission as it is assembled...

15286DSCN5118.jpg


The bad thing about painting a trannie black is that it does not photo well. Here is a recently acquired A4LD case... still dirty and much easier to see the plug. I am using an inspection mirror to point it out...

15286DSCN5549-med.jpg


this is on the driver's side, just behind the shift linkage. It is easier to attach the fitting if you pop the linkage free (it does just "pop" off too, and back on)
 






mctoy

Well-Known Member
Joined
May 31, 2004
Messages
272
Reaction score
1
Man,....like evesdropping on a conversation between a couple surgeons! Really appreciate both of you guy's educating the rest of us! Breathlessly awaiting operahouse's comments :D Really have learned alot of rocket science (Auto tranny's) by reading your replies to questions and posts! Question: Would increasing pump pressure slightly reduce or eliminate T.C. shudder? If so, how would you do it on a Ford (5R55E) ? I know the Chevy guy's can get an electrical adapter cable that 'reprograms' everything for them. Thanks again guys for sharing your knowledge!
 






ol_ben

Active Member
Joined
June 29, 1999
Messages
73
Reaction score
0
My Guess from the pictures of the theads it appears to ba 1/4" pipe thread. I have probably enough pieces oh 1/4 brass conectors to be able to constuct a working pressure guage?
Can you confirm 1/4" thread?

Thanks,
Ben
 






Glacier991

EF Tranny Guru
Moderator Emeritus
Joined
February 8, 2003
Messages
9,826
Reaction score
49
City, State
Sacramento, CA 95827
Year, Model & Trim Level
1992 XLT
Ben, close. 1/8" NPT.
 



Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.





mctoy

Well-Known Member
Joined
May 31, 2004
Messages
272
Reaction score
1
^Bump^ ...to see if there is an answer to my pressure question above
 






Top