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Old 03-25-2011, 01:32 PM
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T-400 whine noise problem

Hi guys!

I replaced my damaged th350 by a th400.

I rebuilt the tranny, had very good endplay on in- and output shaft, pump gears were new and within specs.
When I fired her up for the first time, I heard a very loud whine (often described like the whine of a blower) from the front of the transmission getting louder as the rpm increased and present in all gears. Fluid level was just right.

Since I read most topics concerning the whine of a th400, I first replaced the Filter, it was brand new though and checked the o-rings of the pick-up tube. No change.

I dropped the tranny and replaced the converter by a known-as-working-properly one and double-checked the clearance between the flywheel and converter. Same whine again.

Today I put on a pressure-gauge at the driver-side check port. unforunately my gauge only reads up to 120psi. Pressure was way over that in any gear.
Then I installed it at the ATF-Cooler line. (the lower one) Fired her up again and THE NOISE WAS GONE!!!!

I put the cooler-line back on. The noise came back again.
I checked the oil-cooler but it wasnīt clogged at all. I disconnected the extra oil-cooler and ran the stock cooler only. Problem solved.

But how can a perfectly clean and leakproof auxhiliary oil cooler cause the whine? I can understand that a clogged filter makes the pump draw air causing the whine.

Please help me understand this: When I replace the cooler by a pressure gauge, there is no oil flow to the cooler at all, but the whine is gone. When I hook up the stock cooler, there is flow, but no whine as well. Do you think, the auxhiliary cooler in addition to the stock unit and the few feet of extra fluid line makes the oil pressure drop, causing the whine? Or is it more likely it pulls air somewhere at the fittings? (I canīt believe this, because since it is under pressure it should leak rather than pull air, right?)

I hope this helps people having the same problem as I had. Give it a try, checking the cooler is less hassle than dropping the pan or the whole tranny.
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Old 03-25-2011, 05:53 PM
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Quote:
Originally Posted by UngerMarkus
Hi guys!

I replaced my damaged th350 by a th400.

I rebuilt the tranny, had very good endplay on in- and output shaft, pump gears were new and within specs.
When I fired her up for the first time, I heard a very loud whine (often described like the whine of a blower) from the front of the transmission getting louder as the rpm increased and present in all gears. Fluid level was just right.

Since I read most topics concerning the whine of a th400, I first replaced the Filter, it was brand new though and checked the o-rings of the pick-up tube. No change.

I dropped the tranny and replaced the converter by a known-as-working-properly one and double-checked the clearance between the flywheel and converter. Same whine again.

Today I put on a pressure-gauge at the driver-side check port. unforunately my gauge only reads up to 120psi. Pressure was way over that in any gear.
Then I installed it at the ATF-Cooler line. (the lower one) Fired her up again and THE NOISE WAS GONE!!!!

I put the cooler-line back on. The noise came back again.
I checked the oil-cooler but it wasnīt clogged at all. I disconnected the extra oil-cooler and ran the stock cooler only. Problem solved.

But how can a perfectly clean and leakproof auxhiliary oil cooler cause the whine? I can understand that a clogged filter makes the pump draw air causing the whine.

Please help me understand this: When I replace the cooler by a pressure gauge, there is no oil flow to the cooler at all, but the whine is gone. When I hook up the stock cooler, there is flow, but no whine as well. Do you think, the auxhiliary cooler in addition to the stock unit and the few feet of extra fluid line makes the oil pressure drop, causing the whine? Or is it more likely it pulls air somewhere at the fittings? (I canīt believe this, because since it is under pressure it should leak rather than pull air, right?)

I hope this helps people having the same problem as I had. Give it a try, checking the cooler is less hassle than dropping the pan or the whole tranny.

from what your describing, to me it seems as if maybe either the pump is weak, or the cooler has a restriction or maybe both?
and to do a proper pressure test, you need to get a 0-300 psi gauge.
as it is, since you have it where its easily bypassed from what it sounds, do a flow check, before and after the cooler, see if theres any change.
just a thought
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Old 03-26-2011, 10:47 AM
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Whine back again!!!!

The whine came back again!

When I block eighter the cooler line from the tranny to the cooler, or the one from the cooler back to the transmission, the whine is gone.

What could be the problem?
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Old 03-26-2011, 11:15 AM
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it is difficult for em to explain this properly;

if the pump is straining to make high pressure, the pump often will whine. Whine from high demand, whine from a filter that is partially clogged

When you close off the cooler line, the pump does have to feed oil pressure to the transmission and the cooler circuit. Since you have reduced the need for oil volume , the pump whine may stop for that reason.

On a trans dyno , one method a professional will watch is pressure in main line of trans, watch the cooler pressure, watch the cooler flow volume. This will tell a professional transmission builder how well the pump is working.

On a performance trans , as you raise pressure, cooler flow may drop and cooler pressure too .. IF the pump is not up to the task at hand.

The pump can be worn, loose clearances.

A whine can also be from the inner pump gear just barely touching the cresent of the pump under a high load.

120 psi reading in all gears on your trans is too high for a stock trans at minimum pressure in park or neutral with proper vacuum. Modified trans with shift kit will be higher PSI than stock trans
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Old 03-26-2011, 11:25 AM
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The transmission didn�t contain any oil, when I installed it. The converter was a used one. So it was already filled with as much oil, it just didn�t run out when i tilted it to put it on the shaft. I added 10 quarts of fluid. But the damn lokar dipstick doesn�t give me reliable readings. Unfortunately there isn�t enough space for a OEM tube and DS.

Do you think it is over/under filled?

So when I block off the cooler, the atf isn�t pumped into the lines and the fluid level in the pan rises for at least 1/2qt.
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Old 03-27-2011, 03:11 AM
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Trans Fluid Capacity

You need to get the Dipstick problem straightened out.
With the engine running the fluid level should be even with the Pan mounting surface. Drop the Pan & mark the dipstick with a File mark/notch.
It may be overfilled, if the Converter was close to full & you added 10qts.
Stock TH400 = 6qts. in Pan and 4-5qts. in Converter.
Trans Fluid Capacities>> http://www.tciauto.com/Products/Tech...d_capacity.asp
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Old 03-28-2011, 11:55 AM
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Transmission is definitly not over filled.

Today I realized that doesnīt shift into 3rd. Reverse, 1st and 2nd is really strong.

Could it be a valve body issue? or maybe the pressure regulator?
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Old 03-29-2011, 05:53 AM
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Last night I disconnected the cooler line and had the transmission pump fluid into a container until some air bubbles came along. Then I filled it to minimal fluid level. It seemed like the whine was gone. I could rev her up, at Park and Neutral no whine. I took her for a test drive around the block. After about 2 minutes of driving the whine came back.

@Crosley:

The pump gears have been checked for clearance and condition. It was right within specs and the gears looked like brand new.

The filter looked like new. I changed it anyway.

The fluid looks and smells like new.

No debris in the pan.

Unfortunately I canīt have it pressure testet by a professional, because there simply is no automatic-pro around!
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Old 03-29-2011, 10:09 AM
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Quote:
Originally Posted by UngerMarkus
Last night I disconnected the cooler line and had the transmission pump fluid into a container until some air bubbles came along. Then I filled it to minimal fluid level. It seemed like the whine was gone. I could rev her up, at Park and Neutral no whine. I took her for a test drive around the block. After about 2 minutes of driving the whine came back.

@Crosley:

The pump gears have been checked for clearance and condition. It was right within specs and the gears looked like brand new.

The filter looked like new. I changed it anyway.

The fluid looks and smells like new.

No debris in the pan.

Unfortunately I canīt have it pressure testet by a professional, because there simply is no automatic-pro around!

how are the o'rings that go on the tube that connect to the filter that goes into the case?
as far as having a automatic pro check it out, from this point it seems you can handle this yourself so far. do you have access to or can buy a 0-300 psi pressure gauge?
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Old 03-29-2011, 12:31 PM
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I try to get one of a local hydraulic shop. Should be no problem to get one.

Do I need a "T-Adapter" to hook it up into the cooler circuit or just a fitting to install the gauge to the diagnose port on the driverside?

BTW, is it possible to check a valvebody for propper function with compressed air?

As far as I remember, the aluminium 1-2 modulator bushing and the 2-3 modulator bushings seemed to be lightly scratched. can this cause failure?
the valves looked perfectly.
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Old 03-31-2011, 06:38 AM
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Unger:

I was not clear in my post,, sorry.

I provided a quick view on how a professional trans person would test a trans and look for possible internal problems

A gauge with higher rating would help you. The high reading you had at 120psi is too high at idle in park or nuetral unless you have a full manual type race valve body.

Race v-body operate at high pressures full time. These v-body design can put high loads on a pump and sometimes the pump will whine.
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Old 03-31-2011, 12:11 PM
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Today I removed the valve body. Checking the valves I found this:

The 3-2 downshift valve spring is very much shorter than it should be according to my ATSG manual.

Also I found some very little metal shavings around the magnet. Is this critical?

I also checked the governor. Perfect condition. Clearance and movement optimal.

Modulator works. Modulator valve moves freely.
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Old 04-04-2011, 02:10 PM
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Update

Hi guys!

As an update, this is what I did the last few days. Without success unfortunately.

I tried a long 3-2 detent valve spring.

I checked the modulator and the modulator valve. The valve flet like moving a little rough. I soaked some 1000 grit sandpaper in atf and deburred the valve. it moves freely now. but nothing changed.

I checked the pressure regulator valve and the boost valve. Everything seems allright. Stock spring, no additional washers. Just the horseshoe and the 4-tang washer.

I checked the detent valve. It works fine.

I checked the filter, the tube and the O-rings.

The governor works, has stock weights and springs. The valve opens according to the specs in my ASTG manual.

Fluid is ok.

No shift-kit installed. The feed holes in the plate have been drilled to .125'' according to the crankshaft coalition wiki. thats the only modification.

What else can cause a tranny not to shift in 3rd gear (strong reverse, good 1-2 shifts) and make it whine like crazy? Unfortunately I couldnīt get a pressure gauge that reads 300-400psi up to now, but it has over 120psi in park at idle.
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Old 07-13-2011, 01:51 PM
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How did you get on, proplem resolved or not?
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Old 07-14-2011, 10:29 PM
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pump

how did you align pump when rebiult
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