My tranny makes noise... your diagnosis needed

dslhtrdr

dslhtrdr

Always learning...
Joined
Sep 2, 2009
Messages
677
The 47rh in my '94 12v is making some noise. This noise can best be described as a buzzing sound. It only does it when it's cold, and really bad in reverse. It can be slightly heard in park, and when in drive it does it right about 1200 rpm's. Once it has warmed up to a little over 100* on my trans temp gauge, it goes away.

I have stalled my truck with the tc locked 2 times. Once on the street, and once during a sled pull. It started gradually making this noise since that happened, but I don't think it's the tc. If it was, I think it would be making the sound all the time.

I've filmed a video of it making this noise, but because of the sound of my truck running and crappy sound quality of the camera it can't be heard.

I had a well known and reputable tranny guy who has had his hands on quite a few well built trannys flush and replace the fluid, mostly because he said that he's seen them make this buzzing noise from the filter being plugged. He dropped the pan and everything was spotless and the filter was practically perfect. Changed the fluid, and it's still making the noise.

So in doing some research I have found that sonnax makes a "no buzz pressure regulator valve" for these trannys. I believe that this is my problem but I want to here from you guys to get your opinions and personal experience.

Bring on the ideas gentlemen!
 
Also, forgot to mention that when it's making this noise, the driving characteristics of the truck are unchanged. It has no affect on drivability whatsoever. I can't feel it coming through the seat, pedals, floor, steering wheel, etc. It's just really friggin annoying. I would also hate to ignore it for so long that it would ruin something else in in the tranny. It wasn't cheap.
 
Do you have a pressure gauge handy? For a built tranny, you need a 0-200 psi gauge. Hook it up to the middle port on the passenger side and go for a drive. See what the gauge reads when the tranny is making the noise.

Then, after the fluid is warmed up, see what the gauge reads at the same rpm/gear etc where it used to buzz.

Does the noise sound similar to the whine of a power steering pump when the fluid is cold and the wheel is cranked hard?


From what you've described thus far, if the pressure checks out ok (not low), I wouldn't worry about the apparent cold fluid whine.
 
No pressure gauge in my possession at the moment. When I had the fluid flushed and filter changed, he said everything looked perfect. I believe he did check the line pressure and said it was great.

Are you talking about an electronic pressure gauge? Running the wires into the cab to the gauge or a mechanical gauge? Does the pressure remain the same at idle as during a drive (under load, different amounts of throttle)? I thought that the pressure rises as rpm rises. I'm brave but not brave enough to hang on underneath the truck and read the gauge while it's moving LOL

The sound does not compare to a power steering pump whine unfortunately.

I know that stalling the truck with the tc locked up isn't good for the tranny but am unsure of what can possibly be damaged when it happens. I'm still leaning towards the pressure regulator valve as the cause of the noise at this point.

Thanks for the reply! Keep them coming
 
I have a mechanical gauge in my truck, very handy!

100_0051.jpg
 
YOUNG GUNS15 said:
I have a mechanical gauge in my truck, very handy!

100_0051.jpg
Click to expand...

Hmmm... That gives me some ideas. I'm assuming that a 0-400psi gauge like that can be found at a hydraulic shop. Can a gauge like that be universal, like for air and/or fluid?
 
You could just get one for a hydraulic system, pretty much what a auto tranny is anyhow. Not sure how a guage designed for air would work out
 
I was thinking that a gauge like that should be used just for measuring fluid pressure.

Some folks aren't too comfy with having oil being pumped through a line into the cab for a gauge. I don't really see what all the fuss is about. As long as you make sure your connections are good there's not much to worry about. I'll have to go to the local hydraulic shop and see what they have.
 
Yep, just a hydraulic shop across the state line in colorado! i think it was 15-20 bucks, i dont mind the line coming in the cab, the only fuss is it interferes with the 4x4 shifter and its not lighted, i might convert to a electric to save space. But i love the look of this 400psi gauge just chillin there. Gives an old school look i think
 
Couldn't make it down to the hydraulic shop over the weekend :doh:

Now that the weather is warmer the buzzing noise isn't as bad and goes away much quicker. I still want to get a gauge hooked up so I can monitor what the pressure is like though.
 
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