Why does my TH400 make noise for 5 secs when I start the motor in the morning?

I thought everything was perfect with this tranny since I rebuilt it but the last couple times I started the car I noticed this. It a whirring sound like there is air in the oil pump, and goes away after about 5 seconds when I start the car only after sitting overnight. The fluid level is full, and I even tried adding a few extra ounces and it still does it. I switched to the newer ('68 & up) style filter and pick up tube with the newer style pan.......I'm wondering if that has something to do with it?

I hope it isn't dirt in that converter check valve in the oil pump ou:

 

After removing the pan and checking things over, I think I found the problem.....it was the filter pickup tube. Acting on a performance tip from a freind, :error: I used 2 "O" rings on it where it fits into the transmission case as opposed to 1, and it must have been pushing the tube out too far causing it to suck air in somehow. I just got it back together with 1 "O" ring and the noise seems to be completely gone. I'll know for sure tomorrow morning when I start her up after sitting overnight. :bglasses:

 

TTT......tried it this morning and I've still got the same problem o No:

 

Anybody?

 

The 2 o-rings will not cause a problem. Usually a whine is caused by sucking air or can also be caused by a bearing in the converter. You may want to hook up a pressure gauge and watch the pressure gauge when you fire it up. Jim Burek

 

Chipmunks?

I really have no clue, but since it happens after sitting overnight, I'd guess fluid was draining somewhere. Maybe the converter isn't holding the fluid like it should?

 

That's the same converter I had in my old tranny and it never did that. Maybe I just never noticed it before, but while driving it around yesterday, I noticed that if I leave it in L2, when I slowly rev it up over 3,000 RPM I hear it start to whine. Otherwise it's perfectly quiet except at startup. Does that sound like a converter bearing?

I'll see if I have a pressure guage that will fit. otherwise I'm going to try changing the filter first, and if it still does it I may have to try another converter. :bglasses:

 

IT'S FIXED! YAHOO!! :beer

Went out this morning and presto.......noise gone! :beer The problem was the newer style filter was somehow allowing the converter to drainback overnight. I put the original style PF-160 filter and pan back on yesterday, and the noise while revving high in L2 is gone also! The only thing I can think of is that the later style filter was too restrictive to flow with the paper element. The OE style AC filter I'm now using prolly has a screen in it.

I should also note that when I checked the fluid yesterday morning before starting it, I noticed the fluid level creeped up the dipstick overnight about 2 or 3 inches. It made the noise when I started it. Then yesterday I switched filters, and I checked the fluid again this morning before starting it and it did not creep up so high, just about 1 inch above the full mark. This tells me the converter did not drain back with the original style filter. I think that's why the noise is gone. Incidently, I purchased the defective filter from Autobone. :af:

Phew.......what a relief! ou:

 

Cool - and thanx for the follow-up.

 

I feel bad for the person who has problems like these and lacks the knowlege and determination to find the cause. Sometimes a systematic approach is the only way, short of just replacing the whole thing with a new one. Nothing is more satisfying to me than to know "why". I'm always glad to pass on my experiences to others.

I remember back a few years when I had a minor power steering noise that only appeared when hot and it took 3 or 4 different pumps and a rebuilt steering box before I figured out it was the fluid. Our older cars were designed for "type A" transmission fluid to be used in the power steering. The modern dexron III garbage or clear power steering fluid doesn't work well in place of that in older power steering units. When I flushed everything out and put in synthetic trans fluid in there my power steering is perfectly quiet and even works smoother. You won't read that in a book or hear it from a modern day mechanic. Sometimes complicated problems can be caused by something so simple it's almost unbelievable. :bglasses: