TH400 whining

[BAD1916]

Thought I’d post this up before I yank my trans...
I have a 71 GMC 2500 454(original 402 block was cracked) with a TH400 from a 67 chevelle( don’t know if that matters any). This setup has been running for 4 years and this Is my normal driver. Anyhow, a few weeks ago I left my house and I could hear the trans whining so I pulled over and put it in park. I didn’t hear anything while in park so when I shifted back to drive the noise was gone. I assumed it was a fluke. Fast forward a few weeks and this morning me and my boy are headed out to go fishing, got the kayaks all loaded up and while enroute the whining started again but this time it didn’t stop. I tuned around to head home and when I got stopped at a light the Burb would hardly move. So called AAA and got tow hooks instead of fishing hooks. At home the truck seems to shift fine and goes in and out of gear fine though I have only moved parking spots.Sorry for the long winded post and if you’ve read this far do you have any thoughts on anything to look at before I pull this thing out? Thanks in advance for any help.
Bryce

[BAD1916]

Forgot to mention fluid level is good and no burnt smell. I also checked the vacuum modulator connections and all is connections are good there.

[HO455]

You might try replacing the filter. It has never worked for me but you might get lucky. Not trying to be funny just stating the facts. Plus once the pan is off you might see something that could be fixed. Like loose bolts in the valve body.
After replacing/rebuilding a TH400 every 18-24 months in my GTO for 12 or more years in my experience once they start slipping too much to move the vehicle they are toast. They might work for a little while when cold but once they warm up your stranded.
Best of luck to you.

[BAD1916]

Thanks for the info. That is kind of what I figured but I thought I’d get some thoughts from people with more experience than myself. I will drop the pan and see what it looks like. The filter was replaced less than 10000 miles ago but wouldn’t hurt to try.

[WorkinLonghorn]

Loose pick-up tube causing air to enter causing whine and low pressure screwing up engagement?

[BAD1916]

When I pull the pan I will look for that. Thanks for the suggestion.
Bryce

[clinebarger]

I've seen more than a few Felt style TH400 filters stop up, Alto sells a Stainless & a Brass screen type filter.

[vince1]

I went through an old Borg Warner T-35 and found .030" radial play in one of the planetary bushings. I would think that transmission must have really whined.

Sudden onset though of a noise like that must be something different.

[b454rat]

whine is prolly the pump. I had one do that, after awhile it wouldn't move when cold, once warmed up was fine. I believe it had a shift kit, and would chirp the tires lol. But then one day outta the blue, it quit. Like a light switch quit, got on the gas would go, left off to coast, got on it, nothing....

[BAD1916]

I forgot to update this. After talking to the trans shop I decided to yank the trans and drop it off and figured that if everything was good it would at least get resealed and quit leaking. He said the high gear clutches were bad. While it was out I did a cam swap, so with the trans shifting right and a bit more power the Suburban is way more fun to drive. 😎Thanks all for the suggestions and input and hope everyone has a great Labor Day weekend.
Bryce