727 question.......

[Tarrbabe]

Yes I rebuild my own but sometimes you like a little help knowing what to look for.
Just bought an 80 Stepside. When first started there is a noise that is best described as a buzzing or whinning type noise. After several minutes the noise go's away. Sound changes when gears are changed, thus it is the trans.
Pump? TC?
Any input on this? The trans seem to work fine except for a miss-adjustment of the kick-down (shifts too early). I'm sure that is due to removing the Edelbrock and replacing it with a stock 2 bbl.
I didn't notice this noise when I bought it because the clutch on the fan was making so much noise. I knew that sound really quick but couldn't hear the other.

Thanks.......

[pcrmike]

Probably a planetary set. It runs both planetarys in first. :-) PCRMike

[mopar413]

Tarbabe; if the trans has not been serviced, try that.I had one do that and it was the pump.The filter was partly plugged, restricting the flow of fluid into the pump. Hope this helps........Ron

[Tarrbabe]

The guy I bought it from said the noise started right after his son put a shift kit in it. I still thought it was the clutch fan as that was all I could hear.

[John Kunkel]

A whining, buzzing, moaning noise (especially when cold) is caused by a rapidly cycling pressure regulator valve.

This has been the subject of several TSB's over the years, it is mostly just an annoyance, not a real problem.

The factory recommended repair is to replace the valve body.

[Tarrbabe]

but it seems excessive to replace the valve body when de-burring and a new spring should fix it. But then where would you get a new spring?
This noise started right after the guy put a shift kit in it. Wonder what he did? Throw the old valve body out and the shift kit too I guess.

[John Kunkel]

Shift kits raise the line pressure, this makes the pressure regulator work extra hard when the fluid is cold and thick; instead of slowly modulating it can go through a rapid cycle of opening and closing.

I wouldn't assume that deburring and a new spring would stop the buzz, depending on the kit installed it might have a new spring (some kits include a spring for the PR).