Hissing sound coming from overdrive

[47heaven]

Thought I'd post this to see if I could get some diagnosis on here. For the past month I have had a hissing sound, what I thought was coming from clutch, but turns out to be coming from the overdrive, from what I can tell. It's a "come and go" type of thing that seems to be heard when slowing down in 3rd or 2nd gear. The overdrive seems to be working fine, with the exception of it not engauging right away on occasion.

My question is if anyone on here with an overdrive (I have the Borg Warner R-10 model) has had this type of experience with their overdrive and can tell me what that sound my be indicating. I've taken it down to the mechanic, but of course the sound won't show up when I take him around the block...go figure.

[Normspeed]

Hi Darin, long time no see. That one has me stumped. Not much in there that would hiss. Does it do that with the od handle in or out? If out, I would check for a loose carburetor. Using engine for deceleration increases vacuum and can cause a hiss at a leaky carb flange gasket. A long shot for sure...

[James_Douglas]

If it is in fact in the OD unit then it may be a bearing that makes noise when it is unloaded.

As Norm said, you need to do more testing:

Does it make the noise in 2nd and 3rd OVERDRIVE with the OD locked to the engine?

Does it make the noise when the unit is freewheeling in 2nd and 3rd but below the cut-in speed and still with the OD in circuit but not actuated?

Does it do it with the cable pulled out -no OD ?

Does it only do it when no torque is being applied?

With a little more information we can help run it down.

James

[BobT-47P15]

There's not an opossum hiding up on top of the overdrive tranny, is there?

[Don Coatney]

Can you controll this "hiss" (make it come and go) with your accelerator? If so it may be a differential issue not a transmission issue. I thought I had a transmission noise so I bought and installed a replacement transmission. The noise was still there with the replacement transmission. My noise is coming from my differential. You may have the same issue. Follow the advice James gave you and do more testing.

[47heaven]

Ok, guys. I'll print this advice and test her out tomorrow. I wish it was constant so I could pinpoint it better. I'll be back later with the results of what I found out. Thanks, again!

[Dodgeb4ya]

Make sure both sides of the OD trans is full of oil!

[Reg Evans]

There's not an opossum hiding up on top of the overdrive tranny, is there?

If it's a really loud hissing check your vindshield vipers too

[47heaven]

Well, I guess I may have had the hissing sound mystery solved, but only after having my exhaust leak repaired. A few weeks back, when I first posted this thread, I had taken my car over to Bob Amos to show him and see if he might have known what was causing the strange sound. Bob did notice that there was a major vacumn/exhaust leak coming from in between the intake and exhaust manifold right below the carburator. Took it to my mechanic and told him about the leak and he also noticed the big exhaust leak coming from where the heat riser was. Long story short, had the leak fixed and the the whole plugged up where the heat riser was and now I seem to have better performance, not to mention less bogging down in thrid gear. The hissing sound hasn't shown up, yet. So hopefully that took care of it. Still have a little rough idling, but I guess that could just be a carb adjustment.