Rear End Pressure
 

Planojc mentioned in another thread about "venting problems due to the short torque tube on the Mitchell".

I experienced this also after I installed the Mitchell. It appears with the Mitchell in the torque tube the rear end has no where too vent (unless your seals leak). My rear end started leaking oil out the top banjo bolts where my Panhard bar attaches.

I installed a vent and has been working fine for ~2 years.

Just something to be aware of when you install an O/D in the torque tube.

https://www.fordbarn.com/forum/attac...7&d=1686777506

Re: Rear End Pressure
 

Where did you find the vent?

Re: Rear End Pressure
 

Why couldn’t you drill the torque tube up by the overdrive tap it with 1/4 inch pipe thread and a hose barb and vent it up there? You wouldn’t really see it. Just a thought.

Re: Rear End Pressure
 

The vent I used is similar to this. It closes so water/moisture or dirt can not enter. https://www.amazon.com/Alemite-30481...009K4ZVQ0&th=1

No reason you can't. I would still use the one way vent as above. ¼" PTF is a little large, the one I used is ⅛" PTF. It is a lot less noticeable that a spot of Meropa on my driveway.

Re: Rear End Pressure
 

I am gathering parts for a Laycock OD custom build - somewhat similar to the Mitchell. It really didn't appear to me that the rear end needs venting - I'll make sure to incorporate a proper vent. Thanks for drawing attention to this! :)


Is the pressure from thermal expansion/contraction - or is there something else at stake also? :confused:

Re: Rear End Pressure
 

I first had this problem on a 39 Coupe after I installed a Mitchell and after venting the banjo at the axle housing, my leak went away. I think Ford started venting all rear ends when they went to an open driveshaft. I know my 50 ford was vented like the one Y Blockhead has installed.

Re: Rear End Pressure
 

Here you all go again....giving me another thing I have to do! Just ordered the part suggested by Y-Blockhead. Thanks for the tip.....this is why I love this place!

Re: Rear End Pressure
 

Just checked my Mitchell and the unit has a vent tube. Why isn't this sufficient?
Is it because it is too far from the banjo?

Re: Rear End Pressure
 

Re: Rear End Pressure
 

Thanks for the info.

Re: Rear End Pressure
 

This is a very interesting post. I have wondered about the axle housings and banjo having the ability to handle any pressure build up when a Mitchell overdrive is installed.

Our BLT GUYS organization here is Southern California has installed 18 Mitchell overdrives in the past three years and have not had any reported oil leakage from the axle housing area itself.

The vent valve from Amazon looks like a good idea. However, my concern is installing one during a Mitchell installation. Drilling and tapping the hole may introduce metal chips into the housing.

If the installation takes place at the time of a differential overhaul, there would be no problem as the metal chips can be easily cleaned out.

Has there been any reports of the valve blowing oil over the axle housing?

Tom Endy

Re: Rear End Pressure
 

Hi Tom. When I first notice the leak, I never dreamed t was because of the Mitchell. Thinking it was the banjo bolts, I installed copper washer and sealant on all the banjo bolts, like on a Ford 9" rear end.

When it continued to leak I figured the rear end needed a vent. Being slick, I drilled one of the top banjo bolts and silver soldered a tube onto it, added some clear tubing and a one way valve. I routed it up to where the Mitchell vent was located. (see picture). BIG MISTAKE!! It blew oil all over the place!!

So I added the one way valve to the axle tube as it is on the (" in my '55 Ranchwagon. It works great, never a drop out of the valve.

When I drilled the hole for the one way valve, I slathered the drill bit with grease. Same on the tap and took it slow. I stuck a magnet in the hole after and did not get any chips. I am as confident as I can be that I didn't get any metal chips in there.

I have done a few others (not nearly as many as you) with no issues. You can see in my picture in post #2 that there is no oil residue.

Maybe others don't have oil leaking because of pressure buildup?? I don't know.



https://www.fordbarn.com/forum/attac...0&d=1686856744

Re: Rear End Pressure
 

Does Mitchell offer any advice on this.

I mean, the horse might be willing to share some information. (from the horses mouth)

I have a rearend to be rebuilt aith Mitchell and don't want to start guessing.

John

Re: Rear End Pressure
 

I don't know. I never thought much about it until I saw another person mention it the other day. I just vented mine and called it a day. No more leakage. I did all this ~2 years ago.

If your rear end isn't leaking, maybe you don't have to vent it. I just know the Ol' Girl started messing herself soon after installation of the Mitchell and stopped when I relieved her....