U-Haul Trans Pan Drain Bolt Size

Posted by: wrenchrat

U-Haul Trans Pan Drain Bolt Size - 05/03/21 11:55 AM

I managed to score a genuine Ford U-Haul trans pan for the AODE/4R70/4R75 transmissions. I'm trying to figure out what threading is used for the drain plug, as I'm going to be installing a Fumoto valve on the pan to make tranny fluid changes easier. I already use one of these valves on my engine oil pan and it works great.

Does anyone know what the thread pattern is on the drain plug used in Ford U-Haul pans?
Posted by: CrystalPistol

Re: U-Haul Trans Pan Drain Bolt Size - 05/03/21 12:58 PM

How often do you do them?
Do you want a valve hanging down as the lowest point of the car?
I don't know the thread for that pan, but seems I read it was 1/2-20, but I could be wrong. Could be metric. I'd be inclined to take the clean pan to about any hardware store or automotive parts store and use their thread gauge to be sure. I do know that I used that thread for my self installs.
Posted by: wrenchrat

Re: U-Haul Trans Pan Drain Bolt Size - 05/03/21 02:03 PM

I change the trans fluid every 20-30k miles in a 3 part sequence. First, I drop the pan and change the filter. Then I fill it up, drive the car a bit and drain the pan again. I do this twice in addition to the initial drain and fill to complete a full fluid exchange. I don't like using the cooler lines to change the fluid, I prefer just draining the pan.

Clearance-wise, I'm not terribly concerned. The Fumoto valve is low profile and I haven't had an issue with it on the engine oil pan. The U-Haul pan has the drain plug facing backwards on the pan, unlike the dorman one which (stupidly) is facing forwards.
Posted by: CrystalPistol

Re: U-Haul Trans Pan Drain Bolt Size - 05/03/21 10:29 PM

OH, I see. I put my 1/2-20 tapped plate in the same place as the U-haul pan does, rear face of the "well" area. To install it, I drill and tap qa 1/2-20 hole in a strip of 1/8" steel that is maybe 2 " long, 1" wide. I drill a 1/4" hole near each end, and I weld a 1/2-20 nut to the piece with a bolt in place to align my threads, then I run a tap through to clean the threads. I use a couple 1/4-20 bolts and nuts to bolt the plate into the pan like where the U-haul pan has welds, takes three hole in the pan. Then after install, I pien the small bolts after installing nuts good so there no loosening, and I use a standard 1/2-20 drain plug & washer. In the 2001, I put it opposite the magnet though, don't know why I did that though. It works OK so I leave it alone. My '01 has a TC drain too.
We put one in my '06 CVPI as it did not come with TC drain. Seams to me, with both drains, and after fluid change, it takes near 12 quarts to refill. AFAIK before 2001 they had the TC drain, 2002 & up did not, but 2001 can go either way.
Posted by: wrenchrat

Re: U-Haul Trans Pan Drain Bolt Size - 05/06/21 02:08 PM

Yeah I'll have to take the pan over to the parts store to figure out what threading it is. I currently have a Dorman version of this pan that is already starting to rust pretty badly after just a few years of Michigan winters and the u-haul pan has a lot better quality of finish on it which is why I wanna make the switch.

Just curious, what do you recommend for drain plug washers for the Dorman pan? I've been reusing the same washer but I know I need to replace it if I end up using this pan while trying to figure out what I wanna do with the u-haul one.
Posted by: CrystalPistol

Re: U-Haul Trans Pan Drain Bolt Size - 05/06/21 05:45 PM

I've used those plastic ones before, but I had one crack and leak, so no more.

I've used those aluminum ones with the molded O-ring of rubber inside the aluminum ... and just plain copper ones too. Then, there are some drain plugs with a groove intended for an O-ring but I can never find a new O-ring handy ... I have a box of them somewhere but if the O-ring is too fat, it'll get damaged.

I like the ones I mentioned that have the O-ring molded inside a aluminum ring that limits compression of the O-ring, and the copper ones are good as they can be reused after heating them really hot with propane, then quenching in water which softens the copper.

I've seen soft aluminum washers, but only used them on a Gold Wing MC oil drain, I guess they'd be OK. I don't know how I'd soften them for reuse though.
Posted by: wrenchrat

Re: U-Haul Trans Pan Drain Bolt Size - 05/06/21 11:13 PM

Interesting. I hadn't thought about the copper ones, I've only used them for brake calipers before. I'll have to look into those and the ones with the rubber gasket inside the metal washer. Thanks for the insight!