Transmission Help - Which one to go with for my E38 750il V12 5HP-30?

[PiperBMWe38]

Hi all,

I'll try to keep this brief. I'd love some opinions on what to do...

Was dealing with transmission issue on my 2001 750il V12 where it would throw the trans fail safe error when downshifting from 5th gear to 4th under load (going up hill, etc...). I replaced torque converter, which 2 places had diagnosed as the issue. That wasn't it. Then I replaced the valve body. That wasn't it. However during that replacement the mechanic found an abnormal amount of metal shavings... boom new transmission needed, no way around it. I was hoping this wasn't the case, I was't surprised.

I found one on eBay that was listed as follows "JDM BMW 95-01 BMW 750 E31 V12 5.4L ZF 5HP30 Automatic Transmission Low Mileage." I inquired about the miles and the seller said it came from a BMW that was in Japan with 55k miles on it, as he only imports low mileage transmissions from Japan. He said Japan and EuroSpec, and U.S. Spec cars can all use the same transmission. The seller had good feedback rating on eBay. I noticed he said both E31 and 750i, which doesn't add up, but after talking with a few sources, I was told as long as it's a 5HP-30 Trans, it should fit my car. So I pulled the trigger. Photos below...
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more story below...

[PiperBMWe38]

3 Days later the seller says he can't find the transmission in his warehouse, and offers me another one, which looks nowhere near as clean, however it doesn't look terrible either. I asked him about the miles and what model it came from, and he just said all his transmissions are low mileage and this one was from a 1998 BMW, and similar miles. He didn't say what model...
Here are those photos for that one. I have not yet agreed to purchase this one...
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Again, it's not as clean, it doesn't have the Torque Converter, but I have a new one of those anyway for $1,000 already, but something about this whole experience is already rubbing me wrong. I have no idea what model or year this came off of, and even less of an idea on what the miles are. I was already taking him at his word that the prior transmission had only 55k miles on it. I don't think there's a way to tell.

Here's my last thought (below...)

[PiperBMWe38]

There was a transmission I almost bought that is from a 2003 Aston Martin that had under 20k miles on it. The reason I didn't buy it is the transmission has cracks to the back of the housing that need to be soldered, or the case needs to be replaced. The damage looks really minor, and I asked my mechanic and he said he can switch the case/housing from my old transmission no problem, and he recommends I get this one instead, but I'm wary of the cracks in the first place, was it just dropped, is that from an accident, is the trans toast, etc...

...and also if an Aston Martin V12 5HP-30 Trans can really be swapped to a BMW 750il. Are they really the same transmission? They do both say 5HP-30 on the tag.

Any thoughts? This trans does look pretty darn clean, and the damage is very minimal...
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[XAlt]

Even between the V8 and V12, the 5HP30s have some distinct differences, I don't think the Aston one would work properly. Removing the bellhousing also takes quite a few other parts with it.

[kouks]

Even though the core of any transmission is used in different vehicle and is the same, the electronics and in some cases the torque converters can be different. In some cases the external mounting hardware is different. This is why you’ll see a trans part number the same across vehicles, except the last three or four numbers are different, like -xxxx. Those last digits explain the model type of the specific trans.

You need to have the entire part number for your trans and get that one specifically for your car to swap it out. If you buy one with a different model, it will be up to you to figure out the electronics, valve body and torque converter required to match it to your car.

[PiperBMWe38]

Got it, thank you for the replies! I found a ZF 5HP-30 Transmission Part Chart for anyone else that follows my path on this...
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