My trans is locked up. As soon as I put it in gear, if I don't give it gas to let it take off (and it wants to take off) it'll snub. Previous owner replaced the trans and nobody can tell me what one it is (dealership was useless). I've been told what's supposed to be in there. It's not tho'. I know at least that it's a 500.

Tranny info is like pulling teeth. Here's what I've found so far. Hopefully it's accurate. I've been told by most that 92 is 92 specific. I attribute this to it being the first year of the magnum. I've been told by a reputable trans shop that 88-91 will work but are lighter duty. 93? don't know. One place said 92-93 are the same. More said it wasn't. 94-96 don't know.

Elsewhere I've read of 500 to 518 swaps and that they're a perfect swap sizewise. (Provided it's not a diesel)(Also internal-external balancing differences on 360 versus anything smaller) I've read one place that ma-mopar went cheap and 1st shift gearing is the same on all trannies. Yet, I've also read that this is not the case; that the 3.9 is indeed a different gearing from anything larger. As you can see there is a lot of contradicting info. Hopefully what I've scraped up is accurate and helpful. If someone knows different, please feel free to correct this.

I know of a cheap salvage yard. I can get 500 & 518 trans there for the same price. Can anybody clarify this issue? Has anybody done this swap?

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92 3.9 4x2 ext cab automatic

The 500 and the 518 are not direct swaps. The 518 is longer and has the heavy 727 core .The trans are made for any one engine size. The 500 is for light applications and that is why it is behind the 6cyl. The gears are the same from year to year. But they will shift a little different depending on what it came out of. Sad but dealers are good at shrugging their shoulders and saying I don't know,bring it in and we will fix it .

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88 2.2 5SP
95 5.2 Mag
A518
8 1/4
Electronic ignition
Custom EFI (megasquirt 2.2)

The 500 and 518 are a little different in size but the a 500 rebuild kit is a 500 rebuild kit, likewise a 518 rebuild kit is a 518 rebuild kit, they fit pretty much regardless of year, 92 and 93 trans should interchange as long as they are the same model. 94 and newer have more electronic sensors on the valve body.