A-999 behind a 340

6T9 V-100 said

I have the 340 sitting in the shed, so it isn't worth the hassle of selling and then going and getting a 360. My biggest concern is the lock-up feature of the tranny- how will it act and hold up behind a decently-built 340? Never built a Mopar w/this feature and I've heard that this tranny don't like a decent power level.

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Lockup was for economy. Lockup 999's were found behind trucks, vans and Diplomats. Think cop/fleet vehicles and old people pseudo luxo barges. Lots of torque at a low rpm, probably never saw the high side 4K. Most 999 variants had a 4 or 5 disc forward clutch pack and later ones had the low gear set but most of those were lockup transmissions.

Drag racers use the 904 because there is less rotating mass. You don't hear about 904's blowing up like 727's do. The MP Chassis book says it's the quickest trans to have in non-lockup form.

Some people try to piece together a 999 by retrofitting desirable later parts into an older 904 case. There's a lot of variations in the models over the years, you really need to know what to look for. Most of it is pretty hard to find too.

Like anything else, it will probably hold up just fine unless you do a poor job assembling it or abuse the crap out of it.

Just put it in and report back to us if you blow it up.