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WTB 3N71B automatic transmission


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the transmission is not motor specific so much.  As vehicle specific.  Some are floor shift, some are column shift.  You have a 620, so its a floord shift.  Datzenmike knows what transmissions you can replace this one with....

 

Now flex plates and such, theres a little more to those then just that.

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I have a floor shift auto that came out of 72 510 wagon with L16. Im in Upland,Ca not too far from you. I got this from a friend parting out a 510 wagon and Im not going to use anytime soon so if this will work I would like $100.

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All 3N71B automatics are floor shift (well maybe column shift for two months on the '71 510 when they switched from the BW 35 to the new JATCO 3N71B) otherwise floor.

 

The 510 3N71B is about 26" long.... most if not all others are longer at 31.5". Your 620 will be a long tail.

 

From '71 to about '81 all L series 3N71B automatics are similar enough to swap even the Z car six cylinder ones, with the exception of the turbo zx auto. It likely has a different spline count for the driveshaft. Around '82 a locking torque converter was introduced and this not only uses a diferently torque converter but a differently shapped 6 bolt flex plate to fit it.

 

L16s and L18s use a 5 bolt flex plate. You could use a later auto of any year (up to '81) but you will need the 5 bolt flex plate.

 

There may be differences internally between car and truck L20B automatics or perhaps between 4 and 6 cylinder autos. One thing is for sure the turbo auto has several more discs and clutch plates inside, stiffer springs and a modified modulator valve to handle the extra power of the turbo. The 620 truck may have extra also to make it more 'heavy duty' but I don't know. There may be very minor linkage differences and possibly electrical plug shapes between models. Nothing that can't be fixed.

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