BarryA Posted April 27, 2010 Report Share Posted April 27, 2010 Need more "freeway-friendly" gearing in the 620 KC - before going to the effort to pull a diff center section out of an auto trans 720, is the info that a search turned up correct that 620 and 720 diff carriers interchange, and that 2 wheel drive automatic trans 720’s normally came with 3.90:1 differential gearing? Quote Link to comment
Z-train Posted April 27, 2010 Report Share Posted April 27, 2010 Actually it's a 3.89.There will be a fender tag calling out the ratio on the bottom of the tag.If you find two of them,stuff one in an envelope and mail it to me-thanks. :blink: Quote Link to comment
BarryA Posted April 27, 2010 Author Report Share Posted April 27, 2010 Actually it's a 3.89.There will be a fender tag calling out the ratio on the bottom of the tag.If you find two of them,stuff one in an envelope and mail it to me-thanks. :blink: Forgot about the tag - assume it should be on one of the bolts holding the diff carrier into the axle housing? Automatics turn up in the yards around here periodically - if I run across another 3.89 tag I'll be happy to pull it and send it along...... Quote Link to comment
Z-train Posted May 1, 2010 Report Share Posted May 1, 2010 No-it's on the drivers side inner fender(fenderwell).I was just kidding,but if you do find one....... ;) Quote Link to comment
datzenmike Posted May 1, 2010 Report Share Posted May 1, 2010 pass side inner fender below the hood hings. Near bottom TRANS/AXLE:... FS5W71B.... HF38. 38 means 3.889. 41 is 4.11, 43 is 4.375 and so on ... good hunting. Avoid the 4X4s because the drive shaft flange changed in around '82? Go with 2wd. Quote Link to comment
BarryA Posted May 11, 2010 Author Report Share Posted May 11, 2010 No-it's on the drivers side inner fender(fenderwell).I was just kidding,but if you do find one....... ;) This one was on the passenger's side, near the hood hinge - I popped the tag off, but I don't need it. Be happy to drop it in an envelope and send it your way if you want it - just PM me an address......... Quote Link to comment
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