chester Posted March 17, 2012 Report Share Posted March 17, 2012 So I just bought this and was wanting to make sure it will work for my ka swap that I am trying to do in my 77 620. As the title says it's from a 85 720 2wd, and is the same length as the tranny I have now. Also any and all info about what the gearing could be would be nice. Thanks Dan Quote Link to comment
datzenmike Posted March 17, 2012 Report Share Posted March 17, 2012 Yes it will fit the Z and the KA series engines. Yes it will fit and work in your '77 (even the speedometer cable will work.) You need to remove your '77 speedo cog and instal in the 720 case to keep your speedo accurate because the 720s used different differential gear ratios. BUT..... You will have to make a simple modification to the speedo pinion before you do. Get a small angle grinder and a $4 metal cutting blade. On the side of the pinion just below the threads is a small slot that the keeper fits into and the 10mm bolt holds in place. Long story short... the 620cog has the slot 180 degrees around on the wrong side for it to work in the 720 case. Not the end of the world, you'll just nick a new slot on the 620 pinion and it will fit just fine. I did this with muy 5 speed instal into my 710. Been to Canby and back with the 'upside down cog' no problem. So just use the angle grinder to make a new notch 180 degrees around on the opposite side so the key will fit and push in place and bolt down. Should look similar to this one... Don't over think it, this isn't rocket science. :lol: This will keep the 620 cog and 620 differential relationship and the speedometer will stay accurate. Quote Link to comment
chester Posted March 17, 2012 Author Report Share Posted March 17, 2012 thanks Mike. I thought it would work but wasnt 100% sure. As of now my speedo is off. I have a 4.37 speedo gear drive but have 4.11 rear end. Now I should have a correct speedo when I get it in. Mike you wouldnt happen to know what the gearing could be, or the best way to check myself? Quote Link to comment
datzenmike Posted March 17, 2012 Report Share Posted March 17, 2012 Friggin' slow connection... The '85 should have the same internal gearing as the '77-'78 620 truck so you're good. The '85 2wd could have had a 3.545 or a 3.889. NOT a 4.11 Quote Link to comment
chester Posted March 17, 2012 Author Report Share Posted March 17, 2012 Right on Thats good news. Thanks Quote Link to comment
wayno Posted March 17, 2012 Report Share Posted March 17, 2012 If you doing a KA swap, you could just run the gearing it had in the stock vehicle the KA came out of, 350s or 390s, the engine can handle it. The tranny might even have the correct speedo cog in it. Quote Link to comment
chester Posted March 17, 2012 Author Report Share Posted March 17, 2012 If I had a donor rig, I would. I would like to get some 3.90s after I do the swap. to see if I like them better then the 4.11s that I have now. Who knows I might even go with 3.70s Quote Link to comment
elmerfudpucker Posted March 17, 2012 Report Share Posted March 17, 2012 the higher the number more power lower number means more speed right? or do I have it ass backwards again??? Quote Link to comment
datzenmike Posted March 17, 2012 Report Share Posted March 17, 2012 A 3.364 would have a higher top speed than a 4.375. Quote Link to comment
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