budsaipan Posted September 20, 2009 Report Share Posted September 20, 2009 I have a 77 5 speed that's going into my 79. I believe the 79 came wit 4.11. I do have a 77 long bed parts truck so would it be better to use the gears of the 77 or keep the 79? :mellow: Quote Link to comment
ggzilla Posted September 20, 2009 Report Share Posted September 20, 2009 Best would be the steeper gearing. Quote Link to comment
datzenmike Posted September 20, 2009 Report Share Posted September 20, 2009 (edited) Better depends what you want. What's better for you? Mileage: Assuming you are keeping the 4.11 in your '79 then either tranny will give about the same mileage at least on the highway in 5th gear. Performance: The '79 tranny has a 'wide ratio' gear set with a much lower 1st, 2nd and 3rd in it to compensate for the extra effort to move the truck with the lower 4.11s in it. First gear is a nice 3.592 to one, making take offs much easier. The '77 tranny is a 'closer ratio' with a lower 3.321 1st gear, so take offs will be a bit more of an effort with the 4.11s. Acceleration will be slightly sluggish with this tranny. I would install the '77 5spd and see how you like it. The '77 tranny will have the correct speedo cog for the '77s 4.375 ratio rear end so use the '79 cog to keep the speedometer accurate for the 4.11s. If you can live with it, all and good, but if you find it sluggish and want it back the way it was, simply swap the '77s 4.375 rear end gears into the '79 truck. To keep the speedometer accurate keep the '77 speedo cog in the '77 tranny to match the 4.375 gears. Confused? Edited September 20, 2009 by datzenmike Quote Link to comment
budsaipan Posted September 20, 2009 Author Report Share Posted September 20, 2009 Oops wrong section. anyway, thanks for the tips. I guess I'll have to go with the 77 rear end. I'm not sure why anyone would want to have the sluggish feel in the first place. Sorry for my ignorance on the gearing but what if I had to put some lower gearing than 4.11? say 3.x gears? then what would happen? I'd like a good setup where I'll have good take offs and great acceleration... I'm also assuming all the '77 are 4.375 even longbeds? Quote Link to comment
datzenmike Posted September 20, 2009 Report Share Posted September 20, 2009 The '79 isn't sluggish because the '79 tranny compensates for the 4.11 rear end by having a lower ratio 1,2 and 3 gear. Lower than 4.11 would be even more sluggish for acceleration. All 620s had 4.375 ratio rear ends except the '74 automatic and the '79 standard. Quote Link to comment
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