datzenmike Posted September 25, 2011 Report Share Posted September 25, 2011 Good point but the factory gearing also takes into account a fully loaded truck needs to be able to get up to highway speed and climb hill and such. If you are strictly using for commuting all the revving on the highway can be reduced. The '79 620 4 and 5 speed came with a 4.11 rear diff from the factory, down from the 4.375 of earlier years. To compensate for the lower ratio on take offs with a heavy load, a much lower 1st gear ratio or wide ratio transmission was used. Going to a 4.11 or even a 3.889 is doable on an empty truck. Acceleration would be less than the stock gearing for sure. Quote Link to comment
wildmaninid Posted September 25, 2011 Author Report Share Posted September 25, 2011 Both are valid arguements. If I was using my truck like a truck, hauling loads, sticking close to home etc, even with the increased horsepower, I would have been inclined to just leave the gearing alone. For me it made sense twofold: I only haul light loads, and if I do haul something heavy its never more than a few miles, and I want to do lots of sustained hiway speeds. So putting in taller gears made perfect sense. These are things you will need to weigh when making your decision. As far as doing the swap, it took me an hour and a half to remove the carrier from both my truck and my donor, swap them over and put each back together. My donor truck needed to be moveable so I had to do that. Just need to support the vehicle, remove driveline and wheels, drain fluid, remove the 4 bolts on each side of the axle tube which will allow you to slide the axle, backing plate and all, outward, disengaging the axle from the carrier. Remove all the nuts around the carrier and drop it out. Clean everything up, seal the carrier to the housing and reverse wrenches. Pretty easy all in all. Quote Link to comment
jrock4224 Posted December 16, 2011 Report Share Posted December 16, 2011 oh shit datzen mike served it up again... plus what are we talking between all the truck with h 190 like a 15 horse power swing... whats a good ratio for a non working (no heavy lifting) 521 i was thinking 3.89 but this has me thiunking taller now... that 2300 at 60mph is sexy as hell...i could answer my phone then...if it were legal...i have a l20 and a 5sp on its way in but l16 4sp for now ...swap is in the nerxt two monthes but in the mean timei dont mind down shifiting or lkuggin my l16 till its a 5 sp l20 Quote Link to comment
wildmaninid Posted December 16, 2011 Author Report Share Posted December 16, 2011 oh shit datzen mike served it up again... plus what are we talking between all the truck with h 190 like a 15 horse power swing... whats a good ratio for a non working (no heavy lifting) 521 i was thinking 3.89 but this has me thiunking taller now... that 2300 at 60mph is sexy as hell...i could answer my phone then...if it were legal...i have a l20 and a 5sp on its way in but l16 4sp for now ...swap is in the nerxt two monthes but in the mean timei dont mind down shifiting or lkuggin my l16 till its a 5 sp l20 I would stick with the 3.89. For all intents and purposes, that ratio is ideal for upgrading from the factory 521 ratio. I am still rocking the 3.50 ratio in the 620. There is no way that I would have went that tall without doing the KA swap. With the power the l20 makes, I think that is as tall as I would want to go, and should give you a nice 60 mph rpm. Quote Link to comment
Laecaon Posted December 16, 2011 Report Share Posted December 16, 2011 My friend has a 521 with 3.89 in it, it likes to do burnouts in first gear with the wimpy L16. It does everything fine. Quote Link to comment
jrock4224 Posted December 17, 2011 Report Share Posted December 17, 2011 oh shit datzen mike served it up again... plus what are we talking between all the truck with h 190 like a 15 horse power swing... whats a good ratio for a non working (no heavy lifting) 521 i was thinking 3.89 but this has me thiunking taller now... that 2300 at 60mph is sexy as hell...i could answer my phone then...if it were legal...i have a l20 and a 5sp on its way in but l16 4sp for now ...swap is in the nerxt two monthes but in the mean timei dont mind down shifiting or lkuggin my l16 till its a 5 sp l20 this is why u shouldnt text or forum and drive.... i will issue a decoder ring for my hot dog hands form of typing ... Quote Link to comment
jrock4224 Posted December 17, 2011 Report Share Posted December 17, 2011 thanks wild how did everything turn out after your shop fire... i have a ka24 and auto tranny i got for a song but iam saving for a 4 dr or wagon project....this truck will be bagged and i think i will stop at l20 and 5 sp for performance... its my around town truck... just rught now i hate the freeway with my 17's i feel like everyones going 80mph and i am about to bend a valve trying to do the speed limit....3.89 it is . then supposed to be nice this weekend might be the weekend to go lay in a junk yard and stare at the bottom of truck beds Quote Link to comment
wildmaninid Posted December 17, 2011 Author Report Share Posted December 17, 2011 Its good, it was at the ex wifes place anyhow, so no worries to me....lost a few things, but that seems like forever ago now. I have the ka in the 620, all pretty, 4 wheel disc and a new interior. Waiting for springtime so I can get her back out again and banging out some more bodywork to prepare for canby. Quote Link to comment
jrock4224 Posted December 17, 2011 Report Share Posted December 17, 2011 gonna try to make it to canby this year with my buddys 510, south paw, assuming i can finish the rest of the paint work this weekend and we can start assembling and probably my 521 by then too... glad to hear your back up and running... i thought u were a 521 guy now u got a 620, huh i will have to search the build threads and check it out sounds cool running a ka Quote Link to comment
jrock4224 Posted December 17, 2011 Report Share Posted December 17, 2011 man i spent a week in coure de laine in a cabin on the water, back in sept, i shoulda hoollered at u made u come over and go swimming .....my boat was blown up so it was rest and relaxation...which worked out good cause everyone always wants to go for a wide open pass... Quote Link to comment
wayno Posted December 17, 2011 Report Share Posted December 17, 2011 I swapped a 350 gearset into my kingcab 521 with a SD25 diesel engine, the truck hauls ass on the freeway, 3000rpm is about 80mph, it was great. As it is a diesel, starting out wasn't that big of an issue, it was a little slower, but now I don't notice it anymore. I even loaded it a little on my trip to LA, it wasn't any differant with 500lbs in the back, other than it bottoming out the whole trip, need to notch the rear axle frame soon. Your 620 with a KA should kick ass, as it is lighter. Quote Link to comment
wildmaninid Posted December 17, 2011 Author Report Share Posted December 17, 2011 Well, let's put it this way, my brother and I took the 620 out for some top speed runs over at his place in montana in september, and around 124 I started to have a modicum of fear, especially since I still had plenty of pedal left......definitely hauls just a little bit of ass! Quote Link to comment
jrock4224 Posted December 19, 2011 Report Share Posted December 19, 2011 I swapped a 350 gearset into my kingcab 521 with a SD25 diesel engine, the truck hauls ass on the freeway, 3000rpm is about 80mph, it was great. As it is a diesel, starting out wasn't that big of an issue, it was a little slower, but now I don't notice it anymore. I even loaded it a little on my trip to LA, it wasn't any differant with 500lbs in the back, other than it bottoming out the whole trip, need to notch the rear axle frame soon. Your 620 with a KA should kick ass, as it is lighter. so wayno u thinking I would want a 350 ratio for my l 20 swap....I am not looking for a rocket off the line, I am looking for smooth operatiing range...I am not gonna swap my ka in to my 521 ... i will save it .... for my 510 on my x mas wissh list...which probably wont come... Quote Link to comment
jrock4224 Posted December 19, 2011 Report Share Posted December 19, 2011 wild, 124 really.....holy ship......I would be soiling my stuff a 100 in my datsun... Quote Link to comment
yello620 Posted December 19, 2011 Report Share Posted December 19, 2011 so wayno u thinking I would want a 350 ratio for my l 20 swap....I am not looking for a rocket off the line, I am looking for smooth operatiing range...I am not gonna swap my ka in to my 521 ... i will save it .... for my 510 on my x mas wissh list...which probably wont come... 3.50's are way too much for the L20. I found that the 3.70's were about the limit for my L20, and was much happier when i took them out and out 3.89's in. Jrock, remember that wayno is running a diesel in his with those 3.50 gears, that makes a big difference. Quote Link to comment
jrock4224 Posted December 19, 2011 Report Share Posted December 19, 2011 thanks yello.... so is tht a 4sp or 5 sp u are running on your truck with the l 20? and do u know the rpm your pulling with the 3.89 and 3.70 at 70? Quote Link to comment
yello620 Posted December 19, 2011 Report Share Posted December 19, 2011 Jrock, I started with stock 4.37 and a 4 spd and I didnt like the RPM's or the cab noise. So i swapped in a 4.11 gearset, this swap seemed like a waste of time, as it was not enough change with the 4spd still in it. So I went for a big change and installed a 3.70 gearset, still using the 4spd. And these seemed ok at the time, but I found i was into the secondary of the carb just to maintain traffic speed on the highway(65+). These would have been terrible with a 5 spd. So then i decided to try a 3.9 gearset, still 4spd, And these were very acceptable, power from a start excellent, highway rpm's good, not into the secondary of the carb on the highway, happy with them. Then i installed a 5spd, still good in first gear, and the highway was acceptable, yet getting close to the secondary in the carb. But good acceleration on the highway too when needed. But apparently none of that was enough power, cause i got rid of the L motor and installed a VG in my 620. Now the power is acceptable. :D I might actually be going back to a 4.11 gearset in the future due to the overdrive ratio of the VG transmission. But it wont be in a Datsun rearend if that happens. Quote Link to comment
jrock4224 Posted December 20, 2011 Report Share Posted December 20, 2011 hahahahah yeah i would go 411 wit the vg fer sure.....thanks for the detailed response thats exactly the info needed and broke down perfect thanks brother.... Quote Link to comment
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