wlf89 Posted April 8, 2014 Report Share Posted April 8, 2014 have a 82 720 with 2.2 and 5 speed trans. do these have overdrive? I don't think so because at 55mph im running about 2800rpm. so my question is are there a 5 speeds trans with overdrive that I could use without much trouble on this truck? Quote Link to comment
Z-train Posted April 8, 2014 Report Share Posted April 8, 2014 You're in fourth gear.A 5 speed Datsun transmission does not exist.Now a 4 speed with OD does. Quote Link to comment
datzenmike Posted April 8, 2014 Report Share Posted April 8, 2014 All 720 5 speeds have an overdrive 5th gear. Fourth is one to one, and fifth is about 12-14% overdrive. 2,800 sounds about right for a truck. Don't forget it is a truck intended to haul loads. There is an engine tag under the pass side hood hinge on the inner fender. If you have a 5 speed it will say FS5W71B. A four speed is F4W71B Quote Link to comment
wlf89 Posted April 8, 2014 Author Report Share Posted April 8, 2014 ok just thought 2800 rpm sounded high for overdrive Quote Link to comment
flatcat19 Posted April 8, 2014 Report Share Posted April 8, 2014 Change your rear gear. Quote Link to comment
ggzilla Posted April 8, 2014 Report Share Posted April 8, 2014 2800 is not high. You gotta remember these engines rev higher than most engines of the early 1980s. The Z22 is happy to cruise at 4000 rpm all day. Or you could swap in a Datsun non-overdrive 5-speed for maximum performance. The overdrive makes it slower, but increases highway fuel economy. Quote Link to comment
jrock4224 Posted April 8, 2014 Report Share Posted April 8, 2014 ok just thought 2800 rpm sounded high for overdrive huh? are u drunk Quote Link to comment
jrock4224 Posted April 8, 2014 Report Share Posted April 8, 2014 i has a napz 5speed in my 521 with 3.88 and it will cruise 75 all day ... well with the l20 the l 16 in it now remains to be seen Quote Link to comment
datzenmike Posted April 9, 2014 Report Share Posted April 9, 2014 I'm making some assumptions here, there were a variety of tire differential choices those years on the 720 With 195/75R14 tires, 2wd, 3.889 differential and in 4th gear at 55MPH is 2818 RPMs. Fifth should be almost 2,400 RPM Quote Link to comment
jrock4224 Posted April 9, 2014 Report Share Posted April 9, 2014 lol mike your assumptions are fact based and truth oriented Quote Link to comment
Robert Posted April 10, 2014 Report Share Posted April 10, 2014 Change your rear gear. Exactly. The tranny doesnt determine the rpm your cruising at. The 5 speeds all have a OD final....its the axle gear ratio. I had three rear end third members. A 3.7 and a 3.9 and a 4.11. at 70mph I am at 3400 rpms with my 4.11 and my 245 50 15s. 29mpg, with the 3.7 195/75 14s it gets 34. This is with a 5W and a KA24DE. Unfourtunately the 4.11 is slower than the 3.70 when it comes to time slips. Quote Link to comment
Z-train Posted April 10, 2014 Report Share Posted April 10, 2014 Just tossing another set of gears in there is really not a good idea.THe gears & box came from the factory like that for a reason.Rule of thumb is for every 10% increase in power,you can decrease the gear ratio the same % with no adverse effects.If you just drop the gear ratio something,somewhere will change for the worse. Quote Link to comment
Omelet720 Posted April 10, 2014 Report Share Posted April 10, 2014 So if I have a stock z24 with 4.375 gears and swap in a 3.5 or 3.7 with smaller diameter tires, I'm going to have issues? Anything else I need to know when swapping gears? Quote Link to comment
Z-train Posted April 10, 2014 Report Share Posted April 10, 2014 If you do the swap,top end will improve,low end will vanish,the truck will be a dog at anything other than freeway speeds and it's ability to carry weight will be gone.ANd if the gear swap is low enough,the resulting cruising rpm could actually make fuel consumption worse. Quote Link to comment
millican Posted April 11, 2014 Report Share Posted April 11, 2014 When I want to go faster than 55, I ride my scooter. However, I do have a transmission from a 720 (diesel) sitting in the back of the truck I intend to open up to peek inside. You or anyone else are welcome to join in on that. Quote Link to comment
Z-train Posted April 11, 2014 Report Share Posted April 11, 2014 I believe Diesel boxes were all 4 speeds.Mike can confirm.If so,then it's worthless to you. Quote Link to comment
datzenmike Posted April 12, 2014 Report Share Posted April 12, 2014 Strangely all SD22 and SD25 diesels came only with 5 speeds. Quote Link to comment
Omelet720 Posted April 12, 2014 Report Share Posted April 12, 2014 Thanks for the reply Z-train. I'm downsizing tires, so to keep my ratios the same I want a higher gear. I was thinking about the axle-end shims. Do you need to add or remove any when changing gear sets? I remember reading about the number of shims in the FSM, but I just want to be certain. Quote Link to comment
ggzilla Posted April 12, 2014 Report Share Posted April 12, 2014 Do not change the shims, which are for bearing end-play. If you change the bearings, that is the time to re-measure and shim accordingly. Quote Link to comment
ggzilla Posted April 12, 2014 Report Share Posted April 12, 2014 I'm downsizing tires, so to keep my ratios the same I want a higher gear.That's right, changing tires with a different diameter tire will affect the overall final drive ratio. But instead of changing the final drive to compensate, try it as-is. With the Z-series engines, Nissan used various ratios. And the Z22 likes to rev. You might even find that your speedometer reads more correct, especially if it now has taller than stock tires. If not, a $16 gear from Nissan will adjust the speedometer. Factory tire size is 195/75R14 for 2WD. Quote Link to comment
Omelet720 Posted April 13, 2014 Report Share Posted April 13, 2014 Thanks ggzilla. I'll do some more reading on adjusting the shims as I would like to replace the bearings. Maybe races? I believe my stock tires were 195/70r14, and I went with a 215/75r14. They rub, amongst other things.... so I'm going to go to 205/50(55)r15x7. I'll try it out with out swapping gears first. I think I'll start a thread in project datto so I'm not jacking this thread :P Quote Link to comment
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