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82 720 trans?


wlf89

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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

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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

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