General Chat
Q:
has anyone been able to come up with a replacement gear for a 280zx 5 speed gear box to bring rpms down on the high way??? with todays modern cars cruising 70 and above in highways need to bring rpms down from 2800rpm...can it be done?? a buddy of mine has asked the same question for years with no answers..and he's a mechanic...
A:
late model 5-speed, and a 3.36 diff.
keep in mind... if you dont have a powerful motor... youll be sloooooooow.
77Z- (mfg. 7/77)
"Arm-chair Autox'er"
A:
Why would you want to do that? It's perfectly fine to run it at those RPMs.
That's about where my Z and 2002 Ford Focus run on the freeway.
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1976 Datsun 280Z 2+2:
-'81 L28ET with 1984 Z31 ECCS
-'81 Turbo snowflakes
-205/60/15 BFG G-Force Sports
-Tokico springs and HP shocks
A:
I'm at 3k at 70 on the freeway, in 5th gear.
77' 5-speed, and a 3.70 diff.... I get like 27 highway mpg.
Search for TonyD's write-up on keeping the car at peak torque and mpg's.
77Z- (mfg. 7/77)
"Arm-chair Autox'er"
A:
Yea, late model 5-speed, and a 3.36 diff. These old cars waste 40hp due to frictional losses alone at 5K rpm. Throw in wind drag and 3-4K rpm it's not great at all.
I run one car with the late 5 speed and 3.36 at around 2300rpm on the highway and easily get 27-28mpg withe the A/C on! As long as the road is level, 2200-2300rpm is great.
A:
"I run one car with the late 5 speed and 3.36 at around 2300rpm on the highway and easily get 27-28mpg withe the A/C on! As long as the road is level, 2200-2300rpm is great."
It's good that you said that Hybrid, something that may not be considered. Around me in the mountains that setup would suck. I've ran it back when I thought I could get more top end - I hadn't been Tony educated!
I would say even the late 5spd with a stock 3.54 works well. You can still launch spinning wheels, and the upper end pull is great.
But these motors like to be in the 2800-3200 rpm range, they are very efficient there. I would think the late 5spd & 3.36 with a turbo motor would have some great pull as well.
Matt
A:
My everyday mileage actually went up 1-2 mpg when I switched to steeper gears inside my tranny by swapping countershafts.
However my Hwy mileage dropped almost 3 mpg when going from the stock .75 overdrive to the .83 overdrive, which would be like going from a 2.92 to a 3.32 rear gear.
Later,Norm
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12.804 @ 107.26 mph on crappy street tires with Dual SU Powered 2.9L Stroker!
ZCAR.COM member since Aug 1998
A:
I get like 29mpg on the highway running around 3000 rpm with an early 5 speed and 3.54 rear end...it runs smooth too...these engines are designed to like the 2800-3200 rpm range like matt said
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1978 280z
5 speed
3-2-1 MSA headers
140,000 original miles
http://www.cardomain.com/memberpage/585326
A:
thats a higher gear, not lower
If all were equal, none would be strong.
Ballistic,Ruler of Interstates
Stage XX+ 1993 Z32 NA
"SoulTaker"