Will a 5 speed pay for itself?

[EverRude]

My 71 still has original 2.4 4 speed. I have a Zcar friend that has a good 5 speed from a 78 280z he's doing a motor swap on. He'll sell it to me for 250. Will the fuel economy difference pay for itself on a daily driver z in say, 6 months?

Or are there better places to spend money for economy. I'll have new carbs and all new stock ignition setup... plugs wires points etc...already.

Edited April 4, 2011 by EverRude

[Arne]

There will be no fuel economy difference at anything other than highway speeds. At those speeds, you might pick up a couple MPG, maybe. Saving $250 will require you to save somewhere between 60-70 gallons to pay back. That's going to be hard to do in a short period. I'd say the payback period for most of us would be more like several years, easily.

When you also consider that installing it in a '71 will require either a modified shift lever (cut and welded), or tunnel and console mods, I can't see that it is worth it if economy is your only goal.

[GTTED]

Might help a little in economy, but it will definitely help in the driving experience overall. Make sure your car is tuned correctly and tires inflated and enjoy the ride.

[ZCurves]

Buy and re-sell, you might just double your $$$.

[EverRude]

I drive 200 miles a week highway averaging 70 mph. 70 miles or so a week city averaging maybe 25 mph.

What other goal would having a 5 speed meet? They stronger? Or better ratios for shifting.

Actually my car doesn't have original console and its tunnel has been cut with a torch on the front right area of the opening. Right where 5th gear would be. Actually wondering whether it had a 5 speed at some point.

[ezzzzzzz]

Not the way I DRIVE! HA! 5th gear will allow you to use a higher R&P for more spirited driving in 1 through 3 and still maintain comparable economy of a 4 speed. I run a 3.90 R&P and usually don't use 5th until I'm cruising around 60+. My trans is a KA with the L28 bellhousing conversion.

[Arne]

I drive 200 miles a week highway averaging 70 mph. 70 miles or so a week city averaging maybe 25 mph.

Payback will be slow, with that use.

What other goal would having a 5 speed meet? They stronger? Or better ratios for shifting.

Stronger than the original '70-71 4 speed, perhaps. Not than a later 4 speed. (See next comment.) Quieter, more relaxed cruising on the freeway with the 5 speed. Or you could change the read diff for a lower ratio and get some performance increase while still maintaining top gear ratio of the four speed.

Actually my car doesn't have original console and its tunnel has been cut with a torch on the front right area of the opening. Right where 5th gear would be. Actually wondering whether it had a 5 speed at some point.

Maybe, but it is also possible that it has had a later 4 sped put in it, which requires the same mods. Is your shift lever a totally straight rod? Or is is 'S' shaped? Edited April 4, 2011 by Arne

[mayitin]

I do not look at the way you do. A 5 speed is always going to be better specially if you drive on the highway, revs will be low and you will hear better your stereo hahaha . it will help eventually with the economy. You will need also a well tune motor, play with your timimg make sure your valves are adjusted right inflate your tires like GTTE advised use a 10w 30 oil or just 30W. I am old school i never did anything to my car that was going to give me less MPG or less power, if it would give me more power without affecting my mileage I would do it. Play with your spark plug gap get a hotter coil, change to electronic ignition. Maybe you should ask what have we done to our cars to get better mileage.

[EverRude]

I do not look at the way you do. A 5 speed is always going to be better specially if you drive on the highway, revs will be low and you will hear better your stereo hahaha . it will help eventually with the economy. You will need also a well tune motor, play with your timimg make sure your valves are adjusted right inflate your tires like GTTE advised use a 10w 30 oil or just 30W. I am old school i never did anything to my car that was going to give me less MPG or less power, if it would give me more power without affecting my mileage I would do it. Play with your spark plug gap get a hotter coil, change to electronic ignition. Maybe you should ask what have we done to our cars to get better mileage.

It isn't just about mileage though. This is more of a "can I sell it" situation for Mrs Moneypenny... I could out and out lie. But haven't done that in 20 years about something I wanted. She's my partener and financial manager. I want her input but she needs facts to help me decide.

So at 200 hwy miles a week. With current gas prices. It would take a year for the tranny to pay for itself on a purely economics footing. The other benefits also factor in. Quieter. Less wear on engine. Etc... Also I add the fact I would then have a spare transmission in the event of a failure of the 5 speed.

Maybe, but it is also possible that it has had a later 4 sped put in it, which requires the same mods. Is your shift lever a totally straight rod? Or is is 'S' shaped?

S shaped. Posting pics Below. Think you may be right. Type B 4 speed?

[Arne]

S shaped. Posting pics Below. Think you may be right. Type B 4 speed?

Yup, looks like a Type B, from '72-78. No further mods needed for the 5 speed. Or at worst, perhaps the need to trim the already-trimmed spots a bit more for the extra cog.

[jmortensen]

Your 71 has a 3.36 rear end from the factory. Adding the 280Z five speed will gain you a little mpg, but the gearing is a bit tall (280Z's came with 3.54's). I'd sooner follow ezzzzzz's prescription and get the ZX five speed and a 3.90 or 4.11 diff. That would make for a much more lively car.

[kenz240z]

You might want to check the salvage yards. I got a whole '82 ZX for $300 from a local salvage yard. The L28 and 5-speed are in my orange '73. The 3.9 R200 is in my V8 project Z.