5-speed ratios for stock L series engines.

[LenRobertson]

I've read various forum posts saying some long tail 5-speeds are better suited for a stock or mildly built L series engine. This page: http://newprotest.org/projects/510/gearRatios.pl shows the later 280ZX with a 3.062 First gear. I recall hearing this is too tall a gear, unless you have a 4 cylinder with quite a bit a power, but I may have misunderstood. Does anyone have any experience/opinions on ratios of the various 5-speeds? It is all a bit of a mystery to me. I suppose the answer may be different for cars and trucks, too.

 

Len

[Bleach]

Yes, the 1981-83 non turbo 280ZX has the higher 1st gear, but it also has the higher 5th gear. Keep the rearend gearing the same and I think you'll be just fine. It would probably be better for an L20b though than the L16.

[LenRobertson]

It occurs to me that ratios may be somewhat of a non-issue. It may be a case of getting used to what ever box you happen to find first (and cheap). Also, what type of driving you do - daily driver with lots of traffic lights, freeway driving, or combo. I know the dogleg in my 200SX has a kind of a wide space between a couple of the gears and always seems to loose revs making that shift, more than the other gears. But I don't drive in traffic, so it doesn't bother me too much. Sometime within the next few months, I plan to get my 510 running again with the truck tranny, so I can compare it with the SX & dogleg.

[datsunaholic]

I have various setups. My '78 4X4 has a truck 5-speed from a 77-78 truck, which is the same ratios as the '77-78 280Z 5-speed. I find that setup to be the best all-around for the vehicle since it directly replaced the 4-speed in 1-4, but added that overdrive for the freeway and made it possible to make old Ryan quite uncomfortable following me up I-5 (how fast WAS I going, Bleach? Was a few years ago).

 

My '74 620, until the engine blew up, had a Dogleg on an L20B. It also was OK for a truck being used as a truck, BUT the transmission is notoriously weak. I don't even attempt burnouts so it wasn't abused. Same tranny in my '78 510 was likewise suited for what I was doing, and I'll put a dogleg in my '78 wagon when I change engines (the old one just leaks too much and at 310,000 miles it's time).

 

My '76 KC has the weird setup. It has an L18 with an L20B head and manifold set (which makes it have very little low-end torque), and a high-lean setup Weber 32/36 (jetted for a 1.4L B210). The clincher is that's the truck I stuck the big-overdrive '82 280ZX tranny in. Your really gotta wind it up and slip the clutch to get it moving up a hill with any sort of load in the back, 1st gear is just not low enough. But, the mileage (32-35) is pretty dang good, and it'll go fast enough to make the steering get squirrelly (somewhat reduced by my having lowered only the front, downforce and all)

 

I built this little chart a few years ago that gives a general idea of what to expect in 5th with different transmission/rear end combos, but it also lists the ratios as published in the FACTORY manuals that I have. Sometimes they vary too, as things changed during the model years. This is for trucks, I didn't write one for cars, but the idea is similar:

 

http://64.125.210.117/datsun/gearratios.txt

[NWOleman]

Hey Len hows it going? It's not just the tranny ratio you have to figure on, it's the rearend gear ratio and tire height too. It is complicated tho. Then you got to figure the weight of the vehicle is gonna matter and then how much power your motor is making. For example in a 510 sedan compared to a heavier pickup you could have the same motor tranny rearend and im pretty sure the 510 would run circles around the pickup. The old saying "gears are the cheapest horsepower you can get" is a reference to this. Now put in lower rearend gears in the pickup and it will run with the 510. Do ya see what im saying? Of course out on the hwy it all changes. Anyways im rambling, sorry.

[LenRobertson]

Thanks everyone for the input. The truck trans I got seems to have the 3.321 First gear and the ratios for that trans don't seem much different from a dogleg, which is what I'm used to in my 200SX. I don't expect to change rear end ratios. I believe the common Subaru LSD ratio is close to a 510, so even if I found one, I wouldn't be changing ratios much. I almost never see a Subaru at P&S that hasn't had the tag wiped clean. Someone else is looking, too.

 

Tire size is a big unknown at the moment. I've been running both 13" and 14" steel wheels. I suspect I'll end up with 14" Z wheels, since I can probably find some at P&S or local tire store for cheap.

 

When I think about it, the whole ratio question is probably something I shouldn't be concerned about. It seems like every couple of weeks I'll be half way to work and realize I've forgotten to shift from 4th gear to 5th. Mornings the coffee is slow to kick in.

 

Len

[banzai510(hainz)]

remember the later 200sx 80-83 or what ever those years are had the 1st gear up. You can still use those transmissions.

you can swap the 77-79 bellhousing on to them to get rid of the 15deg angle.

 

Jeff Hino has done it with a KA /280 Z trans if need more info.

 

so those 80-83 and maybe later truck trans(KA)trans are still good if found.

[LenRobertson]

Is there anything tricky about the bell housing swap to the newer trans? The shims on bearings aren't disturbed or anything? Does a gasket have to be replaced? If my truck 5-speed turns out to be junk, it can be a bell housing donor, if the swap is easy.

 

Len

[banzai510(hainz)]

PM Jeff Hino (ice house)

 

he just reglued his back together

he has photos of this also

 

but break it from the front (spacer)