Hi,
What is the highest or tallest 5th gear combination that can be created using stock gears from a spare tranny...i.e. remove some gear set from one tranny, and put it into the other tranny to make a tranny that has a really tall 5th gear...

I am trying to get the best highway MPG without buying a special gear.

Rich

it has to be a flipped third gear (in a 5 speed or second in a 4 speed)

im pretty sure flipped H is the tallest you can go...with off the shelf gears

Just put bigger tires on it.
But I would be cautious of that because the engine my turn too slow and might over heat.
What 30MPG ain't good enough?
get a early 1.7L I was getting 32 MPG at 80 MPH.

Flipped third gear...
that means take the third gear (both drive and driven) gear set off of one tranny...
Flip them over,
Put them on the new setup but put the third gear drive on the fifth gear driven and put the third gear driven on the fifth gear drive...

And what does that do in comparison the to the stock gear??

I.E (Oh master of the gear chart) at a given speed,,,,say 75 MPH...what is the difference in RPM's with that setup between stock and the third gear flipped???

Thanx..
Rich

an H gear is a second gear in a 902 4 speed (out of an early 912)
so you take the H, flip it over, change the shaft placement and put it in 5th gear spot.....

lemme run some numbers.... im pretty sure a flipped H is the tallest you can go...

as a flipped stock third is still waaaay short.

NOT an H gear...
I want the tallest I can do with the stock gears available..
I know I can buy something taller (an H gear for instance)
I want to do this with stock parts....

Rich

with an H gear in 5th.... and 25" tires...

80 mph is between 2500-3000RPM about 2600...
80 mph w/ stock ZD is just under 3500 RPM

you're hosed then. ZD is the TALLEST 5th gear made......

H is a stock gear in a 902 box... go find one

You really don't want to run a stock Type 4 at slower than 3000rpm at highway speeds. The fan has to keep turning at a certain minimum speed to prevent overheating. Indeed, there's evidence to show you want to keep it in 4th as high as 75mph, to keep the revs up above 3500rpm, or your heads will get too hot. 5th is really only useful for cruising at German-class speeds.

Is ZD stock in a normal 5 speed gear box???

I guess I will go back to original question...
what is the tallest 5th gear I can put in using STOCK gears from another 5 speed 914 gear box...
If the answer is the stock 5th gear...ok..that is the answer...
If going to the flipped 3rd gear is a little bit taller...ok that is the answer...

I am confused now..

Rich

with a tall 5th you'll be way below the power band when driving at normal freeway speeds. more time in 4th negating the mileage increase.

k

yes. ZD is the tallest stock 5th gear available, and it happens to be the 5th gear in 914 gear boxes (/6's had a slightly shorter one)

H gear, is a second gear. flip the ratio blah blah and you get THE TALLEST AVAILABLE RATIO

No other third gear flip will get you taller than a ZD.


thus you are hosed

Not really, seeing as I dont have the stock 5th gear now....by going to the stock 5th gear...I will get an increase in mpg...I am asking cause I dont want to do this, then find out I could have grabbed a different set at could have gotten better MPG in the long run...

Speaking of the early 4-speed boxes (901 based?) - what parts/gears, etc. are interchangable with the 914 trans?
And where exactly is 1st on the 4-speed trans? Is it in 2nd location on the 914? I guess what I'm trying to ask is - can you transplant the gearing from a 4 speed trans into a 914 trans and possibly eliminate the weak 1st gear (for higher HP applications - of course!). Would such a swap require the matching R&P from the 4-speed?

Jeff

took me some time to find
now 27:25 is my ratio..on 5th

which puts me at 4500 at 75 mph...
So stock will drop me to 3500 at 75mph...is that correct...at least that is what I am reading...

Rich

Aaron,

If you put a flipped H on 5th, wouldn't you need to move 4th up a bit
as well? You said the rpms @ 80 would drop from around 3500 to 2600.
That sounds to me like a whole 'nuther gear could fit in between 4th
and 5th.

Skip

True for sixes as well?

Skip

ideally yes... but he is asking for the tallest available gear set......

Yes, you can. You'll end up with a 4 speed (of course). I have an A mainshaft (1st gear ratio in what would be the second gear spot) for sale, if you're interested. You don't need to switch the ring and pinion, just the mainshaft and whatever gears you plan to use. You'll need a suitable second gear though, H or HB probably.

Not much else is compatible between the 902 and 914 trans.. int. plate is different, bearings are smaller, case can't handle a flipped ring gear.

The standard thing to do is move the old 5th to 4th, move 4th to third (and flip) and remove third. That spaces them pretty evenly. Good for V8s, bad for type IVs.

quick question, with somewhat a level of revelence.

Is it "bad" to cruise a 1.7 at 3800-3900 rpms in 5th for freeway speed?
Seems this is where my car likes to chill...

Didn't Joe Yoder put in a taller 5th gear in his -4 when Milo and him did their roundy round. HB gearset maybe? Sporto gear?

And so-so for sixes?

S

the factoy put a shorter 5th gear in the six tranny.... maybe to keep the fan speed up...