I read somewhere that hinted at having flipped a 3rd gear gear set for a higher fifth gear.

Is there a tech article for this? I havne't seem to have come across it yet in my search.

Or, how is it done?

Have you been inside a tranny before?

If so, get a third gear combo, flip the posistions of how it sits in the third gear posistion and put it in the fith gear posistion.

This will be a real tall fith gear, you may have cooling probs. because of the low rpm's at FRWY speeds.

Keith

That's all there is to it? no machining necessary? The shafts that the gears go on are the same diameter?

Yep!

I'm running a flipped 5th to make a lower 3rd (Ka)... All sorts of options by flipping gears!

Tech article can be found from the '914 Info' link at the top of the window, then 'Technical Articles', then 'Re-gear your 914'. Once in the article look for 914 901 Gear Ratio Workbook it looks like a paragraph header but it is a link to an excel spreadsheet (gint is fixing this.. thanks gint!) Once in the spreadsheet, go to the last tab '901 3rd _ 4th_5th _FLIP_ Chart'

Check out the article too, it will help you with how to use the spreadsheet

I've got the spreadsheet, that's what caused me to start looking for the article. Excellent spreadsheet you've got put together there, I like! it's absolutelty great.

You can swap 3rd gear for 5th gear and you get a lower 3rd gear and a lower 5th gear ratio. There are a couple of issues with this.

The ratios are a bit goofy if you only swap 3rd & 5th around, 4th gear ends up too far from 3rd and to close to fifth.

The angle cut of the gears. Also the angle cut on the gears is wrong for their new rotation, so the thrust under load is not against the thrust washer for each of these gears. In theory you will get increased bearing/gear wear,

I did mine many years ago & I had no problems with it. When I did mine I bought a used 'S' 4th gear and it gave me a nicely spaced shorter 3rd, 4th, 5th combination.

Jim

ummm
I dont get the flip gear tab....
I may just be stupid.

How would I figure out the rpm if I flip 3rd to 5th?
Is there a place to enter that flipped setup?

Also, there is a link on the spreadsheet for tire diameters that Sir Andy built...but that picture is missing or the link is broken...just and fyi.

Rich

Tell me if I am reading this right.

KA (stock third gear) is 22:31
ZD (Stock fifth gear) is 31:22

So you would gain nothing by flipping these...correct?

Rich

on the tabs. There is a scroll bar at the bottom right so you can go further to the right to get more tabs.

Unless of course you mean "understand"; from the looks of the post I quoted, I think you 'get' it now. The flip tab shows which gears correspond to each other. So if you want a close ratio gear box, you can flip different gears that you might have in a particular box from a parts car.

A stock third gear set is a N/23:29 if it's flipped it will give a .793 final. This is not taller.

The best combo is a FLipped HA gearset. this gives about a .6 ish final.

This, I think can be found in a VW 4 Speed gearbox and has a removeable second gear set.

Q: flip gear tab?
A: the dots show what happens when you 'flip' the ratio and gear postions. For example going down the verticle list (3rd/4th gears) the first dot is in the "Ka" row. If you follow that dot down you see that, that ratio is a stock 5th gear "ZD". So the dot indicates that 31:22 ratio is a ZD fifth, and if it's 'flipped' for 3rd or 4th, it is a 22:31 ratio, or "Ka" gear. The dots mark the valid intersections of 3rd/4th gears (vertical column) and 5th gears (horizontal row)
(you can also just compare the ratios and look for a inverted match between the vertical & horizontal axis, e.g. 31:22 and 22:31, the dot just gets you there faster)

Q: How to figure RPM to flip 3rd to 5th
A: In the excel sheet, go to the tab "901 Gear Ratio Model" enter your tire diameter and your RPM redlines. Then below, the first graph shows RPMs/MPH for the stock gearset, then below that you can use the pulldowns to select your 'what if' gear set. The stock 3rd is a N. So from the gear flip table, on the "N" row go over to the 'dot' and follow it down. table says a flipped N is a "Z" fifth. Back on the "901 Gear Ratio Model" use the pull down for 5th gear to select "Z" and that will show RPMs/MPH on the graph.

A couple good setups that I use are Ka-Q-V (Ka is a flipped 5th) and M-S-X

These both work out as nice close ratio setups. Not really good for highway use though! Great track setups.

And thanks for the comment on the missing link to Andy's tire diameter tool! Will get that fixed.

While chatting about gears, I have a few for sale

K,Q,V,Z,ZD I think I have Y also have to check
F Mainshaft (2)

if interesested lemme know.

I'm interested.

I have gears and shafts for sale too. V, ZD, N, O, M, S, X, std (F) shafts, plus every other part you could want.

Also, I second that dropping 5th too far leads to poor cooling.

ooh, thanks. the interest is growing. I need to get some of your CV bolts, too.

Okay one question from me the subie guy. I like my subaru, but yes the 5th isnt tall enough for cruising freeway. My RPM is about 3600 and i am sure my 180hp subie would love to be at 2200 at 75mph instead. So....as i am understanding. I can take a spare transmission that i have...take the 3rd gear out, put in in place of my 5th gear only this time flipped and that will knock my rpm down for 75mph freeway driving?

Thanks in advance

If you have a stock 3rd ("N" gear) flipping it for 5th will actually raise RPMs for 75mph. Follow the steps in the post #5 above to get to the tech article and spreadsheet, and in the spreadsheet look at the "901 Gear Ratios & RPM-MPH Table". That will help you select the needed gear for your RPM/MPH target you have in mind. Once you pick a new 5th, go back to the 901 Gear Ratio Model tab and enter your new 'what if' ratio(s) to see your shift points, etc.

Hope that helps.

Just some eye candy for this thread, here's our 901 with an A-F-M-S-X setup getting it's new DW DesignWerks (BigD914gt here on 914World) billet intermediate plate!

Click to view attachment

Click to view attachment

oooh, nice!
What sort of hp/tq can that handle?

And what is the difference between the 901 shaft and 904 shaft? (the spreadsheet and article mention 904 shafts)

I have no attention span...
Can someone please tell me what the tallest set of gears can be in a tranny?
Meaning, pick from stock gears, flipped or whatever.
What is the tallest possible 5th gear, and what is the difference in RPM for 75mph...please please.

As far as cooling goes on the highway, I will be happy to prove/disprove the urban myth regarding cooling.
when I cruise at 55 trying to keep under 3k or close to it...the cooling is better.
So, if I can get that same rpm range at 65-75, that is my goal.
Cooling I will monitor with dual head temp gauges and oil temp gauges for those who care to see what happens.
I do not believe that it will make alot of cooling issues if I keep the gear within range RPM wise...

I am running 205/50's so that will help raise the RPM,s....but once I get the largest possible gear in there, and I am safely satisfied with the cooling numbers, I have taller tires (winter tires) I can test to see what the results are...RPM/cooling/speed/MPG ....

I want a highway cruising gear that allows the motor to perform in its happy spot...2500-3200...that seems to be the happy zone.

Rich

That intermediate plate is really nice isn't it!

We are running an 86 3.2 in our 914-6. Pretty much stock, so the 901 does ok with it. The 901 will handle more. Not sure the upper limits but maybe others can jump in with those figures.

The stock 901 mainshaft has an integral "F" 2nd gear and it can't be changed out. The 904 shaft allows you to swap out 2nd gear ratios like the other gear positions.

We have the stock "F" mainshaft. Wish I had a 904 mainshaft and some gears, H & I for instance, but that's BIG $$

Cool option is Chris Foley can machine off the "F" on a stock mainshaft and weld in a different 2nd... www.tangerineracing.com

The reason you'd want to change 2nd is to fine tune for a particular application. I'd like to get a perfect gear for turn 11 at Laguna Seca coming onto the straight. The Ka in my 4 is a little to high and the stock F is too low. I found a GA mainshaft out of a 911 I'm going to try next time we rebuild...

here's a chart for (edit: OOPS. not sure what it is for... redoing) the extra line at the bottom shows for the 'H' gear flipped.
straight from Greg's chart in the spreadsheet. (with an added line. Thanks, Greg!)

Here's the MPH chart with the other gears flipped; as noted.

(edit; redoing!).

I am running M S ZD for my 3rd 4th and fifth gears and it seems to work very well. I thought the $th and 5th would be weird but it seems to do well. I only use fifth for the highway anyways. M flows well with the stock 1st and second for AX. Maybe not ideal for a stock four but works for the six.

I studied out the spreadsheet a little bit more so I could understand exactly what you are talking about on the GA shaft...

That looks like a good choice for the somewhere in between, I can see why you'd want to give it a shot.

One quick picture for your short attention span.

I followed your stated goals, and came up with this chart. (first try, still playing)

45mph is going to be a little higher... (2400 RPM in 4th or 3700 in 3rd) I'll play more
55mph 2963 RPM in 4th
65mph 2650(ish) RPMs in 5th
75mph 3041 RPMs in 5th

What you show is an H gear...that is not in the stock box, is it?

Rich

Hi Rich,

Only the A & F gears in the chart above are stock gears for a 914. The M, X and I, all have to be tracked down.

Greg

Just in case you haven't come across it, another part of the tech article on re-gearing is the 'member gear-set library'. You can see what other members are using along with their comments. It may help you with your re-gearing project.

http://www.914world.com/bbs2/index.php?showtopic=79893

Also, when you complete your project, let me know and we'll post your setup!

The HB or I gear flip, seems te be the best combo..

Anything much under 2700RPM's @ frwy speeds will cause cooling issues.

Example: This past Fri. outside temps. where about 95*. I was driving on a backroad with some hills.

while climbing one of the hills, I noticed the head temps in the 370* range @ about 2600rpm with a 13.4 AFR.

I down shifted one gear, rpm's climbed to about 3100 AFR was about 13.2 but the head temps dropped about 8-10*.

When I noticed this I tried it a few more times and YES it was legit.

Things will be different on flat ground and you will probably be fine with a bit of a taller gear but it seems these engines do not like anything under the 2700rpm range( for most engines is the peak of the torque curve) for very long.

Keith

Keith,

Here is the chart with the HB-flip. The only thing I changed from the I-Flip to this chart is the Iflip to HBflip, tire sizes and shift points all stayed the same.

Just an added point of validation.

-Jim

a couple more...

since I'm playing and getting this chart really figured out.

I'm liking the looks of the mods inspired by Keiths suggestions.

just dug this thread up. in my v8 car, i am doing about 70mph at 3000rpm. so a flipped H is, without a doubt, a big upgrade, resulting in about 500 less rpm at 70 mph. the question then is what gears would be better than N (3rd) and V (4th).

looks like this would be best for even gear spacing based on 2500 rpm

F = 21 mph (2nd gear used as 1st)

Q = 37.9 mph (3rd gear) (+17mph +-)

ZA = 56.2 mph (4th gear) (+17mph +-)

flipped H 2500 rpm = 71.8 mph (5th gear) (+17mph +-)

In my V8 I am using an H for 5th. 4th and 3rd are flipped Been a few years ago dont recall the details. First gear removed and locked out. Gear spacing feels very good The H set made a huge crusing differance

For my /6 I'll be using A, F, O, X, HB (flipped)
Dr.Evil helped me with this combo and I built it at his clinic held at my place.

I have never had a complaint with F, O, X, fH. You can use that as your base and adjust, but no one has ever been unhappy or asked for a different gearing. I have only had positive feedback from this combo with more powerful engines.

because I live in the flat land here in SC, and spend a lot of time between 45-50, or then on interstate at 75 mph, when I rebuilt my box at Dr. Evil clinic at Scotty B's a few years ago, I went on his recommendation of doing the HA flipped for 4, and x for 5th.
stock 1,2,3.
now that I have driven in the mountains the past 2 years during Octeenerfest, I notice up there it is a bit of a jump from 3-4 , . but I can tell you I get great gas mil age on the highway, having averages almost 35 mph for stock 2.o d-jet on this past trip to okteenerfest. One other factor. this was a better when I had 15" wheel swith lower profile tires and therefore faster RPMs at lower speed. now with my 205/55/16" fuchs, I would prefer either a bit higher 3 maybe a step or 2 up, say O or P so that there would not be so much of a gap between 3 and 4, or just a stock box, atleast for the mountain driving. . so just a few thoughts - lots of factors, depends on your driving , terrain and speeds, tire/rim combos etc.

Phil

G or GA would be 2nd gear. You also would have gone X for 4 and flipped HA for 5. In a small engine you sacrifice power band for fuel economy. 5th becomes overdrive in your scenario. So, your box should be A, F, N, X, fHA.

Typically, O is substituted for N so bring the top gears closer for street/freeway driving. For a short course A, F, M, S, X are the factory gears to use. Most folks like me to convert their MSX box to taller gears unless they strictly AX it.

Doc, thanks for the correction. I had that reversed on the ha/x .
I spend most of my driving around here in 4th. I don't really get into 5th unless I'm on the interstate, because the revs are so low, also then there is the issue of air movement and running a bit hotter then as a result. I'm going to put an external aux. oil cooler on anyway.

I can say I have no leaks and my shifting is perfect since doing this rebuild 3 years ago.

I am so absolutely confused by this. I am about to rebuild my box and wanted to do it in such a way that If I converted to a six (3.2) that I would be ready for the change. I do not do AX and likely never would. I agree that fourth and fifth (V ZD) are really overdrive gears and not well suited. Saying that I think an AA first would be better than the current A. I don't want to be at 4000 rpm or higher in 5th @ 70mph. Does anyone have a suggestion for me? Looking at the ratio chart I am thinking A - F - flipped ZD - Q - Z/ZA.

I should have mentioned that I am running 205/50/16's.

Based on what you listed, I have no idea what you are attempting to do with your car. Those ratios would suck for most things, except maybe a monster truck.

I'm using CA, H, KA, Q and ZD. I don't have many miles on the car yet, but everything seems to work well and are spaced nicely except the ZD. It feels like a large jump from the Q. I've only driven a few miles on the highway and the ZD really drops the RPMs. The engine is a built 3.0

I'm attempting to bring 3-5th into a tighter ratio and eliminate the very tall ZD set. Monster truck? Please explain.

I have stock 914 gearing (911-901) in my '67 beetle with a 180hp type 4, rear tires are 195/65-15. I'd say the factory got it right for the type four on the street.

I'm getting the parts together for a new motor. The X,HA gear set would be a good combo for the torque curve I'm looking to get.

What are your RPM's are 70mph? (somewhere in the back of my mind I think I asked that Q before, sorry if I have)

I don't temember exactly but it's under 3000 in 5th at 70 . Pretty close to 3000 at 75. I will drive the car to work tomorrow and tell you. Around here on the highway at 55-60 I'm in 4th, and at about 65 will shift to 5th.

I have a 3.2 and have a stock 901 gear for 1-3, X for my 4th, and a flipped H for my 5th. The 4th feels a bit high once coming out of 3rd but it is a cruising gear. The flipped H is a true overdrive. I seem to recall going at least 85mph at about 3000.

I'm looking at possibly a flipped I gear.

I had 205/65/16's on the car for a while. This gave about 4% overdrive. The 1.7 had no problem with it. It really liked it actually. At 70MPh I was spinning approx. 2750-2800rpm and no cooing issues.

The tires were just too tall. I have 205/60/16's on there right now. that's about 1% OD which brought my rpms back to 2900-3000 at 70.

The I gear flip is not much taller than stock and might be a good combo.

I'm kinda scrapping the idea of an X 4th. I think I'll just change 5th and leave the rest of the gear box alone.