914 901 Gear Ratios, Tech Article, Gear Ratio Workbook, Member Gear Set Library Options

[race914]

To maximize my 914's performance on the track, I've put together several different gear sets for my 901. This has helped me to maximize my top speed on the straights, as well as acceleration out of the corners. This has proved to be a great advantage over stock geared 914s.

I want share the info I’ve collected, as well as what I’ve learned from these projects.

I’ve put together a Gear Ratio Tech Article that includes: why you might consider re-gearing; ways to approach this project; the 914 901 Gear Ratio Workbook (MS Excel required); and references to 914World members that provide related products & services.

Lastly, and perhaps most importantly, I’ll be maintaining the Member Gear Set Library that includes the various gear ratio setups that Members are using for different applications & situations. This centralized repository will greatly facilitate finding information applicable to your re-gearing project. Important Note! The ‘right’ gear set for you is particular to many factors. To list a few, the car’s weight, suspension, engine, and DRIVER! Don’t take the gear-sets listed for a particular application as your ideal setup. Contact the owner, compare corner speeds, suspension setups, engine characteristics, driving skills, etc. All of these factors play into what will work for you.

If you'd like to contribute to the "Member Gear Set library", post your info on this thread and include:

* Applicable Category (Autocross, Street, Track (including track name)
* Engine (cc & cylinders),
* HP,
* Redline RPM,
* Tire Diameter,
* Weight w/driver,
* 1st-5th gear codes, and
* Any short comment that you’d like to pass on, or better yet, a link to the applicable 914World discussion thread on your setup

[neilca]

This is for road racing at Road Atlanta and Roebling Road.
2.0 liter six cylinder
175 hp
max 7500 rpm
tire diameter 23.6
Gears A, I, N, S, X

I have not run the box as yet but these ratios are suppose to work well on track. These are very fast tracks so first igear s considered to be a pit gear only.

[grantsfo]

* Applicable Category Track: Laguna Seca
* Engine 2480cc Six
* HP: 200
* Redline RPM: 7400 RPM
* Tire Diameter: 25.2 and 23
* 1st-5th gear codes and A F M S X
Video of the car on 25.2" tires: http://www.youtube.com/watch?v=aSaL5XpVTt8

On 23" tires the car accelerates even faster and can be shifted into 5th gear on long straights as opposed to 4th.

[911quest]

* Applicable Category Track: Daytona rennsport III
* Engine 2.0 type 4
* HP: not enough (IMG:style_emoticons/default/biggrin.gif)
* Tire Diameter: 21.5
* 1st-5th gear codes and A F M S Z

Worked ok not quite right for Daytona....

914 #59

Tony

[stownsen914]

* Applicable Category Track: Watkins Glen, Lime Rock
* Engine 2.7L 6
* Max RPM 7500
* HP: 260
* Tire Diameter: 25.5"
* 1st-5th gear codes and A KA P S U

A little tall for Lime Rock, good for Watkins. I have also used a GA first gear at Pocono Raceway, which has a hairpin turns in some configurations. 5 usable track gears!

Scott

[HAM Inc]

Scott how did you get a GA first? Also are you using a 904 mainshaft? If I understand correctly you can use any 2nd through 5th gear in any position on a 904 shaft. Correct?
Len

[stownsen914]

Scott how did you get a GA first? Also are you using a 904 mainshaft? If I understand correctly you can use any 2nd through 5th gear in any position on a 904 shaft. Correct?
Len

Len,

The way I did it was to:
1. Take the fixed gear from a stock first gearset, and turn it down on a lathe to knock off the teeth.
2. Sacrifice a GA mainshaft by cutting the shaft off. Then bore a hole in the gear just large enough so it can be pressed onto the turned-down first gear from #1 above.
3. TIG weld the assembly.
4. The standard non-fixed gear from the GA gearset just plops right into place without mods.

Note that you don't get reverse when you do this mod, since there is no matching reverse idler gear.

Ideally I could have annealed the gears before welding and then re-heat treated, but I did not have that done. The gearset held up OK, though I recently had a bearing plate warp and a mainshaft bearing go bad in my trans. Could be due to use of first gear on the track, since that is a weak spot in the 901? The GA first does make for a killer close ratio gearbox though ...

I have heard that another way to accomplish all this is to use a GA second gearset from a 904 mainshaft. You can have an adapter made to match the larger 904 second gear internal splines to the first gear splines.

Scott

[orange914]

(IMG:style_emoticons/default/confused24.gif) where is the transaxle code located?

mike

[race914]

(IMG:style_emoticons/default/confused24.gif) where is the transaxle code located?

mike

Mike,

It should be stamped on the bottom of the case.

Does anyone have a pic that they can post showing the location? If so, I'll add it on the '901 Transaxle Codes' tab of the Workbook.

Greg

[HAM Inc]

Scott thanks for the info. That's a pretty cool arrangement. Unfortunately SCCA requires we have a functioning reverse gear.
Len

[GTPatrick]

Race 914 ,

I tried several times to download your article but got a warning .

" Microsoft Word 97 Conversion " - Unable to load graphics conversion filter . Continue with document conversion .

1) what is a graphics conversion filter ?
2) what does this warning mean ?

I tried several times clicking on the yes and nadda . But on the 6th click a window opened up titled " Regearing - 080120 [1] - Word Pad " . This small article referred to a " 914 901 gear ratio work book " .

Was that article the workbook or is there another download available ? My PC has 2.66ghz and is about 3 years old so it isn't quite obsolete quite yet .

Thanks for any feed back on this one .

GTP

[race914]

Race 914 ,

I tried several times to download your article but got a warning .

" Microsoft Word 97 Conversion " - Unable to load graphics conversion filter . Continue with document conversion .

1) what is a graphics conversion filter ?
2) what does this warning mean ?

I tried several times clicking on the yes and nadda . But on the 6th click a window opened up titled " Regearing - 080120 [1] - Word Pad " . This small article referred to a " 914 901 gear ratio work book " .

Was that article the workbook or is there another download available ? My PC has 2.66ghz and is about 3 years old so it isn't quite obsolete quite yet .

Thanks for any feed back on this one .

GTP

The article is MS Word 97 and includes the workbook which is an MS Excel 2007 file.

I can't be certain, but from your info above, it sounds like your system may be trying to open the article in Word Pad?

You might try clicking the article link again, and then instead of clicking 'open', 'save' the document file on your system, then launch MS Word and open the article from there.


EDIT 1/22: If you don't have Microsoft Word or Excel here is a 'free' option:

Microsoft provides downloads for a Word Viewer & Excel Viewer

This post has been edited by race914: Jan 22 2008, 01:31 PM

[Gint]

The article is MS Word 97 and includes the workbook which is an MS Excel 2007 file.

I can't be certain, but from your info above, it sounds like your system may be trying to open the article in Word Pad?

You might try clicking the article link again, and then instead of clicking 'open', 'save' the document file on your system, then launch MS Word and open the article from there.


EDIT 1/22: If you don't have Microsoft Word or Excel here is a 'free' option:

Microsoft provides downloads for a Word Viewer & Excel Viewer

I'll also add that Open Office is an excellent solution for both opening and editing MS Word and Excel docs. For free!

[PeeGreen 914]

So I tore open three boxes and found two with the same gear stacks and one that was way different. I still have the one in my 6 that I am not too sire what is in there and another that has AFMSX. I am going to be building one box that has AFKaSZd, but I'm not too sure what I am going to do with the other gears. I am going to build one backup box as soon as I know what all gears I have. I will keep you posted.

[tac27]

Can anyone explain what the 'gear codes' mean? For example, the 'A', 'I', 'N' or 'X'. Are these codes universal, are just for the 901?

My Dad and I are rebuilding a '72 4 cyl. We've increased the displacement to 2L and switched to carbs. I'm not sure what hp or torque it produces.

thanks for posting the excel file

Tim
Las Vegas

[race914]

Can anyone explain what the 'gear codes' mean? For example, the 'A', 'I', 'N' or 'X'. Are these codes universal, are just for the 901?

My Dad and I are rebuilding a '72 4 cyl. We've increased the displacement to 2L and switched to carbs. I'm not sure what hp or torque it produces.

thanks for posting the excel file

Tim
Las Vegas

Hi Tim,

The codes you mention are specific to the 901 and are used to designate the ratio of each gear set. The Tech Article listed in the first post of this thread talks about the gear codes, and also contains an excel spreadsheet (click on the '914 901 Gear Ratio Workbook' link, then go to the third tab or worksheet: '901 Gear Ratios _ RPM_MPH Table') that includes all 901 codes and their ratios.

The Tech Article can be accessed by the main header: '914 Info' ; 'Tech Articles' ; 'Re-gear your 914'. or click here

Greg

[tac27]

Thanks for the information, Greg, I'll work though that excel file.

I'm hoping that a 'custom' set-up will add just a bit more zip!

Regards,
Tim

[race914]

With Santa's help, I just finished gathering the parts for my Laguna Seca gear setup: 904 mainshaft with A-H-Ka-Q-V. Here's the chart from the Gear Ratio Workbook link in this thread.




The issue I'm working is turn 11 which leads onto the main straight. The stock F 2nd was too low, and my Ka 3rd was a little too high. The turn before the longest straight is the most important turn related to lap times, and I was probably losing a couple car lengths there when I'd lose my momentum in traffic, so this was my highest priority off season improvement.

The H second will let me take that turn around 4K rpm. The video of the the original setup A-F-Ka-Q-V is here. Will post the results once I get the upgrades done and get back to Laguna.

Thank you Santa! (IMG:style_emoticons/default/santa_smiley.gif) (IMG:style_emoticons/default/bye1.gif)

[J P Stein]

Here's my plan for autocross:
F, K.

[jrthomasec]

How can I get my top speed up. I dont race but would like to get my freeay rpm's down and a faster top speed