Speedo Gears???

[Rod]

Finally got around and changed the speedo gear. The original gear was a 23 tooth gear and I have replaced it with a 22 tooth gear.

From what I have ascertained this gear has adjusted the speed to within one or two km/h for the 3.55 using another car as a guide. Tried to use the speed detectors out on the highway but for some reason it would not register. I tried numerous times; possible the ute is not a large enough object to detect.

Following on from Ken I assume that the new 22 tooth gear is from a FX / FJ. So for anyone who wants to agjust the speed with a 3.55 diff the 22 tooth is awfully close. Hope its of interest.

Rod

[FEHOLDEN]

GIDDAY EVERYBODY

JUST THOUGHT I WOULD RESURRECT THIS STRING BECAUSE I AM PLANNING TO FIT A 2.78 DIFF TO THE HT MANUAL WHICH I AM CURRENTLY DRIVING UNTIL "EFFIE" FINALLY SEES THE LIGHT OF DAY. NOT SURE WHAT CURRENT DIFF RATIO IS BUT HAS A RED GEAR GOING INTO THE BOX[3SP ALL SYNC]. IS IT AS SIMPLE AS JUST FINDING THE RIGHT GEAR? IF SO WHERE DO I START BECAUSE INITIAL ENQUIRIES FROM PARTS SUPPLIERS HAVE DRAWN A BLANK.IS GETTING IT CALIBRATED THE GO? IF SO WHERE?[I AM SITUATED IN DANDENONG RANGES]

ANY HELP WOULD BE MUCH APPRECIATED


DENIS

[EJ_Dave]

Denis,

if you can check your current diff ratio and the number of teeth on the red speedo gear I should be able to work it out. The diff ratio should be stamped on the flange attached to the yoke. I know the number of teeth on a red gear from a crash box but don't know if it is the same as in an all-synchro box. Does anyone else know if they are the same?

Also, is the speedo accurate with the current diff and speedo gear?

And are you sure you want to go to a 2.78? That's a pretty tall ratio with a 3 speed.

David

[FEHOLDEN]

gidday dave

thanks for the reply. i will get out and under the car tommorrow and let you know about diff ratio and teeth.

the speedo is currently accurate to within a bees genitalia so that should be a good starting point i suppose.

the 3 speed is only a short term thing as i also have an m20 ready to go in but not the time to do the whole job at once due to the daily driver status of the car.

thanks again


denis

[FEHOLDEN]

dave

diff ratio is 3.55 and red gear has 23 teeth. hope this helps.

thanks in anticipation


denis

[Effie C]

Denis

Following from HQ Spare Parts Book(Same Three Speed Box).

Diff Ratio       Tyre Size          Gear Colour       # Teeth
                 
3.08:1        F78-14                Pink            19
                 
3.08:1      All other tyre   White                20
                 
3.36:1      7.35 x 14            
     EB78S-14            
     195 x 14               Green            21
                 
3.36:1      6.95 x 14            
     185 x14            
     70 x 14             Dark Blue            22
                 
3.55:1      195 x 14            
     78 x 14             Dark Blue            22
                 
3.55:1      6.95 x 14            
     185 x 14            
     70 x 14            
     7.35 x 14                Red            23

Drive Gear Part Number 7437317


2.78:1 ratiois for Trimatic box


Diff Ratio      Tyre Size       Gear Colour       # Teeth
                 
2.78:1      F78-14            
     7.35 x 14               Pink              19
                 
2.78:1      6.95 x 14            
     185 x 14            
     70 x 14            
     7.35 x 14            
     1.95 x 14              White            20
                 
Drive Gear Part Number 5258493      

Hope the above helps
John M            

[EJ_Dave]

By my calculations you would need a gear with 18 teeth to give you the same speedo reading you have now. A 19 tooth (pink) gear may be the best you can do.

I worked this out by dividing 3.55 by 2.78 = 0.78. That is, your speedo will only read 78% of what it does now at the same actual speed. To correct the speedo you need a gear with 0.78 times the number of teeth you have now (23). This comes to 18. If you use a 19 tooth gear your speedo will read 5% lower than it does now. That is you will be going 5% faster than the speedo is telling you. This is not much but enough that you probably shouldn't allow yourself quite as much 'error' over the speed limit.

Good luck

David

PS. It sounds as though the speedo gears in the all synchro box may be the same as in the EJ-HK crash box- the tooth numbers are the same at least. Can anyone confirm or deny that they are the same?

[EJ_Dave]

Denis,

I understand the daily driver thing. All jobs on the EJ need to fit in with it's daily driver status.

Cheers,

David

[Effie C]

G'Day Denis
To follow upon what dave has said, to change from your red 23 tooth item to a pink 19 tooth would also require the changing of the drive gear in the gearbox (Different part numbers ) more than likely different number of teeth.
The other alternatives is to have a correction box made up by CRS or have your speedo re calibrated by a instrument tech.
Good Luck
John M

[FEHOLDEN]

gidday john and dave

thanks for your input. all i can say is that there are more champions on this site than you would find at an olympic games

i assume john you are talking about the internal gear in the box and not the plastic one on the end of the cable. sounds like a lot of work. may ring mr hadfield and suss him out about a correction box otherwise does any one know an approximate cost of callibration?

thanks again


denis

[Effie C]

G'Day Denis
Yep the drive gear is on the shaft within the rear extension housing, not really that hard to change. Just drop the rear housing off and it is held to the shaft with a spring type clip slide one off the other on and put extension housing back on.
Re calibration a lot easier but more expensive, not sure of cost but to have calibration checked and certified (required by rego and engineers) costs Approx. $180 in ACT.
John M

[FEHOLDEN]

ouch!!!sounds like i might be sounding out some parts suppliers and doing it myself.

thanks again


denis

[EJ_Dave]

Just thought I'd bring this thread to the top again because it answers some questions in the 'diff centres' thread just below. It seems that the FX-FJ gearboxes did have a different speedo gear to FE-EK- see Ken's reply (about 4th in thread- including part numbers!!). In an FC with a 3.55 diff and an FX-FJ speedo gear it seems the speedo reads pretty close to right. This assumes tyre diameters same as the originals.

David

[Phantom]

G'day all ,
                 What ratio diff did the LJ torana have and will this affect the speedo in my FC?
                                    Cheers Rusty

[craiga]

Rusty,

As per the Sydney Torana Club site here are the choices:

3.98:1 (4cyl 56bhp with four-speed manual).
4.125:1 (all other four-cylinder).
3.08:1, 3.36:1, 3.55:1 (six-cylinder) (LSD optional).

All of these diff centres will have an effect on your speedo reading, as will your wheel rim and tyre size.

Send me a P.M with your specs and I'll work it all out for you.

Cheers,

Craig.