Help needed with speedo cable drive
#1
Posted 03 January 2013 - 04:29 PM
I have been sitting back since joining the forum, reading and studying where and what I can. When I bought my LX I knew it was a bit of a mystery bag so it is a slow process of discovery. The speedo runs about 20kph above the actual road speed, so I would like to change the speedo cable drive gear accordingly. From what I can tell, I have a T5 gearbox (5 speed) which is mated to a VN efi V8, although if someone can confirm based on the photos it would be appreciated.
I have contacted Holden to ask for the price of a speedo cable gear and they keep telling me it is an electrical output, yet clearly mine has the gear drive!
Also from the photo you will see I have a 20 tooth gear drive. On the end of the drive it has the I.D.: 20A-CA.
The rear tyres are 265/50-15 and I am not sure of the diff ratio, I think it is 3.55? It is a 9" diff so where is the ratio shown?
From reading different posts and web sites, I understand my "driven" gear can be changed up or down 1 or 2 teeth without changing the driving gear on the output shaft (if that makes sense??) therefore I do not need to remove the rear housing from the gearbox. Looking at some supplier web sites, they refer to black (manual) and orange (auto) 20 tooth gears although mine seems brown???
So in summary, maybe you can help with the following list of questions:
1) Is it a T5?
2) If the speedo is reading high, do I need less teeth?
3) Can I just replace the cable gear shown in the photo or do I need to replace the mating ring gear on the output shaft?
4) Is the colour of the gear important or do I just count the teeth?
5) Is the diff ratio marked somewhere on the outside of the diff centre?
Thanks anyone for your help in advance!
#2
Posted 03 January 2013 - 05:28 PM
#3 _434LX_
Posted 03 January 2013 - 05:32 PM
4) The gears are usually colour coded (well the th350 ones are anyway). Have a look on the rare spares site as they sell various gears.
5) 9" generally do not have the ratio on the outside. You would have to drop the center and check out the gear set to get a definitive answer.
#4
Posted 03 January 2013 - 06:15 PM
So does anyone know if I need to change the internal gears or just the one in the picture? Thanks again.
#5
Posted 03 January 2013 - 07:05 PM
I have been through the same exercise in my LC (T700, 9 inch), spent heaps of time trying to locate the correct driven/drive gears. In the end opted for a $100 Garmin GPS and use it as my speedo (very accurate).
V6TORANA
#6
Posted 03 January 2013 - 08:18 PM
#7
Posted 03 January 2013 - 09:30 PM
Thanks everyone.
#8 _Emu_
Posted 03 January 2013 - 09:36 PM
Just take your gear off, head to rares or wherever and get one with more teeth (22 would drop it 10% I'd think so maybe 24 teeth is needed.) I am sure someone here will know. That gear looks the same as what Ford run in their autos out of 90's falcons....should be cheap as
#9
Posted 03 January 2013 - 09:57 PM
http://www.moderndri.../t5_history.htm
The following is an extract from the article about the Ford speedo drive gears.
1990 to 1993 the stock Ford production V-8 WC T-5 was upgraded with stronger 3.35 gear set by increasing the nickel content to produce a harder, stronger gear. 2nd and 3rd gear ratios were decreased slightly to provide more torque to the rear wheels. Synchro linings on 3rd & 4th were improved by changing from fiber linings to carbon fiber to further improve the friction surface resulting in better high rpm shifts. A longer throw shifter was installed to "make shifting easier". The speedo drive gear was changed from 7 tooth to 8 tooth. The 8 tooth was a step backwards when installing lower rear axle ratio greater than 3.55 as the driven gear is limited to 21tooth count. Yes, 23 tooth gears are available but do not last long as the teeth are thin and do not mesh correctly. Torque rating jumped to 300ft/lbs.
Edited by S pack, 03 January 2013 - 09:59 PM.
#10 _434LX_
#11
Posted 05 January 2013 - 02:14 PM
So I went for a drive yesterday with the GPS down the M4 motorway. I checked the speedo readings at 60, 80, 90, 100 and 110kph. Short term I might just mark the speedo cover with very small strips of white contact at the key speeds. The speedo is doing 155kph at 110 so the error increases with the speed. I also noticed the engine is super smooth at 80 although by 110 it is above its ideal cruising rpm's so I am going to work out the current ratio (I understand it is somewhere between 3.55 and 3.96?) and drop it down to get a more suitable highway rpm. Doing that will again change the speedo output and so best leave that problem until after the diff has been sorted.
Also I know it is a limited slip (the inside chirps if I am doing a u-turn, and I have tested the sideways abilities just once.....) although I do not know if it is a mini spool or what. Ahh the excitement of buying an unknown...!
#12
Posted 05 January 2013 - 02:46 PM
Jack one wheel off the ground and turn the wheel ten revolutions counting the number of tailshaft revolutions (make sure the other wheel does not turn). If the tailshaft turns 15.04 times then you have (15.04 * 2) / 10 = 3.08 centre.
LSD Centre
Jack both wheels off the ground and turn the one wheel ten revolutions counting the number of tailshaft revolutions (make sure that both wheels turn at the same speed). If the tailshaft turns 30.08 times then you have 30.08 / 10 = 3.08 centre.
You can also use string taped to the tailshaft to count the revolutions.
http://www.gmh-toran...showtopic=10732
You can fit a ratio box or drive joint to solve the speedo errors. Flexible Drive Agencies list the ratio boxes as drive joints. Flexible Drive Agencies make both standard speedo cables and a cable to suit the ratio box.
Method of Calculating Drive Joint Ratio
1. Drive vehicle on a measured course of ~ 5 km. The longer the course, the more accurate the test.
2. Note distance measured on the odometer.
3. The Drive Joint Ratio can then be calculated as follows:
Actual Distance Travelled / Odometer Reading = Drive Joint Ratio
If it turns out that you drove for 5 km and the odometer read 5.5 km then you would fit a 5/5.5 (0.9090) ratio drive joint.
Edited by dattoman, 05 January 2013 - 03:20 PM.
#13 _coupe202_
Posted 05 January 2013 - 07:36 PM
#14
Posted 05 January 2013 - 10:02 PM
Bernie
Edited by Bernie, 05 January 2013 - 10:06 PM.
#15 _pinklx_
Posted 07 January 2013 - 09:46 AM
so
1) yes its a t5
2) yes u need less teeth
3) no u can just change that gear
4)colour isnt realy important, differant makers use differant colours
5) the ratio isnt written on the outside of a 9"
Edited by pinklx, 07 January 2013 - 09:56 AM.
#16 _pinklx_
Posted 07 January 2013 - 10:02 AM
#17
Posted 07 January 2013 - 10:43 AM
I appreciate everyone's input and will let you know the results of the "string test".
#18
Posted 18 January 2013 - 09:55 PM
#19
Posted 20 January 2013 - 11:16 AM
So then my options are:
- Swap mine for a 2nd hand centre
- Do a rebuild with new gears myself
- Pay a shop to rebuild it with new gears
- Leave it as is.
#22 _nemo355v8_
Posted 21 January 2013 - 07:30 PM
Jump on ebay and gab for under $15
.
TKO 500/600 alo us the same cog.
The gear off electronic speed sensor off cars using a T5 will also fit, Im using a EA falcon Electronic speedo pick up cog on my cable in my hatck
Edited by nemo355v8, 21 January 2013 - 07:33 PM.
#23 _nemo355v8_
#24 _nemo355v8_
#25
Posted 21 January 2013 - 08:46 PM
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users