T50 / K50 gearbox – Speedo drive assembly

Description

T50 / K50 gearbox- Speedo drive assembly

A new Speedo drive housing and gear assembly to suit some of the K40 / K50 / T40 / T50 gearboxes. Please see the parts compatibility before purchase.

 

Parts supplied

– Speedo drive housing: Pre-fitted with the gear of choice.

– Retainer tab

– Retainer bolt

NOTE: For those who only wish to buy the gear / shaft combination or the housing alone then this is possible to do so for half of the advertised price. Use the comments box during the checkout to leave a note with the relevant request and then make the purchase with the full payment. When the order is packed and processed a partial refund will be manually made for the payment difference.

 

Part specifications

– Housing outer diameter: 22mm

– Thread size for speedo cable coupling: M22 x 1.5mm (Common to all Toyota mechanical speedos)

– Drive teeth: Fitted with either a 19-tooth (19:5) or 22-tooth (22:6) gear, these are the only two options that are still available new. All of the other variants have been discontinued by Toyota.

 

Parts options – See comparability notes also

– 19 Tooth gear to suit a 5 tooth internal gear only

– 22 Tooth gear to suit a 6 tooth internal gear only

 

Compatibility

– K40 / K50 Gearboxes: The available parts catalogs show that the speedo housing offered here was the type used on many models from early 1979 onwards. There are 3 or more different part numbers listed for the retainer tab, although these may well still be the same or be cross compatible. Lastly the 22:6 gear is also listed as being correct for multiple different but not all models.

– Due to the different internal gearbox variations available it is up to the customer to personally verify the part compatibility and the purchase is at their own risk.

– Internal gear type: There are at a minimum at least 2 different internal speedo gear drives used: 5 or 6 teeth. It is suggested to shine a light into the gearbox through the speedo drive hole and carefully count the amount of teeth this gear has. This can be done by rotating the output shaft 360 degrees or the input shaft with 4th gear engaged (for a 1:1 ratio) and then count how many of the gears teeth ends end up passing by, it will be either 5 or 6.

Below is a list of which internal gear the gearbox is likely to have depending on which diff ratio the car is / was fitted with. NOTE: This should be used as a guide only as it is no guarantee of being correct.

 

Diff ratio / Speedo gear : Internal drive gear

3.9:1 = 20:6 teeth

4.1:1 = 21:6 teeth

4.3:1 = Either 19:5 or 22:6 teeth – Confusingly either of these options could have been used with this diff ratio

 

If the car originally used a 3.9:1 or 4.1:1 ratio then the 22:6 gear option should be physically compatible. The resulting speed / readout will be wrong but this can be corrected (See next section).

 

Additional information

Speed correction: Physical gear compatibility aside there is the matter of if the speedometer is showing the correct reading. With half of the gear options discontinued the only way to adjust the drive reading to be correct if necessary is via an external speedo shaft correction box. All of Toyota RWD speedo’s have the same mechanical output, as such finding such a device is very easy, for example doing a search for a “Supra speedo correction box” which despite being intended for a completely different model of gearbox is still completely compatible, only the ratio of correction matters.