T50 Speedo Gear Problem

[Mickoolz]

Hey guys just wondering if anyone can help me out. My speedo stopped working a little while back so my brother and I pulled out the drive gear and low and behold the nylon gear was chewed up in the middle, like a half moon shape. So we replaced it with the same gear. It only lasted a week, if that, and is chewed again. After doing a little bit of research I'm lead to believe it may be the wrong speedo worm drive ratio. Is it possible to tell how to figure out the correct speedo worm drive ratio just by looking at the worm gear or is it a matter of pulling the worm gear out and matching it to the drive gear???

 

I'm lead to believe there a few different ratios as such 5 x 19, 6 x 20, 6 x 22 meaning 5 starts on the worm gear and 19 teeth on the drive gear etc....

 

My drive gear had 20 and 9, or was it a 6, embossed on the end of the gear.

 

Any help would be much appreciated :lol:

[parrot]

The drive and worm can be independently changed. The gear being chewed is more likely due to the fact that the metal worm gear within the extension housing will turn no matter what, and if the gear gets jammed somehow, being plastic it will get chewed. It's the safety valve if you like.

 

I would imagine you have either a buggered speedo cable (or you have bent it to far on itself) and it is jamming up, or less likely the speedo has seized.

[Mickoolz]

The drive and worm can be independently changed. The gear being chewed is more likely due to the fact that the metal worm gear within the extension housing will turn no matter what, and if the gear gets jammed somehow, being plastic it will get chewed. It's the safety valve if you like.

 

I would imagine you have either a buggered speedo cable (or you have bent it to far on itself) and it is jamming up, or less likely the speedo has seized.

 

Thanks for the info dude. My cable seemed to flow freely when I had it out and to what I thought it had no tight bends in it. One thing I did notice tho was when we had the gearbox out the speedo seemed a little loose when it was bolted on. I'm not sure how tight they're suppose to be in the housing but do you think if there is too much movement that it's a possibility the gear could jam and get chewed?

[parrot]

The speedo drive has a little tab that holds its housing in place in the extension housing (secured by a bolt). If that isn't there the drive housing could fall out, but I can't see how that would mash the plastic gear, as the plastic gear wouldn't mesh anyway. The speedo drive is a snug fit inside its housing so don't see how it could be loose?

[Mickoolz]

The speedo drive has a little tab that holds its housing in place in the extension housing (secured by a bolt). If that isn't there the drive housing could fall out, but I can't see how that would mash the plastic gear, as the plastic gear wouldn't mesh anyway. The speedo drive is a snug fit inside its housing so don't see how it could be loose?

 

Yeah the tab and bolt are in place n it just feels a little wobbly. I dunno, maybe it's the wrong gear. Might have to take it to the pro's to get it sussed out. Thanks heaps for the help mate :P

[Jonny Rochester]

One problem is the metal worm drive gear on the output shaft gets rusty, then the rust eats out the plastic gear.

 

I had this once on a completely stock and otherwise healthy car. The car was an import and had sat on the warf for a while, meaning the metal gear could rust. I fixed it with a new metal gear from Toyota, but could also have fixed it by sanding off the rust.

 

If you want to know the ratios and number of teeth etc, I can look that up but it takes a bit of time.

 

For T50 gearbox, there are 2 different sizes of gear sets (not just the ratios) due to the different size output shaft on the gearbox. The change comes half way in the TE72 range. The old style has the metal gear just slip onto the output shaft, located by a ball bearing. The newer sort (late TE72 and AE86) has the metal gear with a spline that matches the output shaft spline.