Speedo Drive

[Guest art stringfellow]

HI folks I recently changed the gearbox in my 2B.Straight swop type 9 5 speed.I also swopped the speedo drive as I figured the old one was reading correctly.I now find the speedo is reading about 8 Mph slow.can anyone out there explain why.Will it be possible to change back.It looks a tricky job.Thanks Stringy

[Guest Ramraider]

Not 100% sure as its been a few years, but I belive the type 9 and several others to have a plastic worm gear just inside the the output for the speedo...these come in differant ratios and colours to correspond...have a look in your old gbox and gentle pull the worm drive out...Its probably a different ratio...HTH

[TonySuperSpec]

Not 100% sure as its been a few years, but I belive the type 9 and several others to have a plastic worm gear just inside the the output for the speedo...these come in differant ratios and colours to correspond...have a look in your old gbox and gentle pull the worm drive out...Its probably a different ratio...HTH

 

Yes the Type 9 and MT75 boxes were fitted to various vehicles with various diff ratios and Tyre sizes.

 

The idea of the drive gear is that it engages with a helical gear and can be made with various number of teeth to provide the correct spped for the cable.

 

Obtaining exact details of the gears is difficult, I had big problems just before SVA after the car was checked on a rolling road and the speedo was far to far out.

 

From what I found out 21,22,23,24 teeth gears are made (or were made for the boxes.)

 

I would try and extract the old one, it comes out by removing the cover bung and gently pressing the shaft end up I used a valve grinder suction type to then pull clear.

 

I was assured that any type 9 or MT75 gear fits any box !!

[Guest Ian & Carole]

HI folks I recently changed the gearbox in my 2B.Straight swop type 9 5 speed.I also swopped the speedo drive as I figured the old one was reading correctly.I now find the speedo is reading about 8 Mph slow.can anyone out there explain why.Will it be possible to change back.It looks a tricky job.Thanks Stringy

 

I seem to think that there were also two different steel gears on the output shaft.

 

So as you say you did swop your coloured plastic drive then the steel gear must be were the error has occured.

 

If you can get at it try and put the original drive from your new box back in.

 

Good luck with that one!!!!!!

[Guest klaxon]

I swapped from 3.38:1 to 3.92:1 Diff.

My speedo was reading 15% fast.

Ian is quite correct, there are two different steel worm gears, 7 tooth and 8 tooth.

There are quite a few different Diff ratios available and there is a correct combination of worm and gear for each one.

As there are two worms and four nylon gears to pick from, that gives quite a few possibilities.

I don't know if anyone has a list of diffs with required combinations.

I found the storesman at sandicliffe fords in Nottingham was very helpful. He identified the correct parts and was able to locate a new worm gear in Ireland.

Since the speedo drive is on the output shaft, the worm and gear from your old gearbox should be right providing you have not changed the Diff.

It's a major job to change the worm (extra long pullers required) but if you want it right, you have to do it.

I hope this is of some help.