Sva 2nd Retest

[Guest Friar Tuck]

Chris

 

I checked the plate in the diff and it says 3.92, I also checked with both wheels rotating, and it is 3.92 !

 

Are you saying that I need to change the speedo driven gear to one with more teeth?

 

I have looked at this so many times, and get more and more confused each time I try and do some calculations.

 

If the yellow gear supplied has 26 teeth, I think that I need to have more teeth on this driven gear to slow down the cable, and thus slow down the speedo.

 

Are there any Super Spec builders who can confirm the number of teeth on the yellow driven gear supplied , before they fit it please ?

 

Cheers

 

The Friar

[Guest bugsy]

isn't it about time Bugsy sorted himself out and got his finished?

Dont bloody start Friar!!!

 

I don't suppose you have contacted Richard, have you Paul ??

No!! me and Richard seem to have different opinions on some SVA issues which i feel are important, i will sort my own problems out from now on! :gdit:

 

So many excuses

I have plenty more where that came from

Bugsy

Ps remember Friar, make sure the car is not in gear when you try to start the engine

[Guest Friar Tuck]

I didn't really want that to come out thank you Bugsy !!!

 

Has anyone got a spare rear mudguard for a Suzuki VL1500 please ?

 

Answers on a postcard to :-

 

Tuck

[Guest Dredd]

I have a spare yellow drive. It has 22 teeth.

[Mitch]

Ammo for Bill there Bugsy,

 

friar tuck may have to be renamed to LURCH

[Guest Friar Tuck]

Mitch

 

Why Lurch? Have you been looking at pictures again? It wasn't me honest !!

 

Dredd

 

Thanks for that info, all I need to do now is work out how many teeth we need to slow it down the right amount.

 

Watch this space

 

Tuck

[Mitch]

if left in gear, i presume it LURCHED forward into the Suzuki

[Guest Friar Tuck]

No it didn't lurch at all, it drove itself about 13 feet and hit the Suzuki quite hard actually!!! :gdit:

 

That was with two of us hanging on for all we were worth, but it just wasn't going to stop !!!

 

From now on, I will only start it when sitting in the car with my foot on the clutch, and even then after checking more thoroughly that it is in neutral!

 

Oh what the hell? !, I have been insulted by professionals, so nothing you can say will hurt now !!!

 

 

Stick and stones !!!

 

Tuck

[Guest chris brown]

I have a spare yellow drive. It has 22 teeth

Unfortunately I don’t think its as simple as changing the drive to the spedo I think you would have to change both gears at the same time. This to me seems to be a RHSC problem where they have just heaped up gear boxes in one place and rear axels in another with no thought to matching them up.

At the end of the day it would be simpler to change the dif for a longer legged one (3.6? can’t remember the actual ratio but it increases speed in gears by about 10% Salty has one fitted which he is hoping to replace with a 3.92)

[Peter Bell]

Chris I think you are right I can't see that you can just replace 1 gear as the diameters will be different! To get it right by changing the diff it will need something like a 3.25:1 ratio. An option is to get a gearbox made for the speedo cable somewhere about 1:1.2 to slow the cable down, I think that Speedy Cables do that sort of thing.

Peter

[Guest Friar Tuck]

Chris and Peter

 

I have done some calculations, taking in to account the margin of error, which is 20% at indicated 35mph, 25% at 40mph, 22% at 50 and 60%, and 20% at 27%, and if the number of teeth on the yellow gear is 22, then a driven gear with 26 teeth will give me accurate readings to within 1.8mph maximum tolerance.

An increase to 27 teeth would take the speedo readin below the actual road speed, at certain points, which of course could have some repercussions.

 

I am sorry to say that I do not follow the logic of changing the diff, and cannot see how it could possibly be simpler than changing the driven gear in the gearbox, which is effectively just one bolt to remove the cover, extract the gear, inssert the new gear and replace the cover, oil seal and bolt.

 

Ford make a number of different gears to suit the MT75 gearbox, I am sure that I just need to get confirmation of what colour the 26 tooth gear is, and away I go.

 

If I am totally wrong, could you please explain why you are advocating changing the diff.

 

Thanks

 

Tuck

[will]

Well done Friar!!!!!

 

Sorry for not congratulating you sooner I've been at CentreParcs for a week relaxing with the family.

 

It's fantastic news and a great boost to know that one day my collection of nuts and bolts will come together to produce a road legal car!! (even if the speedo doesn't work!!)

 

All the best

 

 

Will

[Guest Dredd]

I agree Friar, the speedo is driven by the final drive from the gearbox, so how can the diff effect it? Surely following that logic, the sppedo would be inaccuarate if the wheel diameter were changed. Now I'm not an engineer or machanic, just a simple public servant so I am sure I will be corrected. Anyway, plates are on and maiden legal voyage tomorrow!

[Guest chris brown]

Friar sorry if peter and I are confusing you but hear goes I will try to explain.

1/ The spedo drive gear mates up to a second gear inside the box therefore if you change the output one (the one which is effectively connected to the spedo cable) to a different number of teeth then you would have to change the internal one as well unless they would not mesh correctly.

2/ Replacing the dif for one with higher ratio would mean that for each revolution of the output shaft of the gearbox the car would travel further but the spedo would read the same as previous as all it reads is gearbox output speed not road speed.

Hope this helps

 

Dredd

Surely following that logic, the sppedo would be inaccuarate if the wheel diameter were changed

You are correct if you change the size of your road wheels your spedo will alter try link to see by how much Tyre size calc Edited October 8, 2004 by chris brown

[Guest Friar Tuck]

Chris and Peter

 

I think I understand what you are saying, but the idea of changing the diff is just too drastic in my opinion.

 

If that is the only way to sort out the speedo issue, why do Ford make all of these different coloured driven gears?

 

As far as my understanding goes, the actual 7 tooth drive gear is a worm type gear, surely that solves the issue of meshing with a driven gear with more or less teeth.

 

Correct me if I am wrong.

 

Friar Tuck