0-90mph in 1 second! - speedo problem!

[Matt Tomkins]

Hi all,

I've got an issue with my speedo.

It's started to judder around all over the place.
it started on monday going 0-90-0-90-0-90 etc - i put this down to a kink in the speedo cable.
having re-routed it three times i noticed it had dabbed on the hot manifold and the spring was jamming.

I ordered a replacement cable from ESM, which i fitted today.
This bounces all over the place. no pattern, treally - tries to go all the way around etc - even when only pulling away
when i reach about 40mph, it settles down, and displays the correct speed up to 75 (as fast as it'll go! :p)
when i wind her down again, though, it can get to about 15/20 before it starts jumping around all over the place again.

I've re-routed the new cable, and tried to get as subtle a curve as possible into it.
I've also removed and greased the internal spring.
all to no avail.

I really need to hget it sorted ASAP - i have an advanced driving course it her next wednesday, and a policeman in the passenger seat
I just want everything to be 100% legal and perfect!

Any suggestions would be greatly appreciated.

thanks again, so much

matt

[bmcecosse]

Can only suggest the initial bouncing from the 'fried' cable has damaged the speedo spring..... Did you fit a complete new cable - or just a new inner??

[mike.perry]

Beg, steal or borrow a new speedo head with the same TPM for your test and the best of luck

[Matt Tomkins]

Can only suggest the initial bouncing from the 'fried' cable has damaged the speedo spring..... Did you fit a complete new cable - or just a new inner??

Complete new cable. :/

Can the speedo itself be opened up and oiled with something like 3 in 1?

Beg, steal or borrow a new speedo head with the same TPM for your test and the best of luck

What do you mean by tpm?

Many ta

Matt

[Matt Tomkins]

Can only suggest the initial bouncing from the 'fried' cable has damaged the speedo spring..... Did you fit a complete new cable - or just a new inner??

Complete new cable. :/

Can the speedo itself be opened up and oiled with something like 3 in 1?

Beg, steal or borrow a new speedo head with the same TPM for your test and the best of luck

What do you mean by tpm?

Many ta

Matt

[Matt Tomkins]

Can only suggest the initial bouncing from the 'fried' cable has damaged the speedo spring..... Did you fit a complete new cable - or just a new inner??

Complete new cable. :/

Can the speedo itself be opened up and oiled with something like 3 in 1?

Beg, steal or borrow a new speedo head with the same TPM for your test and the best of luck

What do you mean by tpm?

Many ta

Matt

[chrisryder]

tpm = turns per mile. there will be a small code written on the face of the speedo. usually preffixed by 'SN' if i recall.

no amount of oiling can fix a damaged spring i fear.

[Matt Tomkins]

tpm = turns per mile. there will be a small code written on the face of the speedo. usually preffixed by 'SN' if i recall.

no amount of oiling can fix a damaged spring i fear.

Which is/ where is the spring you are referring to?

[beero]

You can test the speedo with the old cable and an electric drill (in reverse I think)

[Matt Tomkins]

You can test the speedo with the old cable and an electric drill (in reverse I think)

how fast should the drill go? - full wack for a 10mph reading, or dead slow for 50?

does anyone have a diagram of 1) the insides of the speedo and/or 2) the wiring to the back of the speedo?
i can't seem to find either in my manuals :/

thanks again

[bmcecosse]

It's a very very light spring inside the speedo.......

[Matt Tomkins]

It's a very very light spring inside the speedo.......

replacement job, then :/

also, where on the speedo is the tpm?[frame][/frame]

[MColes]

[frame][/frame]


I believe it should say 1408

[beero]

how fast should the drill go? - full wack for a 10mph reading, or dead slow for 50?

I meant for you to test if the needle is steady when the drill speed is steady.
If you have an adjustable speed drill the speedo will show faster as the drill speed increases.

[mike.perry]

There are a lot of double postings can you delete them?
TPM = turns per mile, 4 fig number after the serial number on the speedo face, normally 1408 for 1098/4.22 diff, 1504 for 948/4.55 diff.

[bmcecosse]

And 1248 for the 3.7 final drive.

[Declan_Burns]

You can see it clearly here.[frame][/frame]


[frame][/frame]
Regards
Declan

[chrisryder]

After all of this TPM talk, i looked at my speedo (1098 67 4 door, standard drivetrain) at it has '1376' as its TPM.

Any idea why someone would have fitted a 1376? it doesn't sound that far off 1408. Based on the TPM being higher for higher diff ratios, i'm guessing lower would relate to lower diff ratios. But the gap between 4.22 and 4.55 diff TPMs is almost 100. and mine's only 32 different. could it have been for the hallowed 4.1 diff? or could someone have chosen to fit it to correct the gearing if slightly larger wheels were fitted? I'm flumoxed!

i did change diffs ages ago for 'another' 4.2 (as i thought the old one was noisy) but i don't recall checking to see what ratio came out. i may have to dig it out to make sure it's not a funny ratio!

[mike.perry]

Maybe the original speedo was knackered and the owner did not know the difference. Have you checked the accuracy?

[chrisryder]

yes. 10% high with my small wheels!

i'm fitting a 3.9 diff during the week, that may make up the difference!

the speedo doesn't really bother me, so long as i know how innaccurate it is i've been able to recalibrate my brain for the last 3 years!