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Old 04-16-2021, 03:01 AM   #1
Mr.Borrie
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Default Speedometer 200+ @50

When I’m going perhaps 50/70KM per hour the dash tells me its going 200/220 and jumping needle. I think the car has got a locker from a 940 bolted on it so perhaps different sensor needed? It's a 1986 745 B230FK + M90 swap build in a barn type of Volvo I bought few months back.

It has a ton of **** done to it I have no clue about yet (wires, gauges etc everywhere) had not created a build page for it here yet cause I was going to flip it.. but I might keep it
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Old 04-16-2021, 03:30 AM   #2
MasterBlaster
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Generally, a non-turbo, non-ABS diff will have a 12-slot tone ring.
Add ABS, the ring goes to 48 slots.
(I hear one year even had 96!)
48 / 12 = 4
50KM * 4 = 200KM

Looks like your 12-slot-programmed speedo (1986 745) is getting too many pulses from your (apparently) 48-slot diff.

You need either:
1 - Different diff with 12 slots to match the speedo.
2 - Different speedo to match the current diff.
3 - Modify the tone ring from 48 to 12 slots.
4 - Replace the tone ring with a 12-slot.







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Last edited by MasterBlaster; 04-16-2021 at 03:38 AM..
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Old 04-16-2021, 03:45 AM   #3
Swedbrick
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I've had this issue as well and made this little board for it, it converts the 48t to the 12t signal and has a port for the lh2.4 tacho input from the 48t still as it requires it for the decelleration to work. I have a few still, I ordered parts for 5, so feel free to pm me;)

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Old 04-16-2021, 12:54 PM   #4
Khrrck
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Quote:
Originally Posted by Swedbrick View Post
I've had this issue as well and made this little board for it, it converts the 48t to the 12t signal and has a port for the lh2.4 tacho input from the 48t still as it requires it for the decelleration to work. I have a few still, I ordered parts for 5, so feel free to pm me;)

Hah! Glad someone else thought of a pulse divider. Even has DIP switches for adjustment it seems. Very clean.
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Old 04-16-2021, 04:14 PM   #5
2manyturbos
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There is only one instrument cluster that will correct the problem. A 1990 740 cluster from an ABS car will fit your dash and read correctly with a slight re-wire job. That circuit board seems like the easiest/cleanest solution to me.
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Old 04-16-2021, 06:15 PM   #6
Swedbrick
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Quote:
Originally Posted by Khrrck View Post
Hah! Glad someone else thought of a pulse divider. Even has DIP switches for adjustment it seems. Very clean.
Yes indeed, it has a simple VR setup with a divider, nothing fancy, just very tiny
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Old 04-17-2021, 03:55 AM   #7
Mr.Borrie
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Quote:
Originally Posted by Swedbrick View Post
I've had this issue as well and made this little board for it, it converts the 48t to the 12t signal and has a port for the lh2.4 tacho input from the 48t still as it requires it for the decelleration to work. I have a few still, I ordered parts for 5, so feel free to pm me;)

I love stuff that solves things , PM incoming.
Hoping shipping from grolsch country isnt to bad
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