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Old 12-12-2003, 02:10   #1 (permalink)
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Do i need to change anything on auto if changing diff to 3.7

Im thinking of putting a 3.7 diff ratio in my car but a while back when i was thinking of doing it i think somebody said i had to change something in the auto or change the chip because the engine may cut out or somthing because of the high revs.

any advice would be great.
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Old 12-12-2003, 21:10   #2 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

What car?
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Old 12-13-2003, 05:19   #3 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

Only drive gear on speedo at the end of speedo senser/ sender...
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Old 12-15-2003, 05:15   #4 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

yeah - as long as the speedometer reads correctly the auto will work fine.
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Old 12-15-2003, 22:48   #5 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

Sorry guys its a ef fairmont 6cldr.

Any idea what it should cost? part plus instalation??

Thanks
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Old 12-17-2003, 14:16   #6 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

Gears + install probably arround $750.

Ford's lowest speed sensor is for the 3.45 diff. You will need a speedo matching magic box to correct the spedo.

Also regarding the computer, if you get a new sender worked out your box will be happy but the lockup points will remain the same. A chip could revise the locup points to occour at a lower speed to compensate for the increase in RPM.
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Old 12-18-2003, 00:15   #7 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

thanks walkinshaw,
Regarding speedo matching magic box do u no the cost of one and installation price.


And about getting a chip for computer in trans to change lock up points(is that the gear change points??), would it be more effective than not doing it??(ie better in 1/4 mile)

So if i dont change the chip dose that mean the engine will rev out to a higher rpm??? little concerned as i may blow engine.
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Old 12-19-2003, 05:22   #8 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

the rev limiter will still work at the exact same rpm as it did before - you will not blow your engine.

and im not sure what walkinshaw means?
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Old 12-19-2003, 21:51   #9 (permalink)
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Re: Do i need to change anything on auto if changing diff to 3.7

Those speedo correction boxes are worth about $200 for the VDO, and castlemaine rod shop sell one for around the $300 mark??

If anyone knows who can make custom sender gears PLEASE TELL!
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