250/350 rear end difference?

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Aug 13, 2004 | 02:21 PM

#16

FortyFords

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From: USA

RRMIKE,The speed will be off because the ring gear will spin faster or slower due to gear change .The tone wheel mounts to the ring gear.
I believe the auto shift points are recvd fron this also ! along with other sensors with the PCM.
Dealers can calibrate for you,even though they say they cant

Rich

Aug 13, 2004 | 02:42 PM

#17

CmprSpecial

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Joined: Jun 2001

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From: Northern Va

Quote:

Originally Posted by FortyFords

Regardless of ratio, the ring gear spins at the same rpm as the tires. The drive shaft rpm will change with a change in ratio, but not the ring gear. Change the tires, and the speedo will have to be recalibrated (easy on a Ford, it's electronic). Change the ratio and as far as the speedo goes, it knows no difference.

Since the engine RPM will be affected by the change, the transmission will shift funny for a while, but Fords adaptive shift strategy will adjust automatically over time.

Aug 13, 2004 | 02:48 PM

#18

Monsta

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Joined: Oct 2001

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From: Washington State

Quote:

Originally Posted by RRMike

I think you can put whatever gears you want in there without calibrating anything.

We had this "debate" a year or so ago.

I always thought that you could just pop in new gear, keep the tires the same and the computer would know no difference.

I was determined later that a few guys that changed the gears and nothing else, still had to let the computer know what gears it was runnin'.

Could be wrong...I'm just postin' off memory.

Aug 13, 2004 | 03:34 PM

#19

hang10

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I talked to the parts guy again, he found the 4.30s for the correct axles. I am going to look at other sources though. When he told me the ring and pinions alone were over $950.00 for the axle pair and their service dept told me a "minumum" 6 hrs per axle to do the work, about another $1,200.00, I think I will look elsewhere or just forget it.

Aug 13, 2004 | 06:08 PM

#20

RRMike

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From: Roseburg OR.

Quote:

Originally Posted by FortyFords

Sorry guys but the tone ring mounts between the carrier and the ring gear and spins the same speed as the carrier (and ring gear) which spins the same speed as the axles which spin the same speed as the tires. Put any gears you want in there and it aint gonna change. You can recalibrate for tire size but not gear change.

Rich,
Think about it this way: You say the ring gear will be turning faster or slower. In this case it'll be turning slower in relation to the trannie but that difference doesn't matter because the trannie doesn't determine your speed. The ring gear will be turning exactly the same in relation to the tires 1:1. The tires determine your speed.

If anyone can show me how the tone ring can turn at a different rate than the back tires (other than during a burnout

) I'll re-think my position but I don't see how it's possible.

Aug 13, 2004 | 06:25 PM

#21

DCSpecial

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From: IL, USA

hang10,
When I was calling most of the bigger drivetrain places and local dealers I found the best price on 4.30 gears from West Coast Differentials ( www.differentials.com or 800-474-4998), I spoke with Mike at ext. 110 if that helps any. And that was on Dana front gears and Ford rear gears along with install kits.

I agree with RRMike, the tone ring is going to spin the same speed as the rear tires.