3.55 vs 3.73 ?

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Originally Posted By: lawnguy
Will a 3.90 ring and pinion fit in my truck? I know I mentioned earlier about going from my 3.55 to 3.73,but I think 3.90 might be they way to go as opposed to 4.10. I also have verified that my auto trans is the 40r7w

Please advise.


If it is a set for that diff it will.
 
I found these.

https://www.summitracing.com/int/parts/mgr-f888390/overview/

https://www.summitracing.com/int/parts/fms-m-4210-c3/overview/



Now....do I have to actually buy this? Kind of costly?

https://www.summitracing.com/int/parts/fms-m4209adptac




Originally Posted By: OVERKILL
Originally Posted By: lawnguy
Will a 3.90 ring and pinion fit in my truck? I know I mentioned earlier about going from my 3.55 to 3.73,but I think 3.90 might be they way to go as opposed to 4.10. I also have verified that my auto trans is the 40r7w

Please advise.


If it is a set for that diff it will.
 
Originally Posted By: lawnguy
I found these.

https://www.summitracing.com/int/parts/mgr-f888390/overview/

https://www.summitracing.com/int/parts/fms-m-4210-c3/overview/



Now....do I have to actually buy this? Kind of costly?

https://www.summitracing.com/int/parts/fms-m4209adptac




Originally Posted By: OVERKILL
Originally Posted By: lawnguy
Will a 3.90 ring and pinion fit in my truck? I know I mentioned earlier about going from my 3.55 to 3.73,but I think 3.90 might be they way to go as opposed to 4.10. I also have verified that my auto trans is the 40r7w

Please advise.


If it is a set for that diff it will.


You could probably have the dealer do the recalibration for less than that.

And yes, assuming you have an 8.8" out back, those will work.
 
I don't use dealers. I have a local mechanic who is Master certified. Dealers are priced way to high!
 
My truck has the H9 axle code. How do I know if it's an 8.8 ,or 9.75?
 
Originally Posted By: lawnguy
My truck has the H9 axle code. How do I know if it's an 8.8 ,or 9.75?


They look markedly different, but it would be on the tag on the pot.

Given your truck is a 2WD 4.6L, it probably has the 8.8.
 
Axle Code H9 is a 3.55 Limited Slip. Since you have a 4.6 V8, you get the 8.8" axle. (5.4 equipped trucks get the 9.75).

If in doubt, count the bolts on the axle cover. 10 bolts is an 8.8, 12 bolts is a 9.75 on that generation of F150.

You can also look at the tags on the differential cover if they are still there. It will have a 8 8 for the 8.8 or 9 75 for the 9.75 axle in the codes (along with the gear ratio, limited slip, and other info)

On the speedo recalibration, your dealer can do it for way cheaper than the price of the part you posted (which doesn't include the install in its price). Otherwise, find a good 4 wheel drive or driveline shop to do it. Odds are your cheaper independent mechanic isn't equipped for this one. When I redid tire sizes on my F150 of that generation, the dealer did the reprogramming for less than $100.
 
I called my local ford dealer this evening. The lady I spoke with told me that their hourly labor rate was $119 hr ,and that it would take 8 hrs to remove my 3.55,and install new ring and pinion gears.
 
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You'd do well at an independent shop... one that does hot rods or even RVs/ big rigs.
 
Originally Posted By: lawnguy
I called my local ford dealer this evening. The lady I spoke with told me that their hourly labor rate was $119 hr ,and that it would take 8 hrs to remove my 3.55,and install new ring and pinion gears.
At that rate you can buy another F150

Find a driveline shop
 
Originally Posted By: lawnguy
I called my local ford dealer this evening. The lady I spoke with told me that their hourly labor rate was $119 hr ,and that it would take 8 hrs to remove my 3.55,and install new ring and pinion gears.


Yeee hawww!

I'd only take it to the dealer for the speedo recalibration. Find a driveline place as others have suggested to have the actual install done.
 
Originally Posted By: OVERKILL


I'd only take it to the dealer for the speedo recalibration. Find a driveline place as others have suggested to have the actual install done.


This. I believe this is what nearly all the advice in this thread has suggested.

In other words, use the shops for what they are good and qualified for.
 
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