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Discussion Starter #1
I've searched but I don't think I'm using the correct phrasing or words...

My buddy has a set of 4.10s with really LOW mileage on them that he pulled out of his Mustang. From what I've been able to find, these will work fine in my Bird correct?

And if that is correct, what other parts will I need to source other than a new speedo gear and a tune? Will I be forced to change my driveshaft and do a forced lube setup on the tail shaft of the tranny? I know I will definitely have to change the shaft if I plan on exceeding upper 80s/lower 90s.

He is giving me a great deal on these gears and I don't want them just sitting around going to waste while I gather other parts that I don't ABSOLUTELY need.
 

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The gears are all universal on all 8.8 differential cars. Mustang, Thunderbird, MkVIII, Cougar, F150, etc. On the other hand the differential is not universal, you need a 28 spline IRS compatible carrier.

The problem with the driveshaft is that as it spins it becomes less stable. It will eventually reach critical rotation and will bow and break eventually. You will notice vibration around 70 mph so, by 80 it will become unbearably loud. Continued driving like this will cause rear seal damage on the transmission and you will more than likely leak ATF.

You will need the driveshaft, but a forced lube set up will not be required. Also while your there, find yourself a LSD differential and install it. That is if you weren't one of the lucky few to attain the 3.27 TL option on your car.
 

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Discussion Starter #4
Stay Unique - My car did come equipped with the 3.27 TL unit. So basically all I'll need to effectively run this in addition to the speedo gear is a new driveshaft? That sucks... time to start looking for an aluminum Mark shaft I guess.

Coggonobrien - My current BFG KDWs in 245/45/18 seem to be plenty sticky enough with the 3.27s. They'll probably shred exactly like I want them to with 4.10s. But in long term I plan on switching to 275s or 285s in the rear to help fill out the fender well a little more.
 

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Stay Unique - My car did come equipped with the 3.27 TL unit. So basically all I'll need to effectively run this in addition to the speedo gear is a new driveshaft? That sucks... time to start looking for an aluminum Mark shaft I guess.
No, It is correct that you will need a new driveshaft, but you can not just swap the speedo gear, the PCM only corrects up to 2 steps up. So with 3.27's the highest you can go is 3.73's without a retune. Also the most important thing is not to run the 4.10 gear speedo gear, it will tear itself to pieces inside the tailshaft housing and junk your transmission from what I've read.

In order to run anything higher then 3.73's you will need:

1) A better 1 piece driveshaft, professionally balanced with new u-joints

2) A tune so your car doesn't top out at 90

3) A speedometer correction device such as a dallas speedcal (good luck with the actual settings)
 

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If you do the gear swap and don't do the tune, will the engine hit the limiter before it knows to upshift? Assuming you were hard enough into the throttle for this to happen.
 

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I've searched but I don't think I'm using the correct phrasing or words...

My buddy has a set of 4.10s with really LOW mileage on them that he pulled out of his Mustang. From what I've been able to find, these will work fine in my Bird correct?

And if that is correct, what other parts will I need to source other than a new speedo gear and a tune? Will I be forced to change my driveshaft and do a forced lube setup on the tail shaft of the tranny? I know I will definitely have to change the shaft if I plan on exceeding upper 80s/lower 90s.

He is giving me a great deal on these gears and I don't want them just sitting around going to waste while I gather other parts that I don't ABSOLUTELY need.
You will also need new pinion bearings, seal, crush sleeve, a few pinion shims and some other miscellaneous stuff. You will also need access to a press. From what I have read as long as you are reusing your differential then a gear swap is very trivial and should not require much if any shimming to get the proper patterns. I am curious myself to hear about how 4.10s work in a street driven tbird. I was just thinking the other day that gears might be a good upgrade.

Will
 

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Dew The Thunder,

Also just so you know NO 4.6 Thunderbirds came from the factory with TL. Or they would have to order it that way.

To get TL a buyer would have to request it.

If you have a TL unit then someone swapped in the diff.

Look at the tag on the diff it will have a TL on it.
 

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Dew The Thunder,

Also just so you know NO 4.6 Thunderbirds came from the factory with TL. If you have a TL unit then someone swapped in the diff.
AFAIK No Mark VIII's came with a TL, but TL's were an available option for many Thunderbirds/Cougars. :thumbsup:
 

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Dew The Thunder,

Also just so you know NO 4.6 Thunderbirds came from the factory with TL. Or they ordered it that way.
If you have a TL unit then someone swapped in the diff.

Look at the tag on the diff it will have a TL on it.
Trac-Lok was a factory installed option.
 

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Dew The Thunder,

Also just so you know NO 4.6 Thunderbirds came from the factory with TL. Or they ordered it that way.
If you have a TL unit then someone swapped in the diff.

Look at the tag on the diff it will have a TL on it.
My 97 came with a 3.27 TL rear straight from the factory, and nearly every SC ever built also had a TL, if not all of them. The above information is not at all correct with the exception of the tag. If it is a original to the pumpkin and it is equipped with TL it will read something like 3 L 27 or whatever gear is in there, or 3 27 if no TL is in there, the space between the numbers designates it as an open rear end. From what I recall, you could have 2.73, 3.08 or 3.27 from the factory in either TL or open, and the Mark VIII's came with a 3.07 open rear and as far I as know that was the only option.
 

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My 97 came with a 3.27 TL rear straight from the factory, and nearly every SC ever built also had a TL, if not all of them. The above information is not at all correct with the exception of the tag. If it is a original to the pumpkin and it is equipped with TL it will read something like 3 L 27 or whatever gear is in there, or 3 27 if no TL is in there, the space between the numbers designates it as an open rear end. From what I recall, you could have 2.73, 3.08 or 3.27 3.31's were also available from the factory in either TL or open, and the Mark VIII's came with a 3.07 open rear and as far I as know that was the only option LSC's came with Open/3.27's.
:)...
 

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My 96 Tbird had all the options except for TA and ABS.

But it still did not have TL. Just 3.27 open diff.
 

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Discussion Starter #18
I'm fairly sure the only two options my car did not have from the factory is TA and Premium Sound.

Really all I need to know is exactly what parts I will need to acquire before I take this car to a shop and they look at me with a stupid expression wondering why I want 4.10s in a Thunderbird.

Will - I will be having a shop do the installation as this is not something that I am qualified to do nor do I have the time to do it myself. My friend, whom I am acquiring the gear set from, said that I can buy a installation kit of some kind that includes all those wear parts and the shims. Hopefully I can have this done by the end of summer but springs and exhaust are far above gears on priority. If/when I get it done, I'll let you know how the road manners are. I am prepared to kiss any and all wet traction goodbye with my foot.

Paul - Yes, I am sure that the diff in my friend's Mustang is an 8.8 and that my diff is also an 8.8.
 

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Paul - Yes, I am sure that the diff in my friend's Mustang is an 8.8 and that my diff is also an 8.8.
I purchased a kit from Motive Gear, when I put in my 3.90's

I would pick up another 8.8 center section, Put the gears & TL in.
Then swap sections. I can swap centers in a couple of hours, by my self.

:wavey:
 
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