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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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It seems to vary, but yes. Between 105 and 112 is usually where it kicks in. The speed limiter is mostly to protect the drive shaft.
 

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It seems to vary, but yes. Between 105 and 112 is usually where it kicks in. The speed limiter is mostly to protect the drive shaft.
Not exactly. :rolleyes:

Well ... the speed limiter is to protect the DRIVER, any passengers and the general public from driveshaft failure in addition to the speed rating limitations of the stock tires. The last thing you want is for a driveshaft or tire to fail at those speeds.

There are numerous mechanical and safety reasons for the speed limiter.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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The question to ask is why do you need to go that fast? Do you take the car to the strip? Have you upgraded anything?
 

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The speed limiter has absolutely nothing to do with the driveshaft. If the driveshaft fails from high speed, what happens is the crimp joint becomes loose and slips, which mis-aligns the u joints and it causes a bad vibration similar to what a bad u-joint feels like, but it will not fail in such a way that it would cause an accident. It has never happened, and never will, but for some reason this myth has been propagated on this forum since day one. The reason the speed limiter is there is due to the tires, and only the tires. The factory installed S rated tires are only rated to 112mph, so a 105-109mph speed limiter will help insure that you don't overheat the tire and cause a blow out at high speed. That is why the SCs, which have the exact same driveshaft but have H rated tires, which can withstand 130mph, don't have that speed limiter.
 

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I can attest that some (at least one) 5.0 cars don't have them.
 

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I ran the stock driveshaft on my car for years with the supercharger,3500 stall and 3.73's. Many runs well into the triple digits not to mention countless launches and track time. Never broke. Just vibrated after 80mph.

I believe the fastest I went on a stock shaft was 120ish mph. That with 3.73 gears over the stock 3.27s was more like 130-135 for the driveshaft. <---thats just a guess seeing after the gears it topped out at 92mph before my tune.
 

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I spun a stock driveshaft inside itself. Stock engine, locker rear, entrance ramp in second. I thought it was the clutch shell, lol. Highway driving kills them quick.

I also had another car's DS do the wobble thing mentioned above, and it caused the tranny rear seal to die, the diff to wear really quick, and a strange wear pattern on the rear wheel bearings.

Before driving at high speeds, I'd make sure you have good shocks, the DS is upgraded, the front and rear uca and lca bushings are in good shape (Hell, the whole front suspension), as well as good tires.
 

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MarkVIII driveshaft won't work because it is a different length. If you want to upgrade your driveshaft to an aluminum one, it will have to be aftermarket as there is no factory installed aluminum driveshaft that is the correct length. However the only real reason to upgrade the driveshaft is if you are getting vibration issues with your stock one.
 

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not all cars have speed limiters from the factory. the car i had before i got my bird this past monday didnt. 93 taurus sho. says it tops out somewhere around 143mph. after 138ish i backed off, close enough.
 

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I forget the pcm code but there are 93 marks without speed limiters.
 

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Can't you bypass a limiter?
Lonnie said:
Bypassing the speed limiter
You need to place a mini switch inline of the Vehicle Speed Sensor VVS signal to the Electronic Engine Control EEC. This wire is identified by the connector going into the EEC. Look for the numbers at the one end of the plug 41 21 1. The wire you want is #3. So start at wire 1 and count to 3. The color of the wire should be dark green with a white stripe. Do not just cut the wire and leave it. This signal also controls your Idle Speed Control Solenoid ISC or the air bypass valve, while the car is at a stop at idle or the A/C is on. So it could cause you to stall if in the bypass mode while at a light or stop.

This method only works on 91-93 5.0 Thunderbird and Cougar's



Rayo...
 
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