need driveshaft advice

[Jeffguy11]

Hey, now thats its spring ive been cleanin up the mark and decided i want to get rid of this vibration ive had since i did 4.10s.

I looked on super coupe performance and they offer 2 shafts, a 3.5 and a 4 inch, but claim the 3.5 is no good for 3.73 and 4.10. I had never heard of this- i always thought the 3.5 was the way to go. Will the 4 inch fit without any mods? seems big to me. Anybody with any advice/ insight into this? THanks

 

[kustomizingkid]

Some people say the 3.5 is fine, others say you have to go for the 4. If you do get the 4 you miht have to shim the gas tank down a little bit. It really depends on how fast you want to go, do you driving your Mark like Geno drives his?

 

[Jeffguy11]

It really depends on how fast you want to go, do you driving your Mark like Geno drives his?

I don't really go that fast... if i wanted to go fast i wouldnt have gone 4.10 in the first place hahahaha. I guess id like to go within my 1/4 mile

 

[Rich88LSC]

I have the 4". No gears yet but I plan on doing them.

I think the 3.5" has a lower critical speed and since the driveshaft spins faster with numerically higher gears would reach this speed sooner. I have no idea what rpm this would occur at or how much faster the 4" can safely go. Personally I went with the 4" even though I very rarely drive triple digits or run nitrous you never know what is in the cars future and $100 now is a lot cheap then buying another driveshaft later.

 

[Jeffguy11]

I have the 4". No gears yet but I plan on doing them.

I think the 3.5" has a lower critical speed and since the driveshaft spins faster with numerically higher gears would reach this speed sooner. I have no idea what rpm this would occur at or how much faster the 4" can safely go. Personally I went with the 4" even though I very rarely drive triple digits or run nitrous you never know what is in the cars future and $100 now is a lot cheap then buying another driveshaft later.

im not as concerned about the price as i am the fitment- it just looks kind of tight in there with even the stock shaft and i dont want the thing rubbing around

 

[kustomizingkid]

The only rudding I have ever heard of is on the tank, so you have to shim it down a bit.

 

[Rich88LSC]

It is a tight fit but I have no problems with rubbing. But that some people have. Like kustomizingkid said just shim down the tank if it does.

 

[Blenderhead]

I have a 4" driveshaft in my 393 cougar because I do plan on sustaining triple digit speeds with that car. I had to remove the metal shield that goes between the gas tank and the driveshaft. Also with the 4" shaft, if your trans mount goes bad, it will rub on the bottom of the bottom of the floor right in front of the gas tank, and if this goes unchecked, it could wear a groove into the driveshaft and cause it to break.