3.73 or 4.10's ?

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StraDog

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I have decided that changing the gears is a must on this car. I just drove in "MarkofDeath"'s nice 94 Mark with 4.10's and I absolutely love it. The thing is I would rather not want to cough up another $500 for a new driveshaft. I have been thinking of going for the 3.73's and perhaps putting that extra $500 straight towards a 125 shot. I'm not a "heavy" racer, so the 4.10's aren't that big of a neccessity. Anyone have any input on 3.73's and how they perform. I just want a bigger gear, but don't want to spend that extra money on a driveshaft.

Also, when purchasing the 3.73 gears, installation kit, and posi center piece, what else would need to be bought ? Fill me in on some info. ( I really don't want to spend that money on a new driveshaft ;( ) :feed

Thank you very much for your time.
 
Flip a coin, you cannot go wrong with either ratio.

The easiest and most cost effective is to buy the Motorsport Cobra center section with 3.73's and do a pumpkin swap, driveshaft and speedo correction unit and your done.

If you do it component for component then you will see a higher bill $$$ in parts and labor.

The pumpkin swap is about a 2 hour job too, much faster and easier then setting up the gears and what not.
 
I understand your plight Jon. 3.73s or 4.10s... 3.73s or 4.10s... 3.73s or 4.10s... deja vue. ;)

The answer for me was 4.10s. Then next came the driveshaft issue. Ask Brad to tell you what I went through. I ended up with the MMx driveshaft simply to save time and hassle and get back to enjoying my car.

Regardless, there are those who stayed with the stock driveshaft(even the 2-piece) and went with 3.73s with no vibration issues(at least at highway speeds). Then there are those who replaced their 2-piece shaft with a 1-piece shaft when they went to 3.73s or 4.10s.. Those that went 3.73s seemed to fare better than those who went 4.10s as far as vibration issues are concerned.

You should be able to do a search for all that's required in the changeover. If you can't find it, I can fill you in later. :L
 
Thanks much for the input guys. So if I do decide to go with the 3.73's, I can stick with the stock driveshaft ? I have heard some who stayed and had no problems with vibrations much like what you said, driller. I just need a little bit more knowledge on what needs to be bought and then hopefully can find a shop to do it for a good price.

I'll search around a bit. I think 3.73's are the final decision. Alittle more input is all I need. :Bang
 
Unless you are loyal to a shop. Search around for the best price! I had mine done by the shop I always go to. That way if they do something wrong I know they will fix it. Also, my guy said to bring it in after 500mi for a free check up and if anything needed to be replaced due to his mistakes. Free Replacement! So, ask the right questions.
 
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Sifrino3 said:
Unless you are loyal to a shop. Search around for the best price! I had mine done by the shop I always go to. That way if they do something wrong I know they will fix it. Also, my guy said to bring it in after 500mi for a free check up and if anything needed to be replaced due to his mistakes. Free Replacement! So, ask the right questions.
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Yea thanks for the advise. I'm pretty loyal to a couple shops. I will definently search around though. 500 mile check up, thats awesome service ! :Beer

Thanks again.
 
Start with the 3:73's. You will never know with the driveshaft unless you run it OR does your car vibrate at 90 mph now. Because that will be approximately the same revolutions the shaft will see at 70 mph with the new gears. That's the best way to find out. Also, you can always pull the 3:73's and swap in the 4:10's later if you want. I think there is a decent market for the 3:73 so you should be able to sell them if you choose the upgrade path.
 
MonsterMark said:
...You will never know with the driveshaft unless you run it OR does your car vibrate at 90 mph now. Because that will be approximately the same revolutions the shaft will see at 70 mph with the new gears...
Click to expand...

:F

I beg to differ here. Just because you have no vibrations at the equivalent driveshaft rpm now is not a guarantee you will not after the gear change. A lot comes into the mix that determines driveshaft NVH issues. However, I will concur your chances of having no vibes at 70 MPH with 3.73s is pretty much zilch if you have vibes now at 90 MPH with stock gears.

If you go with 3.73s, I would purchase the FMS Cobra assembly and be done with it. Then sell your stock center section to recoup some spilled beans. I agree with MonsterMark when he says if you change your mind and go with 4.10s later, the 3.73 assembly is an easy sell. You can easily swap out the center section in an afternoon with a helper and no lift.

If you elect to build your own, the real fun begins. That's a whole topic of itself. ;)

If you just buy the parts and have a reputable shop do it, here's what you need:

PART NUMBER DESC
M-4209-G410 Ring & Pinion
M-4210-B Installation Kit
M19546A Friction Modifier
M-4204-F288 Traction-Lok differential

Also you will need 2 axle bearings and 2 seals for the outputs of the center section and 2 axle nuts. And don't forget the correct speedo gear along with gear oil of your choice. Now is also the time to replace those carrier bushings.

Check with the shop you plan to use as they may be able to get better pricing than you as an individual. Some shops will not even install customer supplied parts.
 
MonsterMark said:
Start with the 3:73's. You will never know with the driveshaft unless you run it OR does your car vibrate at 90 mph now. Because that will be approximately the same revolutions the shaft will see at 70 mph with the new gears. That's the best way to find out. Also, you can always pull the 3:73's and swap in the 4:10's later if you want. I think there is a decent market for the 3:73 so you should be able to sell them if you choose the upgrade path.
Click to expand...

Sounds like a plan..... Good advise.
I'm actually going to see how it feels driving at 90 mph on the way to work. That should seem to be what it feels like going 70mph with the 3.73 gear then, correct ?
 
I don't think going 90mph will be what 70mph with 3.73 are. I have 3.73 in my M7 and I will get vibrations in the MPH I can't see. Right before I top out on my rpm. It will start vibrating. This is above 120mph. I don't have any other problems with vibrations just going through the gears. But this is a M7 not an M8! So, im sure there is differences.
 
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I appreciate the comments but we are talking about the Mark VIII which has a wide history of problems with the harmonic balancing on the driveshafts. Some will vibrate with stock gears, others won't even vibrate with the 4:10's or even 4:30's. It is a hit and miss type of thing.

Ya Stra Dog, run it up to 90, take a look in the rear view mirror and if it looks like your on the D.T.'s, I would expect the same vibrations at lower speeds with the new gears.

The worst is if your vibration occurs at a very popular speed. In my case, the '98 vibrates between 70 and 85. I do alot of highway so it is very unpleasant. I am swapping shafts out of one of the '93's. I know the '93 is butter smooth up to 140, so that should take care of my problem. You can always look in the bone yards for a 93 with the one piece shaft. I wouldn't let on that they have any value so you should be able to get one for under $100.

Good Luck Dog.
 
Sifrino3 said:
Can't you just get it re balanced? If it has problems. Thats what I would do before I do anything major.
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I heard you can't balance a two peice shaft, The reason why the shaft vibrates is because it is not rigid and flexs at high speeds, but Jon what if you get 3:73s and your drive shaft vibrates, then you end up in the same spot as 4:10 just a couple tenths slower. The driving up to 90 thing does not work I drove up to 118 before my gears and it didnt vibrate. So the choice is yours.
 
Well I took it for a ride today and found that there is barely any vibrations at 90 mph. Last night on the way home I was doing 115 and found some vibrations. So I might just go with the 3.73's and leave the stock driveshaft in for now. If I do need to change the driveshaft later, I will. :Bang

End of story. :)

Thanks for the replys.
 
Ya you might need a new Drive shaft because of the vibs at 115, so that vib will come in at 85 to 95 now
 
StraDog said:
Thanks much for the input guys. So if I do decide to go with the 3.73's, I can stick with the stock driveshaft ? I have heard some who stayed and had no problems with vibrations much like what you said, driller. I just need a little bit more knowledge on what needs to be bought and then hopefully can find a shop to do it for a good price.

I'll search around a bit. I think 3.73's are the final decision. Alittle more input is all I need. :Bang
Click to expand...

Hi I bought a 3.73 rear end from max for my 93; I bought the car up to 100, still very smooth now I have the stock one piece drive shaft, i think only 93 has the one piece shaft.

Rick
 
Hey guys,i just read through all this thread and was wondering how much difference you guys felt with 3.73/4.10 compared to stock 3.07/3.27 ,
also how was fuel econ changed city/hwy?

while we are kinda on the subject.....
my dad thinks his 93 with 3.07's is quicker than his 98 lsc with 3.27's
why are gen 1's feeling stronger with less gear and 10 less horsepuppies?


Mike
 
Moes8 said:
while we are kinda on the subject.....
my dad thinks his 93 with 3.07's is quicker than his 98 lsc with 3.27's
why are gen 1's feeling stronger with less gear and 10 less horsepuppies?


Mike
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There is no difference in horsepuppies between the 93-96 vs. the 97-98, UNLESS one is the LSC model. If either are a LSC model it will have 290HP, whereas the non-LSC models are only 280. Oh, and usually only the LSC have the 3.27 rear ratio.

Also, it seems to be a general consensous that the 97-98's are slower than the 93-96's......not sure if anyone really knows why......
 
Geno, what exactly do you need to do for just a cobra pumpkin swap?, i see em used all the time.....let me know, thats what i want to do :Beer
 
1wykdmk8 said:
Also, it seems to be a general consensous that the 97-98's are slower than the 93-96's......not sure if anyone really knows why......
Click to expand...
The intake breathes better in the upper rpms in Gen 1 and the computer has a more aggressive flash as far as the timing goes and I'm not sure on the A/F, but I suspect it is leaner.
 
If this is true, why was the HP rating unchanged from 93-98?


MonsterMark said:
The intake breathes better in the upper rpms in Gen 1 and the computer has a more aggressive flash as far as the timing goes and I'm not sure on the A/F, but I suspect it is leaner.
Click to expand...
 
MonsterMark said:
The intake breathes better in the upper rpms in Gen 1 and the computer has a more aggressive flash as far as the timing goes and I'm not sure on the A/F, but I suspect it is leaner.
Click to expand...


Am i correct in saying that Lincoln removed the low/hi rpm butterflies for 97-98(gen2)?
I think i remember reading that they reworked the intake manifold to work well without the butterflies,

If that is true then,my near worthless theory was that maybe "peak" hp was the same,but maybe hp over the rev range was not as consistently strong.ie gen 1 have "wider" powerband.....???!!!...
i have no idea if my thoughts are even closely accurate.
Anyone????

Mike
 
what do i need besides the cobra pumpkin for a swap, geno said sumthin bout a driveshaft and speedo calibraton, can i use the stock d/s?,i'm gonna ebay and salvage yard the parts for swap,as they say...." one mans trash is another mans treasure!"
 
The only reasoning I have is that L/M understated the performance. What we need are a couple of dyno reading from a stock '93 and compare that with a stock 2nd Gen.

If we do enough digging, we may be able to come up with both. That may reveal the answer.

brentalan said:
If this is true, why was the HP rating unchanged from 93-98?
Click to expand...
 
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