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post #1 of (permalink) Old 10-22-1999, 09:29 PM
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diff gear ratio\'s

I just dissasembled my rear diff because I'm changing the gears. I was told that this would be difficult but so far it's been a piece of cake.

My question is I have an 8.8 rear and everyone assumes that the stock gear ratio is 3.55, even when I bought the new gears the guy at 4Wheel Parts Wholesalers assumed that I had 3.55's. I bought 4.56 gears because I run 35x12.5 BFG's and plan to get 39" Super Swampers next. Do you think having stock 3.08's will make a difference or is this a moot point.

As always any response is appreciated.

Alex.

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post #2 of (permalink) Old 10-23-1999, 01:11 PM
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Re: diff gear ratio\'s

stock 3.08s? and 39s? whoa thats not a very good combo. You will have very little power, and it will decrease the life of your engine a little. What type of engine do you have? The wheels WILL turn, just not very good.

Roland

post #3 of (permalink) Old 10-23-1999, 07:53 PM
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Re: diff gear ratio\'s

>>>The only difference going from 3.08, instead of 3.55, to a 4.56 ratio is that your speedometer will be a little further off. You will read about 72 miles an hour when your going an actual 65(35s). 3.55s to 4.56 would have left you almost exact with 35s. The 39s may make the actual speed a little closer to the speedometer. You may be able to change the gear that goes in the tranny to accomodate any difference in speed. You'll have to check with Ford to find out for sure though. I had 3.55s and put in 4.56s with 36 inch tires and the speedometer was within 1 mile an hour at 65 so I left it alone. I was fortunate enough to have a friend with a GPS and he was able to check our actual landspeed from inside the truck and compare it too my speedometer. By the way, do you have a 5.0 or 5.8? The reason I ask is due to the weight of a Swamper compared to anything 35x12.5 that is radial. If you have the 5.0 you may want to stop at 36 inches unless you are going to do some perf mods to the motor. If you have a local 4x shop with display tires go on in and lift a few and you will see what I mean. If, when I put my 36 inch Swampers on, I had known they would weigh so much more than my buddies 35x12.5 BFGs I would have went one gear deeper to accomodate the rolling weight resistance they have. P.S. Don't forget harder to move means harder to stop-might want to look into a rear disk set up for all that rubber. I'm done now. Later.

NUFF SAID
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post #4 of (permalink) Old 10-24-1999, 12:56 AM
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Re: diff gear ratio\'s

I have the 351W in my truck. With the 3.08 gears and the 35x12.5 tires my speedo was off by 20%. The only mods I have done are an MSD ignition, K&N Filtercharger Kit, Jet Performance Module and JBA headers with a Flowmaster 50 Series muffler.

Just an update on my gears. I'm doing the rear first and I have everything set up. Right now I'm working on the backlash adjustment. I grinded the insides of the old pinion gear to make the setup quicker. So far it's been cake. I'll keep you posted.

Alex

post #5 of (permalink) Old 10-24-1999, 10:25 AM
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Re: diff gear ratio\'s

Ford Broncos with 8.8" rears came with 3.08, 3.55, and 4.11 gear ratios. Mine came with 3.08 gears and IO just
swapped in a ford 9" with 3.50's to help turn my Q78's9(skinny 36's) I plan on ordering. I was running 35" AT's with
only the 3.08 gears and loved it, but then again the good old 300' sixer loves the low RPM's. I'm running enough
power with the built-six to put a stock 5.8L to shame.

Do'n it with only 6 cylinders!
post #6 of (permalink) Old 10-24-1999, 11:33 PM
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Re: diff gear ratio\'s

Which mods have you made to your 6 I'd like to hear about them. I always thought that smaller engines liked higher rpm's. But then again your six is almost the same size (displacement) as the 5.0.

Alex.

post #7 of (permalink) Old 10-25-1999, 11:31 PM
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Re: diff gear ratio\'s

the list is long, but for the percentage of power gain, the price isn't bad....... The 300-6 from the factory has
more torque than a 5.0. a 302 has a bore of 4" and a stroke of 3" and a 300-6 has a "square bore" 4" bore with
a 4" stroke. Square bore engines make great bottom end power and decent HP but don't rev RPM's very good.
the difference in cubic inches is only .5" in factory form. My 300-6 is bored .030 over (306 in^3) with the block
shaved down so the pistons are level with the deck (9.2:1 comp. ratio). I gasket matched the head to the
Offenhauser 4bbl intake and mounted a holley 450cfm carb on it. I then have the exaust exit out a set of Hooker
headers which each flow thru 2" pipe for 3' the y together into a 3" in/out bigblock series flowmaster muffler and out the side
in the factory position. thew single pipe out makes more power and is quiter than the true duals I used to have.
For a bump stick I have a CompCams 260H cam along with lifters and valve springs. I still have to get a
new distributor but I can walk all over my dads stock 85 351W h.o. bronco on and off road, while getting better mileage
I would have gone to a 429 but that cost too much money at the time and I really love my torqy little 6 popper now.

Do'n it with only 6 cylinders!
post #8 of (permalink) Old 10-25-1999, 11:43 PM
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Re: diff gear ratio\'s

sounds like the price for the mods is pretty steep unless you did the work yourself.

post #9 of (permalink) Old 10-26-1999, 07:18 PM
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Re: diff gear ratio\'s

I cost me about 150$ for machining(.030 over bore, head shave, block shave) About 500$ for the complete
kit including new comp cam, lifters and, valve springs. About 400$ for intake/carb combo and 200$ for headers
and exaust. I spent about 1350$ when all was said and done, but I have a like new engine that huals a$$ for 6 popper
Just to put the Junk yard 429 in my bronco would have cost 1000-1500$ plus the cost of a rebuild kit and speed
parts......

Do'n it with only 6 cylinders!
post #10 of (permalink) Old 10-26-1999, 08:45 PM
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Re: diff gear ratio\'s

You're absolutly right in your decision in sticking with the old engine. I had a Buick LeSabre and it was a great car. I snaped the crankshaft and instead of keeping the engine I had which I knew was solid, I went with and engine from a junked car. The replacement engine lasted about 6 months. I guess you learn from your mistakes.

Later,
Alex

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