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Gears

Posted: Wed Jul 29, 2015 6:50 am
by Jim100
My 1970 W-100 has 4.10 gears. I have been driving it a lot more recently and further distance. I am nearing the end of my patience with the low gears and have 33 x 9.5 tires already. Has a freshish 360 four barrel so plenty of power, I dont pull trailers or haul super heavy loads.
What is the tallest gear set that is not a total highway gear? And is changing gears in my Dana 44 front possible? The rear 8.75 I can handle.
Thanks all
jim

Re: Gears

Posted: Wed Jul 29, 2015 12:29 pm
by JimBobTheDancingBear
3.23's seem popular as do 3.55's.

What about switching to a 5 speed tranny and keeping your gears?

Re: Gears

Posted: Wed Jul 29, 2015 9:33 pm
by powerwagon54
5 speed trans is not going to change anything. 5th gear is direct and so the high speed stays the same. Unless you can find an overdrive.

Re: Gears

Posted: Fri Jul 31, 2015 11:31 am
by spesce
Spicer brownie box

Re: Gears

Posted: Sun Aug 16, 2015 9:37 am
by WD
3.73 is about as high as I would consider. You can run a 3.54/55, but a 33" tire is right at the limits for that high of a gear.

I have worn out LT285/75R16D ATs on my 4wd right now, 330hp at the crank, 2 speed automatic and locker equipped 4.10s. Top speed is 60 mph (would peg the needle before 3rd and 4th failed).
I have worn out LT235/75R15D ATs on my Swept. 210hp at the crank, 3 speed auto and open 3.55s. Top speed is 60 mph, downhill, with a strong tail wind and the throttle to the frame rail.
I have barely worn 6.00-16 4 ply street rib bias on my Pilot House. 90hp at the crank (218 flattie), 3 spd top loader and open 4.78s. Top speed (new) was 54 mph.

Call Yukon Gear or similar and tell them what you are running. Engine, transmission, t-case, what axles with what gearing, tire size-load rating-tread, and primary usage of the truck. Let their calculator do the work optimizing what ratio you actually need.

Re: Gears

Posted: Sun Aug 16, 2015 8:11 pm
by marklein
What is the rpm at 60 mph? In theory it should only be running at 2500 rpm as it is. It would run about 2000 rpm at 60 with 3.23's, 2200 with 3.55's. 33's turn about 611 revolutions per mile, so use that number times the diff ratio to get theoretical rpm. It gives a general idea, but isn't 100 % correct, too many other variables. I would say that 3.55 would be the minimum, 3.73's are available, but not much under what you have at about 2300. Then figure out how much gas you can buy for what it will cost to change gears. Got room for 35's?

Re: Gears

Posted: Mon Aug 17, 2015 2:36 pm
by Hobcobble
3.55 :2cents
John

Re: Gears

Posted: Tue Aug 18, 2015 11:05 am
by Jim100
Cool thanks guys.
jim

Re: Gears

Posted: Sat Oct 10, 2015 10:28 am
by swptln
What is your top speed?
I have 4.88's with 34's on my 68 W200 and she will run 65-70 with no problem, it's wound up pretty tight around 80-90, but it will go. She likes fuel though at highway speeds, I run 55-65 most of the time on the highway. If I want to pull out and pass, it goes with no hesitation. I've towed cars from MA to PA running 60-65 a number of times, hauled my slide in camper to VT, PA, NY with no problems driving on the highways. I was probably only getting 7-8 MPG which is expected towing vs 10 MPG off the highway empty.
If you can't get 80 mph out of a 360 with 4.10's and 33's you have something seriously wrong.

Stock 318, 2.5" dual exhaust, Walker mufflers, iron manifolds, iron intake, carter 2bbl, MP Electronic ignition, wide ratio NP435D3, 16" wheels w/LTB 34x10.50 super swampers.

http://www.sweptline.org/SweptlineRegis ... 2281820618

Re: Gears

Posted: Mon Nov 23, 2015 10:36 am
by Jim100
80? Im sure it will do it and more its just reving high at that point and I wouldnt want to hold it there!
Is the 3.23 ratio made for automatics?

Re: Gears

Posted: Mon Nov 23, 2015 11:23 am
by Hobcobble
Jim100 wrote: Is the 3.23 ratio made for automatics?
It'll work in either. :2cents
John

Re: Gears

Posted: Mon Nov 23, 2015 3:34 pm
by Jim100
I just wondered if there is somthing about an auto that uses a higher ratio better? Does that make sence? Will my np 435 be crippled by a 3.23 where a auto would not?
Thanks.

Re: Gears

Posted: Tue Nov 24, 2015 6:54 am
by swptln
Jim, it doesn't make much difference, 4th gear in a 435 is 1:1 ratio as is 3rd gear in a 727. So, your rpms will be the same, your shift points are the only difference.
As mentioned I wouldn't drop your ratio to 3.23's with 33" tires, it will be gutless on the bottom end.
Personally, the lowest I would go is 3:91's with 33's, but I love my 4.88's and 34's combo.

Don't be scared let her rev a little :lol: :Thumbsup