3.89's or 4.10's better for 18" wheels?

[jaymac]

I'm going with 18" y2k cobra's on an AOD 88. My question before I get my gears done next weekend is will 3.89's or 4.10's offer an advantage over 3.73's, seeing as a plus-size wheel will apparently slow the car down a bit?
I rarely do highway driving, and when I do, I rarely see over 75 mph, so cruising rpm aren't TOO much of a concern, nor is top end speed for the track. basically, I want to know if either of the ratios will make up for acceleration lost with 18" wheels.
Thanks all,
Jeremy

 

[ECU5.0]

if you get the same tire height as the stock the rim size wont matter. its just the weight that you have to think about. with an aod most people say for for the 4.10s

 

[5spd GT]

Never heard of 389's...you probably mean 390's...

410's would give you a bit better acceleration...but I would keep the 373's...it is a good all around good gear to have...

 

[jaymac]

I'd never heard of 3.89's either, until I read about them in the latest MM&FF in a letter to Bernie, someone mentioned hearing about 3.89's and Ken acknowledged them... so I guess they're real... Either way, I'm pretty sure the tire height will DEFINATELY not be the same, as the stock is 225/60/15, and I'll be using 255/40/18. I could be mistaken, but I'm pretty sure they'll be bigger.
I figured 3.73's were the perfect AOD gear for stock tires, but w/ 18's, I 'm wondering if 4.10's wouldn't make up for the bit of pickup I'm losing from increased diameter...

 

[ECU5.0]

theres a formula for determining the tire height...im not sure what it is...but the 255 is gonna be wider...i dont know how much taller it will be though

http://www.novak-adapt.com/knowledge/gearing.htm that site has a tire conversion thing in it. the 255-40-r18 will only be 0.4 inches taller than the 225-60-r15. so i dont think you have anything to worry about

 

[jaymac]

oh wow, very good info, thanks alot...so now...3.73's or 4.10's??? hmmmm...
keep in mind engine is stock....

 

[85_SS_302_Coupe]

AOD-Get the 4.10s.

5 speed-GET THE 4.10s!


It's like they said above, if you have a stock sized diameter rim/tire package, it doesnt matter what your rim size is if it equals out as the same as a stock package then you'll get the typical results of each gear.

So lets say your 18s end up being a little taller than the typical stock size combo. This means that you're actually going to feel a slight LOSS in gear, because the larger tires require more distance to make one complete revolution, which sort of evens out the gear ration. If you ended up with a smaller than stock size combo, such as a 15/R50 setup like i have, then you'll feel a GAIN in gear, which is why my 4.10s almost feel like a 4.30.

If you had 3.90s and a short tire, it would feel more like a 4.10
If you had 3.73s and a tall tire, it would feel more like a 3.55


Make sense? I say get the taller tires/rims to fill those wheel wells, then get the 4.10s.

 

[jaymac]

Cool, makes sense..so 4.10' s it is... now, a question for you 88 : I see you have the a/c delete kit and short belt? i was about to order an a/c delete from UPR today. Now, with your delete kit, is there still a pulley there? or no? If so, what size belt are you running and did you eliminate any other accessories? Thanks,
jeremy

 

[jaymac]

a member posted that he just pulled the unit and bracket and tensioner and put a 77.5" belt... anybody else had exp. w/ this?