pennywise

will this rear end be suitable for a daily driver? I know the 4.77 would be way to short, and would be cruisn at a high rpm.

peejay

I did the math for a 4.778 gear, as compared to a 3.909 gear. ('85 GSL)

The difference between the two is 1.222. 1.222 times the .825 stock 5th gear is 1.008. So, basically, with 4.77 gears, 5th gear would be where 4th is now.

This is fine by me, as I consider 5th to be too tall anyway. If I use 5th, I have to downshift a lot on the highway to keep the engine happy (I do NOT lug my engines) and more often than not I just leave it in 4th gear. So, by switching to the 4.778 gears, I'd be able to use all five gears.

Considerations for city driving are a moot point. I typically only use 1st through 3rd in the city. There are more gears available, in other words.

the_glass_man

iTrader: (2)

4.3 and 4.7 are fine for daily drivers, why wouldn't they be? You need to go over 180 mph a lot?

pennywise

no, I don't even want to go over 150. I just didn't know if having your rpms high all the time would put a strain on the engine or turbos. would the 4.77 give me a lower et than the 4.3? I plan on geting to4e or something no bigger than an .80 A/R. so with that in mind I wanted a gearing that would corrispond with a somewhat smaller turbo.

peejay

Keeping the RPMs higher makes life EASIER on the engine. It's under less load that way.

The turbo is under no "load" when it's not producing boost. Turbo speed is mostly a fuction of boost, not engine speed.

pennywise

thanks peejay i didn't know that. so what do you think would be ideal for drag racing, the 4.33 or the 4.77 what would give me a lower et

peejay

Probably the 4.77.

fastrotaries

If you're going to run a 4.77 and athen give it boost or NOS. you'll go through first real quick. How quick is directly proportional to power and traction. 4.33 should be good. 4.77 might be a little too much. This just all depends. For anything other than drag racing though, this wouldn't really come into play.

mkoch1

I have 4.777 and at the strip if you blink you hit the red line in first. I was told you could lower your times by .25-.5 seconds. It does make 5th pull like 4th used to.

peejay

Lighter flywheel would be a good complement to a 4.77.

Related to this subject, I had an old Subaru (Oh god, here we go again... ) with a dual-range transfer case. In Low range (1.89 or so multiplication in addition to the 3.909 gearing) the car would actually pull harder in 2nd than in 1st gear. As you go deeper in your gearing, your acceleration gains get less and less as your ability to accelerate in 1st gear asymptotically gets to the engine's ability to rev to redline with no load at all. The Suby had an enormously heavy flywheel (30lb? Something absurd) and it would take about 3 seconds to hit redline if you floored it in Neutral. In 1st gear and Low range (what is 1.89 times 3.909, something like 7:1 effective rear gear?) the engine was mostly accelerating ITSELF.

So, basically, the lower your gearing, the more you need/benefit from a lightweight rotating assembly, since the engine has to accelerate itself much quicker in 1st gear.

If you don't care about 1st gear, then there's really no point to a lower rearend gear, since that's pretty much the only gain you'll have.

93redFD

the 4.777 will kill your gas milage.. 4.33 is were its at..
If your strickly drag racing I would not recomend a light weight fly wheel.. I had a pettit 8.5 and could not stay in boost when shifting gears, on top of that , if you get in the stop n go 5 oclock traffic, have fun with the street/strip clutch and lw flywheel.