zr1clone

I was wanting to swap out my gears from the (airplane) 2.59 to maybe a 3.73 or 4.10. I have seen many write-ups and info here and found some info on speed gained. I have read that for every 0.2 (2 tenths) in gear change you can expect to gain 0.1 (tenth) of a second in your 1/4 mile time. Does this seem right? I also wanted to know if anyone could explain the top speed loss from a gear swap like this. I don't want to go 150 mph but 120 would be fine as a top speed. as long as I can get there fast. I have the Dana 36 rear end and 700r4 transmission. My 1990 is stock except for the exhaust which is 2.5" no cats, no x-pipe and dynomax turbo mufflers. Thanks for the replies.
--ZR1clone

TA

Without engine mods a L98 doesn't need a lot of gear. It seems to be the consensus around here that 3.07 is pretty much the optimum gear for an auto L98. If you go to a 3.73 or a 4.11 I can almost guarantee your car will go slower in the 1/4. The L98 has a torquey, low RPM power band and a steep gear will get you out of that power band too quickly.

I've had 2.59s, 3.07s and a 3.33 in my bolt-on L98 and the 3.07 was definitely the best all-around for the 1/4. My current 3.33, probably gets me out of the hole quickest, but I lost a bit on the other end.

I'd go 3.07, a 2500 stall TC and sticky tires and you'll be maximizing a L98 stock set-up.

See my sig for my set-up.

zr1clone

thanks for the quick reply. I don't want to start drag racing. The seat of the pants feel is what I am after. what will the 3.07 turn my shift points to?

Jared1984

I 100% agree. I had an 89 W/a mild cam, 3K stall and full bolt ons. I swapped in a dana44 that had 4.10's (from a 6 speed car) and The car was a BEAST down low That car went 1.62 60' and 12.5 1/4mile. However, that's where the pro's ended. Cons-To me...it was too much gear for an auto. Highway driving sucked. Anything over 55mph wasn't enjoyable B/C I was at close to 3K rpm. Top end really got chopped, top speed was around 115 or so. Plus gas mileage really suffered. Not that top speed or gas mileage really mattered that much to me but....

Anyways, for you set-up, I agree with TA. If you had a ton of mods and did 90% drag racing, then I'd say get the steeper gear. To go too much, you'll deff regret it

xrcrx

I've got 375's and at 70 its around 2400rpm. Its a rocket outta the corners and a lot of fun.

zr1clone

Z51 that is good to know... since I found D36 "pumpkin" w/ 3.73. I was thinking that I could swap the two carriers and sell my old 2.59. I was tolf that I would save time and money this way. The owner of the 3.73 rear pumpkin is swapping to a D44... he's pushing 450 hp.

rodj

Facts.
3.73 / 4.11 are drag racing gears unless you have a engine that revs.
L98's don't rev....(it might show 5500 on the tacho but you are out of power at 4500)
If you hit it hardoff the line ,traction is marginal with 3.07-L98 combo due to great L98 bottom end unless you have DR's.
As stated by others ,for L98 especially stock ;
3.07 is best combo of SOTP , performance and economy
Your SOTP feel will be you sitting still while your tires go up in smoke with 3.73's

zr1clone

Thanks for making it plain and simple to understand, Rodj. Anywhere you can recomend to get 3.07s? Or the whole carrier?

RedDwarf

see I wonder how that can be..my bone stock '90 auto is running just shy of 3000 rpm at 70???

pologreen1

if it is an auto you might want to check your tv cable or something, it might not be going in to overdrive or is that in d