time benefit from 3.07 - 3.45?

[rrubel]

I'm picking up a 3.45 ring and pinion from an LT4 for what I think is a decent price ($85, shipped, has 28k miles on it).

Since they're both Dana 44's, it should be a fairly easy swap, right?

Anyone tell me about what sort of gain I should see in the 1/4 mi? I realize it's not a radical change, but I still do a lot of highway driving and 4.11 would be a bit much . My gearset also has 140k miles on it and is probably getting a bit worn.

[RICHR]

 

[vader86]

0 gain in the 1/4mi, youll probably lose some ET with the L98 unless you have changed the intake

although you will gain in 0-60 times

 

[rrubel]

The project that includes the gears also includes a SuperRam, new cam, head work, manifold, the works.

Out of curiosity, why would I gain in 0-60 but not at all in the 1/4 mi?

[RICHR]

 

[vader86]

If its SR and 219, still 0, but you wont lose anything in the 1/4mi. Ive seen track results to prove that.

Its because the powerband in the L98 is so short, it only makes good power at low rpms and the 3.45s will get you to high rpms quicker than the 3.07 gearing. So youll spend more time at higher rpms than at low rpm. 0-60 you would get to your peak rpm power faster and would accelerate great up to that point, but afterwards you really fall on your face.

 

[rrubel]

So it would be good, then, for something like autocrossing where I'm on and off the power a lot.
[RICHR]

 

[MagikDraggin]

So it would be good, then, for something like autocrossing where I'm on and off the power a lot.
[RICHR]

From that perspective, yes. Those short little power-sprints in autocross would definitely benefit from the lower (numerical) gears.

 

[kingman]

Gear change!!!!!!!!!

Hi

What you are telling me is that my 3.07, so called performance rear of my 96 LT1 would not really benefit from changing to a 3.73 rear.

As far as gas mileage, it doesn't matter to me what l lose.

It was my understanding that the cheapest and best performance
thing was change the gears.

Best bang for the buck!!

Alan

 

[rrubel]

You've got an auto transmission, right? Different engine, different story - the LT1 makes its power higher, so the higher gearing (IIRC, normal auto is 2.59?) helps you more than it would me. I think I've got that right.
[RICHR]

 

[kingman]

Gears

Hi

You are correct it is an automatic. l thought that the best way to enhance my performance is a gear change.

But would going from a 3.07 to a 3.73 be worth it?

Most of my driving is under 70mph because l'm not looking for a ticket. What l am looking for is 0-60 performance and maybe 0-100 when conditions allows it.

Do l have to change only the ring and pinion or is there more?

Also, should l keep the 3.07 gears in my garage?

Thanks

Alan

 

[vader86]

For the LT1, its the reverse argument. It makes its power at midrange and high rpms, so you would benefit from the gearing getting you to high rpms quicker. You would gain alot in the 1/4mi from adding gears to an automatic or stick LT1. 0-60 would be quicker too.
Then if you added a 2400-2600 stall TC, you could be in the 12s.

If you already have 3.07s in the automatic, you can just change the ring & pinion as long as its for a Dana 36. I would keep the 3.07s unless i'm hard up financially.

 

[MagikDraggin]

Re: Gear change!!!!!!!!!

Hi

What you are telling me is that my 3.07, so called performance rear of my 96 LT1 would not really benefit from changing to a 3.73 rear.

As far as gas mileage, it doesn't matter to me what l lose.

It was my understanding that the cheapest and best performance
thing was change the gears.

Best bang for the buck!!

Alan

If you are referring to my post, I erred in saying "numerical lower", when I meant numerical higher.....

Sorry 'bout that. Yes, 3.73's would make your LT1 "cook" compared to the 3.07's.

 

[invinceablevett]

Hi there,I have changed my Differential gearing to 3.73 in my 92 automatic convertible.I had a little trouble getting used to the higher rev's on the highway but I love them now.I like the quick response when driving in the city.This is not my daily driver so gas wise I don't feel the pinch in my wallet.I ran a 13.60 1/4 mile l2 years ago,(although I think I can do better with some of my minor mods.....Fuel pressure regulator,forced-air induction,k/n filter,power pulleys...........I can't tell you how much I was running the 1/4 before the mods because I never tested it then.I am curious to know how much faster I am as opposed to stock.

 

[kingman]

Ring & Pinion?

Hi Vader

I will keep the orig 3.07, but can you give me an idea on an approx price on how much it should cost to have the 3.73 put in.

All l need is an approx amount for the ring & pinion installed by a real shop and not a corner service station. l'm not trying to save a dollar, just want it done right.

I saw some ads that offer changing the gears installed for $1300 for the differential (whole package)

Also, what is this 2400-2600 stall TC???????????

Thanks

Alan

 

[vader86]

TC is Torque Converter in the transmission (kind of a clutch for an auto), it does almost the same thing as the gears, except at launch.
When you step on it now, your engine revs up to say 1500rpm before the TC locks and all the power of the engine is transmitted thru the driveline. A higher stall TC would wait until 2400-2600rpm, rpm stall depending on your choice and ET goal, before locking.

This would greatly reduce your 60' times at the track, and together with gears and practice, will have you knocking on the 12sec range.

Whereas a normal LT1 auto should get mid/upper 13s, the gears and TC take .5-.7 off the times by just putting the power to the ground better.

The best brand of TC is probably PI Vigilante, but its expensive. Yank makes a good one too.

dont recall for sure on prices though

 

[kingman]

Hi Vader

Would it make sense to do the rear end then the torque converter???

You noted 2400-2600 TC, is there any reason for that particular rpms?

Thanks

Alan

 

[Edmond]

Rich,

Let us know how the install on the SR is. From the other posts I've read, they can be a PITA to install. I'm considering doing something like the SR next summer but if it's too complicated, I won't do it.

 

[vader86]

Would it make sense to do the rear end then the torque converter???

You noted 2400-2600 TC, is there any reason for that particular rpms?

Yeah it doesnt matter which you do first.

As for the stall, I believe anything over 2800 really takes some getting used to, the tranny will feel loose and like its not shifting right. That makes you nervous and drives you nuts.

Id probably run a 2400 or 2600 stall, just enough where you get good feel and still get good times. Which of those two you pick depends on how much you really want to drag race it. Either is easy to drive on the street.
The good thing about the vigilante converter is that they send it to you with whatever stall you want, and then you can have it changed once for free if you dont like it.
But, if this is just a drag car, you could put any stall in up to about 500rpm below your peak torque rpm. (that would be optimal for launching, but wayyy too much for street driving)

 

[oldace84]

Best for some quick 1/4 mile times.
Go for it. $$$$$$$$$$$$$$$$$
tony

 

[rrubel]

Edmund, I'll be happy to let you know how it goes. With luck, I'll be ordering the rest of what I need at Carlisle next week and will be starting work on it in the fall. It looks like the only really tricky part will be getting to some of the screws; I'm hoping to avoid the problem with some flexible screwdrivers I own (don't ask....); we'll see - they have a limited amount of torque they can take.

Before I rip the engine apart, though, I need to buy ported heads, rocker arms, and the roller cam retrofit kit.

Anyone got a spare or ported intake manifold they want to sell cheap?

[RICHR]

 

[Mad-Mic]

Vader,

i'm sorry but i don't see 3.07's to a 3.45 swap killing ET. it's not a dramatic jump like to a 3.73's or 4.11's. Rich will pick up .1-.2 in 60' and maybe .2 to .3 overall. is it worth it? not really. that would be the last thing i would do is do a gear swap. back when i had my gears put in my 82 Z i talked to my friend the shop owner about vettes since he was doing one. he told me the gear swap alone was 1000 bucks. i don't know what it is now but i still hear around 700-1000 bucks cause you got to drop the whole differential. to me thats not worth the money.

i have friends that run L98's in Camaro's and Trans Am's that run 3.73's with a 700R4 trannies and pick up .5+ tenths in the 1/4. the car will pull harder no matter what but your still shifting at 5k at the most in a L98 motor.

BTW for the other guys with Auto's if you decide to go with a Stall Converter you better put a Tranny Cooler in it! Stall converters that rev higher than stock packs alot more heat in a Tranny. 20 degree difference on average is the difference between getting 40k in miles out of a fresh trans to 100k+ 50 degrees your looking at less than 25k with a new tranny and i'm sure yours has miles on it already.