86 Camaro/350/650 Holley/Headers/ Mild Cam/700R4; Thinking of going to a 3.78 from a 2.78.. Not a dailey driver (225 miles last year) Take to drag Strip once in awhile (run strret class for fun). Just trying to go alittle faster. Anyone have any thoughts, good or bad. Thanks

 

Never heard of any such ratios...

Gear ratios are 2 whole numbers (tooth count) divided by each other. They only make certain ones, generally where at least one of the 2 #s is a prime. 3.73 for example is 41 and 11. That's most likely what you'll be able to buy.

Most likely you have 2.73 now (41 & 15). You'll have to change your carrier as well, or buy the "special" thick gears, or use a spacer.

That said, 3.73 gears will make it feel like you just bolted in 100 more cubic inches. Tends to be a little too much with a 700 because 1st ends up being SO short... you'll be red-lined before you can even tell the car has started moving. Other than that, why not. Although, 3.42 is usually a better deal with that trans, on the street.

 

No such ratio for 3rd gen 10 or 9-bolt rears. What rear do you have now???
2:73 = 10-bolt
2:77= 9-bolt

both the above are 2-series carriers,

 

I went from a 2.73 ,26 spline 2 series open differential to a 3.42 , 28 spline 3 series Eaton Posi./ L.P.W.suport cover. with the 700r4 and a corvette servo upgrade and the difference is night and day. For my 5.0 it really woke it up. EDIT = Sorry, I jumped the gun. If its for racing only I'm not qualified to say. I can suggest the cover I have, it is top of the line.

 

It would depend on if you were running 1/8 or 1/4. If it was a toy and not a dd I would say 3.73 or steeper

 

Sorry guys I knew it was 2.73 and 3.73, senior moment. I have a 10 bolt with posi. i was not aware that the carrier would also have to be changed. Could someone tell me the purpose of the carrier and why it needs to be changed.
I run 1/8 mile, yes, first gear will run out fast, thats one reason I was looking for input from someone that has been there. Thanks

 

A lot of info below that you may find interesting:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

Long story short, higher ratio gears have the mounting flange in a slightly offset location. You'll need a 3-series carrier to place 3-series gears in the correct location in the housing.

The carrier is what the gear attaches to taht converts the rotation of the gears into rotation in the axles. Both axles are inserted into the carrier.

 

How mild is the cam/heads setup and how big of a tire? 3.42's fits best with MOST combinations in the 700r4.

I did a 2.73 to 3.73 switch on my LS1 car and was dissappointed. Only gained a tenth so far and 1mph. Feels fun in first, but I do miss that highway gear for my daily driver.... lost 3-4mpg already.

Some cars respond to gear some dont. My L98 picked up a few tenths and few mph just by switching from 2.77 to 3.27's. Picked up alittle more with 3.42's


Does your car have a torque converter? If not, I'd get a 2800-3000 stall or so depending on your heads/cam setup, and let it eat. You'll notice a much better gain for your money over a gear swap.

 

A gear change for your car is more involed then you think. For example: Gear set, LSD 3-serries carrier, 28 spline axle shafts, misc parts and since it is not in most cases a DIY tyoe job..Labor. You are looking at about $1000 in round numbers.

 

I have a guy who builds drag cars top to bottom who said he would sit up the gear, that said he never mentioned a carrier and I never ask. I am capable of doing the remainer. Would I have to switch to 28 spline or is that just money spent well.

 

Oh, when i purchased the car the owner said he had a stall converter installed. Not sure? I have looked at the converter from the inspection cover, ity appears smaller than normal, but what is normal for this car. Anyway of telling for sure

 

You wont need a carrier as long as you buy a 3.73 ring set designed for the 2 series carrier. Thats what I have in my 99 TA's 10 bolt rear.

Wont need axles either unless yours are bent. Would be a good idea tho to change the axle bearings and such. get a deluxe pinion/gear install kit with new bearings.

See if you can measure the diameter to get a rough idea on size. For stall speed, try to do this. From a dead stop/idle rpm and in gear, mash the throttle to see how high the rpms rise before the car starts to move or spin tire. This is "flash" stall and will give you an idea of how high the stall speed is on the converter.

 

Thanks for the info, I misunderstood the other post. Thougth gear set for series 2 was 3.08 and down. You are saying that I can get a 3.42 or 3.73 for a series 2?

Stock converter diameter??