Ring and pinion recommendation??

undy · #1 (**permalink**) 01-13-2009, 08:32 AM

I've got a set of 373s in my Currie built Ford 9" and It's just too much gear for the car. I'm running the TKO600 with the 600 hp KC Pond 482 S/O. I've been on the edge for years now on getting a taller gear. I put her up on jack stands last night for her "winter overhaul" and found the clutch pack shot. I can spin one wheel and the other one doesn't move.. Well... that was the last straw. I'll replace the gear set and rebuild the clutch pack.

Question is... what gear should I run, 3.00 to 3.25 is what I'm thinking..

BTW.. no track durty, 100% street driven.

B.M.B.C · #2 (**permalink**) 01-13-2009, 08:48 AM

Undy
id be thinking about going about half way between the two, may something like 3.08 or slightly taller.

xlr8or · #3 (**permalink**) 01-13-2009, 08:57 AM

I ran a 3.31 with my FE/TKO600 combo and it was great. Easy to use around town and you know you have more than enough torque at any given time to roll on the throttle.

You don't need a 3.08 or taller as there is no point in gearing it for over 150mph.

undy · #4 (**permalink**) 01-13-2009, 10:26 AM

..forgot to mention.

I sort of messed up and got the .64 overdrive in the TKO600, which I thought was a good street match for the 370s. I think the 3.25s might be a better choice and still have an overdrive that's somewhat useable.

xlr8or · #5 (**permalink**) 01-13-2009, 10:52 AM

Yeah I had that too and only used it on the highway at 75-80 MPH plus. Then again my engine was happy to lope along at 2100 rpm because the cam wasn't too radical.
You can convert it to the .82 5th for about $600

Tom Kirkham · #6 (**permalink**) 01-13-2009, 11:02 AM

Undy,

I am a little confused. Why do you say that you have too much gear? 3.73 x .64 / .82 gives you an equivalent rear end ratio of 2.91 with a .82 o.d. transmission. I would think that if you are running a tire that has close to a 28 inch diameter that you should actually be pretty close. Any less gear and 5th gear will become more unusable. What size tires are you running? Are you sure you didn't get the .82 overdrive? If you can give me your tire size, RPM and speed in 5th gear I can tell you what overdrive ratio you have.

undy · #7 (**permalink**) 01-13-2009, 11:13 AM

Quote:

Originally Posted by Tom Kirkham

Undy,

I am a little confused. Why do you say that you have too much gear? 3.73 x .64 / .82 gives you an equivalent rear end ratio of 2.91 with a .82 o.d. transmission. I would think that if you are running a tire that has close to a 28 inch diameter that you should actually be pretty close. Any less gear and 5th gear will become more unusable. What size tires are you running? Are you sure you didn't get the .82 overdrive? If you can give me your tire size, RPM and speed in 5th gear I can tell you what overdrive ratio you have.

Hey Tom,

Cruise isn't the reason I'm saying "too much gear". It's 1st gear that's not useable. I just get rolling in 1st and it's already time to shift to 2nd. I had a 3.08 in a 496 powered 69 Stingray of mine with a Richmond 6 speed (similar 1st gear ratio as the Tremec) That 1st gear ratio was perfect out of the hole. I DO know what OD I have in the TKO600 as I'd spec'd it and got it new from Jimmy at Standard Tranny. I have access to all the ratio charts one could shake a stick at.

Dave

RodKnock · #8 (**permalink**) 01-13-2009, 12:50 PM

I'm running a TKO600 with the 0.82 5th gear and the Kirkhams's standard 3.42 rear gear and it seems just right.

jhv48 · #9 (**permalink**) 01-13-2009, 03:27 PM

With that much horsepower, I would run around 3.25 in the rear and change out the OD fifth to a more friendly number. If your powerband will allow it.

Mine runs about 2200 rpm at 80 MPH with a 3.73 rear end and a .64 OD fifth.
Would prefer a .82 OD as fifth gear is close to worthless if you don't want a 3000 rpm drop between fourth and fifth!

Great for cruising the freeway and mileage though if it doesn't fall outside of your powerband.

2KWIK4U · #10 (**permalink**) 01-13-2009, 04:31 PM

Undy
I switched out the 3.70's in my LS Currie to a 3.25 with the 0.82 and its perfect. We have almost the same engine config. and 1st gear is very useful. Use a mirror and get the stamped number of the top of the rear end housing and give it to Currie for the specs of the original build. My LS supplied Currie was build with the TrueTrac carrier. If yours has this, and I believe most LS's did, it does not have any clutches internally, and when you rotate one wheel, the other will not rotate or will rotate reversely, but is still a limited slip. See this link:
http://www.eaton.com/EatonCom/Produc...trac/index.htm

Brad W.

undy · #11 (**permalink**) 01-13-2009, 05:04 PM

Thanks everyone. I'll probably go with the 3.25s as suggested. I'm not going to pull the tranny so I'm (at least for now) stuck with the 0.64 overdrive. I am a little concerned though about the 325s making the 0.64 5th gear unuseable at "legal" highway speeds. My tire height is 25.8".

Brad, I talked to Currie today and they told me there was a TrueTrac carrier in it. I'll get the numbers off the housing tomorrow and call Currie to see if it's 28 or 31 spline. They thought it was 31 though.

Dave

Tom Kirkham · #12 (**permalink**) 01-13-2009, 07:23 PM

Quote:

Originally Posted by undy

My tire height is 25.8".

Undy,

Now what you were saying makes sense. The tire diameter was a crucial piece of information. Your 3.73 gears and 25.8 inch tire would be equivalent to a 4.05 gear with a 28 inch tire. Your 3.25 gear would be equivalent to a 3.53 gear with a 28 inch tire. You should be a lot happier with the 3.25.