Anti-spin with 3.73 gears - Opinions

[Big Boy]

I was thinking about upgrading my SRT8 Charger with the LSD Challenger rear diff and thought maybe getting the unit with the 3.73 gears would really be a great combo.

Are the Challenger LSD rear diffs for the 6sp Challeger R/T with Trak/Track Pak the same as the 6sp Challenger SRT8 with the Trak/Track Pak?

Is there any downside in running the 3.73 with my 5sp auto?

[PowerWagon896]

I was thinking about upgrading my SRT8 Charger with the LSD Challenger rear diff and thought maybe getting the unit with the 3.73 gears would really be a great combo.

Are the Challenger LSD rear diffs for the 6sp Challeger R/T with Trak/Track Pak the same as the 6sp Challenger SRT8 with the Trak/Track Pak?

Is there any downside in running the 3.73 with my 5sp auto?

That's an awful lot of gear for the NAG1. In 1st- 3rd gear, it would be like running a 5.26 axle ratio in a TH400.

If you run 31" rubber you will be OK.

If you want an idea of hi-way RPM, observe what you car does now @ certain hi-way speeds & multiply that by 1.22.

Example: If you are doing 2100 RPM @ 70 MPH on the 3.06 then you will be doing 2562 RPM W/the 3.73.

[Fargo59]

That's an awful lot of gear for the NAG1. In 1st- 3rd gear, it would be like running a 5.26 axle ratio in a TH400.

If you run 31" rubber you will be OK.

If you want an idea of hi-way RPM, observe what you car does now @ certain hi-way speeds & multiply that by 1.22.

Example: If you are doing 2100 RPM @ 70 MPH on the 3.06 then you will be doing 2562 RPM W/the 3.73.

simply put, youre going to launch with a crapload of torque in first, but run out of steam quick. gas mileage might not be soo great on the highway either. thats a whole lot of gear for an automatic like ours.

[stevesrt8]

3.73 is great for almost any other auto, but with our first gear it's only good for agricultural use (as in farming!).

[Dodgetony]

I am considering 3.23 or 3.55 with a lsd. With the 3.73 mine would have a 1st gear ratio of 13.39....which might be hard on parts.

[Big Boy]

Finally, a unanimous opinion about something on the forum. So, no 3.73 for my Charger.

I should probably start a new thread on this, but what would be the best bang for my buck, the Challenger LSD diff with the 3.06 or just keeping my SRT8 Charger rear diff and getting the 3.23 or 3.55 gears?

[Dodgetony]

Finally, a unanimous opinion about something on the forum. So, no 3.73 for my Charger.

I should probably start a new thread on this, but what would be the best bang for my buck, the Challenger LSD diff with the 3.06 or just keeping my SRT8 Charger rear diff and getting the 3.23 or 3.55 gears?

You and I are in the same boat. I am currently checking prices on the stock lsd 3.06 conversion versus a quaiffe and my gear of choice.

[PowerWagon896]

The 3.06 is a great ratio if you do not mind running small 26" drap radials for a stock displacement N/A application. That combo will go to 118 MPH before limp mode in 3rd gear "paddle hold".

For N/A big inch strokers or power adder stock displacement on 28" rubber it is near ideal giving a trap speed potential of nearly 130 MPH in 3rd gear if you can "paddle hold" 3rd to 6700 RPM.

For power adder big inch applications I would like to see the BuilderBill Detroit locker in a 2.93 ratio, but that is not available.

[Big Boy]

The 3.06 is a great ratio if you do not mind running small 26" drap radials for a stock displacement N/A application. That combo will go to 118 MPH before limp mode in 3rd gear "paddle hold".

Thanks for the great input on this topic.

It looks like I'll be putting the Challenger LSD with 3.06 gears into the Charger and the SRT8 rear diff ends up in my R/T Magnum.

Life is good ..........

[the plum]

I dont know where u guys get this stuf that a 3.73 is to low. to get the most u ned to go thrue the traps wound out in direct which is 4th gear so u should get to the finish line about 6000 rpm's and btw went to nascar in richmound last week got 20 mph on highway lost about 1 mpg. In city it gets 2 mpg better in city trafic. so much for the guys saying 3.73 is too low.

[PowerWagon896]

I dont know where u guys get this stuf that a 3.73 is to low. to get the most u ned to go thrue the traps wound out in direct which is 4th gear so u should get to the finish line about 6000 rpm's and btw went to nascar in richmound last week got 20 mph on highway lost about 1 mpg. In city it gets 2 mpg better in city trafic. so much for the guys saying 3.73 is too low.

The stock R/T 3rd gear FDR is 3.98:1, the SRT is 4.32:1 in 3rd gear & you claim you wind out to 6000 RPMs in 4th in the 1/4 mile W/a 3.73 FDR?

So are you trapping @ 134 MPH on 28" rubber or 122 MPH on 26" tires?

That's what you need to do to be @ 6000 RPMs.

I trap @ 6200 RPM @ 114 MPH on 28" rubber W/my 3.23s in 3rd gear W/an ET of 12.0.

I guess I don't have a clue about gear ratios.

Oh, BYW, I get 26 MPG on 3.23s @ 75 MPH on the interstate & it goes up to 28 MPG if I stay between 60 & 65 MPH on rural 2 lane ni-ways.

[stevesrt8]

oh boy, here we go again.

"Everybody" knows short gears make a car quicker. "Everybody" says they're better.

If you really believe this then it's true in your world. More power to ya!

But facts are still facts. The ole NAG has one hella short first gear in it, and if you're towing a big trailer maybe????

[PowerWagon896]

oh boy, here we go again.

"Everybody" knows short gears make a car quicker. "Everybody" says they're better.

If you really believe this then it's true in your world. More power to ya!

But facts are still facts. The ole NAG has one hella short first gear in it, and if you're towing a big trailer maybe????

Actually what I highlighted in your post is true. To a point.

What these guys are failing to realize is that once your car shifts into 4th gear you will be pulling a "taller"/"higher"/"numericly lower" final drive ratio than the guy W/306/3.23 gears pulling 3rd gear.

As far as 1st gear? W/the 3.58:1 1st gear reduction ratio you have nearly a 50% greater gear reduction than the typical 3 speed or 4 speed (3rd gear direct/4th gear OD) auto transmission.

W/some "ag" tires & a locker it would make a great tractor W/those 3.73s

I saw where 1 guy was tickled when he ran a 12.6 W/his 3.73s behind a NAG-1 in an SRT. That was proof (to him) that the 3.73 were a huge improvement over his stock 3.06 gearing.

12.6 in an SRT! I've seen plenty of near stock SRTs run that good on the 3.06s, even better W/< 26" drag radials.

[03HDFB]

The stock R/T 3rd gear FDR is 3.98:1, the SRT is 4.32:1 in 3rd gear & you claim you wind out to 6000 RPMs in 4th in the 1/4 mile W/a 3.73 FDR?

So are you trapping @ 134 MPH on 28" rubber or 122 MPH on 26" tires?

That's what you need to do to be @ 6000 RPMs.

I trap @ 6200 RPM @ 114 MPH on 28" rubber W/my 3.23s in 3rd gear W/an ET of 12.0.

I guess I don't have a clue about gear ratios.

Oh, BYW, I get 26 MPG on 3.23s @ 75 MPH on the interstate & it goes up to 28 MPG if I stay between 60 & 65 MPH on rural 2 lane ni-ways.

Really, the 3.73's aren't bad.....personally.....I'd say it was my best mod to date!! I'm running a full weight challenger 4500# and the 1st gear dig is perfect! Even the 20" Nitto DR's are handling the TQ at launch.....although it does take a good 7-8 seconds to warm them properly!
I'm trapping @ 5K right now, but as I add more power from the engine.... everything should pull to the left....shorter 60',quicker to 4th,higher RPM and speed at trap.
I'll post up as things change......Inertia Heads, Cam and intake are on the way! I guess I'll have to move to modified

[PowerWagon896]

Really, the 3.73's aren't bad.....personally.....I'd say it was my best mod to date!! I'm running a full weight challenger 4500# and the 1st gear dig is perfect! Even the 20" Nitto DR's are handling the TQ at launch.....although it does take a good 7-8 seconds to warm them properly!
I'm trapping @ 5K right now, but as I add more power from the engine.... everything should pull to the left....shorter 60',quicker to 4th,higher RPM and speed at trap.
I'll post up as things change......Inertia Heads, Cam and intake are on the way! I guess I'll have to move to modified

Your #s are great, but you would probably have done better W/26" drag radials on 3.06, trapping @ 6300 or more in 3rd @ 112 or so W/an ET of 12.2 or better. Not much better, but not worse either

You will have to trap over 130 MPH to pull those revs on the 3,73 on 28" rubber. That just ain't gonna happed W/O big inches & FI/or spray. Drop to 26" rubber & 125 MPH will get you to over 6000 RPM. You will need @ least 1 of the obove to do that.

Unfortunately the jump of available ratios from 3.06 to 3.73 leaves out all of the best ratios for the NAG 1, 3.23. & 3.31.