Beefy up a rear end • The Dodge Challenger Message Board

by **72 Challenger (Hans)** » 23 Oct 2003 17:16

Any ideas on how to beefy up the 8.3/4 rearend besides bracing the housing? I like to let live the rear for a while. thx!

by **dave-r** » 23 Oct 2003 23:22

Unless you plan on running 10s or less don't bother.

by **dave-r** » 24 Oct 2003 7:34

If you plan any NOS though it needs to be beefed up because of the huge torque off the line.

Which third member (diff) are you using? The bigger pinion the better of course but they are all strong bits of kit. Stronger axle shafts might be the first place to start.

My axle is completely original except for the gear in there. No problems so far and it is a very heavy car. Only running 1.7 60ft times at the moment though.

by **72 Challenger (Hans)** » 24 Oct 2003 8:33

Bottles are for babies, so no NOS I guess. Just like to run low 11's on a normally espirated BB in a stock body.

I have two diffs laying around, both 742 casings and rebuilt. A 3.91 and a 4.30 which I use now and also later with the 440.

A 1.7 60ft seems a bit to slow for your engine Dave, till what rpm are you stalling at the line? My 340, stalling at 2900rpm already runs 1.8's in the 60ft. Only with this 60ft I 'only' run 13.4's at the end.

by **dave-r** » 24 Oct 2003 9:50

I don't know what rpm it loads up to because Linda does the converter loading thing. I prefere to stamp on it from idle so that I get the full pump shot and I am too busy at that point to look down at the tach. Both seem to give about the same result but we need to do more experiments. I suspect it will rev no higher than 2,500 - 3000rpm. Holding it on the brake is the hard bit. I will see how high it stalls next time i have it running. I am still in need of a new fuel bowl and the one I was promised has not turned up.

A higher stall converter will work better with this engine but would spoil the street driving. A 4.5 rear gear would be better for me too if it was just a race car.

Low 11s will be hard on the axle. Borderline I would say. I know there are people out there that would say it will break for sure. But there will be others that say they run 10s on a stock axle no problem.

If you have the money get some better axle shafts and some beefy diff parts from Randy's R&P. Otherwise run with the axle as is and see what breaks (if anything). With a lot of runs i guess something will go eventually. But that might be quite a long time.

by **72 Challenger (Hans)** » 24 Oct 2003 10:00

Dave, with your overdrive unit it shouldn't a problem running 4.56's in the rear w/ 28" radials. With my 4.30's I just drive to the strip and after the event back home without problems. Just take your time when running about 3500rpm@60mph. No probs.

We'll see when it breaks, anyway to run low 11's with all the weight to carry on I need to built a brute engine so it will propably turn out in running around 12flat. If it breaks, I can at least say I have the power to break the parts

by **dave-r** » 24 Oct 2003 12:00

I don't really want to go to a lower gear. I have a 150mph speedo in the dash and it is a nice thought that I still need it to go that high. The car is fast enough on the strip. I don't want to keep making it faster. I just want it tuned as well as possible.

You are going to need something like 600hp to run low 11s which is asking a lot of a nornally asperated street 440 unless it is built with a lot of trick (expensive) parts.

by **72 Challenger (Hans)** » 24 Oct 2003 12:14

Well. see the engine section for the plans Dave.

I'm never able to run the 150mph here Dave, way too busy on the roads. 70 is the max most of the time. Except for driving through the night though.

by **dave-r** » 24 Oct 2003 12:17

I've only been up to about 130 in her so far on a road I know well. It goes from 40mph to 120 in only a few seconds which is nice for overtaking.

by **Christer** » 19 May 2004 17:40

Rather embarrassing to be in front of the crowd with these kind of problems.... :wink:

Lucky me, that I don´t have that much ponies.

by **Tim** » 20 May 2004 12:27

Do you reckon you'd need aftermarket halfshafts on just a small shot of spray Dave? I heard if you don't purge the system before it's activated, you get a softer hit off the line.

Just curious :wink:

by **dave-r** » 20 May 2004 12:43

I know NOTHING about NOS.

However it does increase torque off the line a hell of a lot. It is really down to how much you use and how good the bits are you are starting with.

No purge will indeed give you a softer launch but it depends on how much has evaporated in the lines etc. and as the extra fuel will still be going it I expect it could bog or something?

I wouldn't touch the stuff myself.

by **Tim** » 20 May 2004 15:17

Yeah, sounds right Dave. If you compare the before/ after numbers for a simple plate system, the 60ft time increases, but the overall ET decreases.

I suppose the longer 60ft times could be partially due to loss of traction, but I think you get a momentary stutter before the pure nitrous hits your motor. Not a bad thing if you're running on street tyres, or a lightweight drivetrain.