eatmyjeep

hey guys


I was looking a getting a 3rd member for my 9inch and i dont know whats best for me. I was looking at an open rear end and true trac. Maybe you can helP


My car. 1970 fastback

351w
TKO 500
thinking 350:1 rear gear
rack and pinion steering
track or street coil over front suspension
plans for body stiffing
Watts link ?

this car is a daily driver especially when it Rains bc on most nice days i just drive the motorcycles. What ive been trying to do is build a powerful car that handles great. Id like to spend more time in the mountains riding the twistys like I do on the bikes.

I guess my Question is ... Is a True Trac (LSD) my best bet for where im trying to go with this , or whould a True Trac be dangerous under these conditions.


What do you guys think??

zmetalmilitia

I went with the true-trac. I think it would improve safety by having an LSD that releases when needs to and engages when it needs to. These seem to be the best bet if you are looking for a LSD for street driving, at least in my opinion. I'm sure some will disagree.

Waffles

I've got a 408w with an AOD and 3.50s. It's pretty quick and the AOD makes it comfortable.

JMD

The first gear is pretty steep in a TKO500, I would say that a 3.50 is at the lower end of what you would want to make your first gear practical.

maybe 3.20s might be better.... (I KNOW a TKO600 and 4.11s make first gear not so great....)

1971mach1

I agree, 3.20 rear would be better. The TKO-500 has a 1st gear ratio of 3.27.
1st will definatly be like a granny gear in a truck with more than 3.50 rear gear.
For some perspective about 1st gear:
3.50 with a tko-500 is equivelent to having a toploader with 4.31 rear gear.
3.20 with a tko-500 is equivelent to having a toploader with 4.01 rear gear.
(assuming the toploader has a 2.46 first gear)

My Mach1 has a tko-500 with 3.00 rear and it's a good street combo but 3.20 would be perfect.

eatmyjeep

Your right 1st gear is low with 350's but not nearly as bad as i thought. Its not something i thought about after the first week.

My real Question Is. I want to drive the hell out of this car on whiny mountain roads. Up , Down , Left ,Right , and I need to order a new 3rd member... ( Is the TRUE TRAC (LSD) the right rear end for me? ) Or should i stick with a open rear end.

As driving though the mountains sometimes you run into unpredicted wet or sand patches.

1971mach1

If you hit the gas before the apex of the turn, the rear will slide out with open diff too,
so not sure it matters. I think LSD is mostly for straight line traction. But what do I know. I'm too chicken to push the limit on this stock suspension.
Maybe ask on a road racing forum.

eatmyjeep

Good Call! I checked out some road racing forums. It looks like there's a learning curve but everyone seems to be useing a true trac or trac loc. Thanks Mach 1

Gun Jam

I also use the true trac its great and I recommend it. It provides maximum traction in all situations turns or not and functions totally transparent when driven normally it doesnt click, pop, jerk, squeak,chirp or bark tires around turns and doesnt have a clutch pack to wear out...I have been running mine daily driven for about 3 or so years now never once an issue.

BUT as other have stated the car does handle much differently when traction is broken. Because the true trac provides maximum traction to both rear wheels when the torque applied to the wheels is great enough to exceed the traction generated by the rubber+surface then the byproduct is equal loss of traction. With an open diff one rear wheel would typically still be providing some traction as the spinning wheel produces a traction approaching zero (say 60% traction + 5% for 65% with the open diff) Again with the true trac both wheels would slip equally (so 5% + 5% for 10% total). The result is the car rapidly attempting to swap ends and requires rapid counter steer and quick smooth reduction of throttle.

The best advice is after having the true trac install and run in find an open safe place that is sandy or wet and get a feel for her I cant stress the importance of this enough...technically doing this in most cases would be illegal but sometimes doing the wrong thing is right..This is for sure one of those times.. You don't have to go fast 20 tops 15 is about right...but you need to know your horse.

-Gun

frdnut

I'm not sure what OD ratio you have but don't forget that as well when figuring out a rear end gear ratio..A higher rear gear might let you stay in first gear longer but may also make your overdrive useless unless you are into some very high speed driving....My brother is running a 4:11 rear with his T-5 and in OD it ends up being about the same as his stock toploader with a 3.0 rear gear..