Thread: Buying a new 9 inch 3rd member. What do you recommend?

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This truck was set up for drag racing with a Ford 9 inch and 4:11 gears. Strange Engineering 31 spline axles. Driveshaft looks new. Tranny is brand new TCI Street Fighter T350 with TCI 2500 torque converter. Engine is a 383.

I have no intention of drag racing or running for long periods of time on the HWY. Weekend running around and cruising around time. Dust the occasional stop light challenge.

I have already found two broken roll pins inside the rear housing so I am expecting damage.

If I were to go with a new unit what do you recommend?
Posi or not?
Gear ratio?
Company to buy from?

The oldest kid on the block is Currie Enterprises. 714-948-2600
A good choice in my opinion would be a posi 3.73

Another trusted name is Moser Engeneering, Mon.-Fri. 8-5 EST 260-726-6689

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Do you have an idea of how many rpm you want to turn?
You'll need to know the OD of the rear tires too. Are you staying with what looks like slicks in the rear?
I don't know if you've posted what cam the motor has because you'll need to stay in the working range for the cams rpm ..
There are many estimators online. drop in the tire size and the gear selection and it'll tell you the rpm you can expect.

I would recommend a Detroit True-Track center section. I run a Detroit True-Track in my '32, and like it a lot. It is like having an open rear end until you lean on it and both rear tires grab. It has worm gears so there are no clutches to wear out. If you are running pro-street tires and plan on burnouts and hard launches, I'd recommend a Detroit Locker. But as far as gears, you are going to have to figure out at what rpm you wish to cruise at with the size of your rear tires. There are online calculators like Denny posted to help you figure it out.

your never going to hook up. why spend a ton on something you dont need ? there are plenty of ptracts in the salvage yard .

At least he'd be spinning both sides instead of just one

I've gotten all my 9" stuff from these guys. They build a lot of them and do great work and have awesome customer service!

https://www.quickperformance.com/Com...ons_c_558.html

They have many choices for you to choose from.

Originally Posted by 34_40

Do you have an idea of how many rpm you want to turn?
You'll need to know the OD of the rear tires too. Are you staying with what looks like slicks in the rear?
I don't know if you've posted what cam the motor has because you'll need to stay in the working range for the cams rpm ..
There are many estimators online. drop in the tire size and the gear selection and it'll tell you the rpm you can expect.

Not sure of RPM. I replaced the slicks with 275/60/15 tires which I believe are 28 inches tall. I do not know the cam numbers as engine was put in by previous owner. I think I will stick with 4:11 as I won't be doing a lot of HWY time in this truck. Around town. on weekends and shows but no long trips.

Originally Posted by 40FordDeluxe

I've gotten all my 9" stuff from these guys. They build a lot of them and do great work and have awesome customer service!

https://www.quickperformance.com/Com...ons_c_558.html

They have many choices for you to choose from.

Actually just got off the phone with these guys.

I like the idea of a pozi that acts like open until you need it.

Pozis are annoying on the street. They "cone" the tires, wearing them to the insides. They "hop" and "klink" in turns. Quite useful when you need them, but annoying when you don't.

I have a local Driveline place that will install a new Yukon Duragrip posi unit with new bearings for $650. I'd have to install the ring gear and put it back in the truck.
Not sure if that's a good price or not.

Judging by the prices I see on this page... I'd say no.

https://www.summitracing.com/search/...20Differential

I did use the additive. Just will never be as smooth as an open end.

I'd say that's a pretty high price considering they aren't even setting the gears up. Call Quick Performance again. They build center sections too.

Ended up buying a new 3rd member with 3.91 gears and Eaton Truetrac. I made the purchase through Quick Performance. They had the best price and excellent customer service. Thanks for all of the advice given here in this forum.

On to the brakes.