Gforce Engineering Fabricated 9" IRS

[Irreverent]

What's the best center section option? I had a drag car once before that had a truetrac in it, it worked great but made a "linear" gear noise at 50+ MPH. I like this 9" kit, but it's got to be close to as quiet as the stock unit before I'll consider it.

[GFORCE1320]

Originally Posted by Irreverent

What's the best center section option? I had a drag car once before that had a truetrac in it, it worked great but made a "linear" gear noise at 50+ MPH. I like this 9" kit, but it's got to be close to as quiet as the stock unit before I'll consider it.

I'd go with the Strange Pro Iron case with a truetrac. The truetrac is a great all around posi for street and strip.
Or you can't go wrong with a Moser modular iron case with a wavetrac, more money but the wavetrac comes with a lifetime warranty.
We designed our 9" kit to bolt right in with the Strange Pro Iron case.

Thanks
Chris

[Wacker]

Originally Posted by Irreverent

What's the best center section option? I had a drag car once before that had a truetrac in it, it worked great but made a "linear" gear noise at 50+ MPH. I like this 9" kit, but it's got to be close to as quiet as the stock unit before I'll consider it.

No noise with the moser/wavetrac...You do have to do some minor metal trimming to fit that monster in there.

[Wacker]

Like I posted earlier the entire swap took about four hours, but I've done this before. It's actually harder to disassemble. Since the new axles come in multiple pieces, I took all the stock stuff out then put the suspension back together before any 9" stuff went in. Some of the pluses are ease of assembly and custom pieces. The minuses are: much heavier than stock, trimming of the cradle, and the custom tranny yoke requires you to cut off the little alignment stub on the output shaft. If you don't go with the custom yoke and use the adapter no cutting is required. I did not mind the mod, as I never plan on putting the stock carrier/driveshaft back in. I did/do have some driveshaft issues, but Chris is all over it and I expect it will be resolved this week. I do need to remove and tweak my exhaust as the big driveshaft and my three inch tubing are less than an inch apart in some areas. Overall I'm very pleased. It performed well at the track with no vibration and is very quiet going down the highway. I believe I buggered up an outer axle seal during install as I have a pretty good leak on the passenger side. I do plan on pulling the carrier back out this week to swap out the gears and fix the leak. The 3.5 gears are not aggressive enough for the NA car, a whole 3/10s slower compare to the 3.70s. I'm going to put in some 3.89s so I'll update when I run those.

[PwrAdikt]

Thanks wacker, that helps some with the gear selection I made. I went with the 3.70 n i was worried i went too low, especially since i just found out i'm gonna lose 20hp with the swap " which i didnt know"

[Wacker]

Originally Posted by POWERADDICT

Thanks wacker, that helps some with the gear selection I made. I went with the 3.70 n i was worried i went too low, especially since i just found out i'm gonna lose 20hp with the swap " which i didnt know"

Where is the power loss coming from? Are you referring to the power loss from turning the larger unit?

[StreetStrip]

Originally Posted by Wacker

Where is the power loss coming from? Are you referring to the power loss from turning the larger unit?

The 9" design is apparently inefficient due to the ring gear center line being relatively far away from the pinion centerline.

[Wacker]

Originally Posted by StreetStrip

The 9" design is apparently inefficient due to the ring gear center line being relatively far away from the pinion centerline.

Hmm...I'd like to research that, what are your sources? If that's true G-Force owes me a power adder worth 20 LOL!!

[StreetStrip]

Originally Posted by Wacker

Hmm...I'd like to research that, what are your sources? If that's true G-Force owes me a power adder worth 20 LOL!!

No scientific sources yet, but this sounds reasonable:

"The mechanical efficiency of a gearset will be at its highest when the ratio is at 1:1. This is because both gears have the same pitch diameter and the "sliding" of teeth is minimized, reducing friction.

The farther the ratio gets away from 1:1, the larger the difference in pitch diameter of the two gears. This causes much more tooth sliding, and as a result, more friction and less efficiency (and hotter differential fluid in this case).

Sometimes the same gear ratio in a different differential can be more or less efficient as well... Ford 9" rears are notoriously inefficient. This is because the pinion height is much lower relative to the centerline of the ring gear than it is in most rearends. The lower pinion height causes more sliding, more friction, and less efficiency.

In the Ford's case (no pun intended ), this makes the rearend stronger also, as the lower pinion height translates more force forward into the thrust bearing and therefore places less of a moment (rotational) load on the pinion shaft."

That was from here: http://www.z06vette.com/forums/f5/ca...-dyno-s-99548/

[Wacker]

Originally Posted by StreetStrip

No scientific sources yet, but this sounds reasonable:

"The mechanical efficiency of a gearset will be at its highest when the ratio is at 1:1. This is because both gears have the same pitch diameter and the "sliding" of teeth is minimized, reducing friction.

The farther the ratio gets away from 1:1, the larger the difference in pitch diameter of the two gears. This causes much more tooth sliding, and as a result, more friction and less efficiency (and hotter differential fluid in this case).

Sometimes the same gear ratio in a different differential can be more or less efficient as well... Ford 9" rears are notoriously inefficient. This is because the pinion height is much lower relative to the centerline of the ring gear than it is in most rearends. The lower pinion height causes more sliding, more friction, and less efficiency.

In the Ford's case (no pun intended ), this makes the rearend stronger also, as the lower pinion height translates more force forward into the thrust bearing and therefore places less of a moment (rotational) load on the pinion shaft."

That was from here: http://www.z06vette.com/forums/f5/ca...-dyno-s-99548/

I'd buy that, but gear ratio is going to play into this. Some ratios are just more efficient by design. It's one of the reasons I am switching to 3.89s vs going back to the 3.70s. I just hope the extra pull will get it back into the 11s. I know we are splitting hairs now, but I wonder how a high quality synthetic compares to a budget lube?

[StreetStrip]

Wacker, if you're increasing the gear ratio the efficiency will actually go down (increase in parasitic loss) because the pinion teeth are sliding more on the ring gear teeth. But, the increase in torque from the higher ratio should improve your ET.

[Wacker]

Originally Posted by StreetStrip

Wacker, if you're increasing the gear ratio the efficiency will actually go down (increase in parasitic loss) because the pinion teeth are sliding more on the ring gear teeth. But, the increase in torque from the higher ratio should improve your ET.

I guess that makes sense...

[GFORCE1320]

We now have 9" kits on the shelf ready to ship

I also have a couple Strange Pro Iron pumpkins with dyno time only that could be included with the kits at a discount if anyone is interested.

Thanks for the orders guys!
Chris

[Wacker]

Originally Posted by GFORCE1320

We now have 9" kits on the shelf ready to ship

I also have a couple Strange Pro Iron pumpkins with dyno time only that could be included with the kits at a discount if anyone is interested.

Thanks for the orders guys!
Chris

How is the new driveshaft coming? I will have the gears back Monday...BUSY week, but I'll try and get the old shaft in the mail.