Rear-end/diff question

bcbickers · #1 12-02-2002, 11:34 AM

Hi Everyone,

I have an '01 Expy with the 4.6L and am setting it up for better performance and eventually towing. It just got its first mod: Dynomax catback. Major improvement! Power delivery is much smoother, no loss of low end torque, picked up a few at the top end, and it sounds great!

Anyway, I have the 3.31 open rear and am looking to swap in a 3.73 LS. Just a few questions:

1) It should be an 8.8", right?
2) Should I go with a factory Trac-Lok or something else? I have no interest in an Auburn, since it's a throw away. Eaton or Powertrax. seem to be popular. Anyone have these units?

Thanks in advance for all of the input!

jimmsimm · #2 12-04-2002, 01:11 PM

Your rearend should be a 9.75" and if you are a 4x4 the front is an 8.8".

Why don't you try to find a wrecked Expy with the 3.55 or 3.73 LS differential and then swap them out.

H6 is a 3.73 LS
H9 is a 3.55 LS

00expo · #3 12-04-2002, 02:01 PM

I have a 5.4L, 4.10 gears with factory LS rear (9.75) and Eaton front LS. I had stock 3.55's. Before getting blown, I wished I'd gone to 4.30, even with a 5.4L. If you're going through the expense of a gear swap, I'd do the 4.10, especially with the 4.6L. This gearing hits the sweet spot of the power band, and does not noticably affect gas milage. You will, however need a chip to correct the speedo / odometer for the new gear ratio difference.

In my opinion the expy should have had 4.10 as an option.

But than thats only my .02c !

DJkinko · #4 12-05-2002, 06:25 PM

I have a 9.75" 373 gear LS Rear End available. It was taken off my Y2K Expedition, at 12k miles. It's available cheap, but Im not sure what trucking it from LA, CA would be like...

tysonxj · #5 12-11-2002, 02:42 PM

If you have the 4.6 you should have the 8.8. I do on my '99. I am swapping in a 9.75" with 3.73 and LS that I bought cheap. I haven't figured out if I need a shorter driveshaft with the 9.75". Anyone know if the lengths of the 4r70 and the 4r100 are similar?

MKTRUCK · #6 12-22-2002, 09:56 AM

Djkinko,

I emailed you using the forum feature. If it doesn't work, then I hope you subscribe to this topic.

I am interested in your diff. Questions first.

Mike Kievit

emk113@aol.com