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Old Jan 11, 2008 | 10:12 AM
  #1  
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Rear End Help

I am considering buying new gears and a locker for the rear differential on my truck. it is a 91 F-150 with the 300 I6 alls i know is that now at 70mph it is turning 2050 rpms (so i think it has 3.08's gearing now) and it is an open rear end. I know its eigther the 8.8 or the 9 but not positive. any advice is apreciated thanks
JB
 
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Old Jan 11, 2008 | 10:19 AM
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It is an 8.8, that was the only axle available in F150s of these years. For the ratio, check the tag on the differential, it should be held on by one of the bolts that attaches the dif cover.
 
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Old Jan 11, 2008 | 11:12 AM
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There's an axle code on the door pillar as well, that will decode to the gear ratio. I'd say it sounds like you have 3.55 gears now.. if your tires are stock or near stock size.
 
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Old Jan 13, 2008 | 06:51 PM
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thanks is it hard to do a gear swap on the 8.8? i heard the nines were supposed to be very simple
JB
 
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Old Jan 13, 2008 | 07:00 PM
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It is completely different from the 9 in. rear ends.
Either the whole truck goes to the shop or the whole rear end does.
The 8.8 is not a third member like the 9 in.

Take it in if it is a daily driver, a driveway swap may take time without the proper tools (but it has been done).
 
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Old Jan 13, 2008 | 07:25 PM
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If it's a 4x4 then make sure you also change the front gears to match.

And I agree with Paul here, 70mph at 2050rpms sounds like 3.55s or even 3.73s, but the latter is pretty uncommon on a stock setup.
 
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Old Jan 13, 2008 | 09:06 PM
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Shouldn't swapping the gears be basically replacing the ring and pinion gears? I've been researching this because I'm planning on going from 3.73's to 4.10's on my truck since I have 35" tires on it, and it is constantly kicking out of O/D on the highway when going overpasses. I know tearing apart the entire rearend is deep but all we have to really replace it the the gears, right?
Rick
93 F150 4x4 AOD 3.73ls 8.8 & Dana 44
 
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Old Jan 13, 2008 | 09:14 PM
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Originally Posted by pc_2000
Shouldn't swapping the gears be basically replacing the ring and pinion gears? I've been researching this because I'm planning on going from 3.73's to 4.10's on my truck since I have 35" tires on it, and it is constantly kicking out of O/D on the highway when going overpasses. I know tearing apart the entire rearend is deep but all we have to really replace it the the gears, right?
Rick
93 F150 4x4 AOD 3.73ls 8.8 & Dana 44
On the rear end -- yes. But if your truck is 4x4 (and it is) you also need to replace the ring and pinion in the front. And in your case, you're passing the 3.73 threshold for the carrier so you'll also need to replace your carrier (the housing for the spider gears). You will only need to replace the carrier on the front diff, the rear one will be fine with the 4.10s.

I also think that you're misunderstanding just how involved the job is. In order to replace the ring and pinion the entire differentials must be torn apart. Then once you get the new parts in, you need to shim the pinion and align everything correctly so your gears to hum and whine -- which will lead to severe damage. If you don't have experience in the field then I suggest paying someone to do it.
 
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Old Jan 14, 2008 | 06:36 AM
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Chris,
Thanks for the tip on the involvement. No I have never done it, but is a first time for everything. Besides, as I searched this site, I saw a pic of an invoice someone else had posted and the labor cost of $700+ floored me. I'm a very hands-on person and do 99% of my own work, so I'll take the challenge.
I'll let everyone know how it goes. This will be after the government reimburses me for using my money all year.

I just looked through Summit Racing for the carrier and I'm not sure what I need here. Does this look like what I need?
http://store.summitracing.com/partde...5&autoview=sku

Thanks in advance
Rick
93 F150 4x4 5.0SD AOD
 

Last edited by pc_2000; Jan 14, 2008 at 06:50 AM.
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Old Jan 14, 2008 | 09:52 AM
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That invoice you saw was mine
http://i170.-----------.com/albums/u...p/DSC00802.jpg

And yeah that carrier looks like it will work but it doesn't specifically say that it's high pinion/reverse rotation, which is what you specifically need for your truck. I recommend shopping on a site like Broncograveyard.com or Ringpinion.com, they have exactly what you need in a variety of brands and styles. Also, be sure to buy rebuild kits for both differentials, which includes bearings, seals, shims, etc etc. Trust me you'll want to replace all those things while you've got it torn apart. They can also be had at the afformentioned websites.
 
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Old Jan 14, 2008 | 11:36 PM
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Tack on another 800-900 for it where I live.

Front and rear R&P plus rear detroit locker and front true trac = 2600.00
 
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Old Jan 15, 2008 | 06:26 AM
  #12  
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From: Lutz, FL
Originally Posted by khadma
Tack on another 800-900 for it where I live.

Front and rear R&P plus rear detroit locker and front true trac = 2600.00
Khadma,
Holy *%@$ !! I'm definitely going to try it myself first. LOL

Chris,
I looked through Summit more (they are cheaper than Jegs, I haven't checked those sites you mentioned yet) and under the applications section, as I drilled down specifically to the F150 front that's the part they mention. So I'm guessing that should be correct. I'll check those sites you mentioned and see what they say. Thanks
Rick
93 F150 4x4 5.0SD AOD
 
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Old Jan 15, 2008 | 06:36 AM
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Check this link out. It will give you an idea as to what you are getting into.
http://www.angelfire.com/theforce/5o...5ohtech001.htm

There is also an instructional video out here on the web. Check ebay or do a search. I hear it's a must for the first timers.
 
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Old Jan 15, 2008 | 07:47 AM
  #14  
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From: Lutz, FL
Originally Posted by alz
Check this link out. It will give you an idea as to what you are getting into.
http://www.angelfire.com/theforce/5ohcpa/cpa5ohtech001.htm

There is also an instructional video out here on the web. Check ebay or do a search. I hear it's a must for the first timers.
Thanks for the link. Know of any out there for the Dana 44? They should be similar right? LOL
 
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Old Jan 15, 2008 | 01:10 PM
  #15  
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Here is a video. It covers them all.
http://www.technicalvideos.com/video...erential.phtml

I've never personally done this work. I only found the link for you. I have used the other site to rebuild my Trac-Loc though.
 
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