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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » Fully Assembled Third Member Swap?

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    6/15/2022 1:27 PM  #1

    TremendousWand
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    Registered: 5/16/2013
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    Fully Assembled Third Member Swap?

    I want to change gears from stock 2.8 to 3.55.  I don't want to upgrade to a 9" rear, I just want to swap center section (third member) in the 8 inch.  Quick Performance sells a fully assembled 'drop in' 3.55 third member with the limited slip for around $950.  From what I read, just swapping the center section can be done in an afternoon.  

    Looks like it's a matter of pulling the axles, removing the old center section, cleaning out the old fluid, install the new section, fluid, axles and break it in.  Anyone done this?

     

    6/15/2022 1:46 PM  #2

    Rudi
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    From: Stuck in the 50's Welland Ca
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    Re: Fully Assembled Third Member Swap?

    When I changed from 2.8 to 3.25 I did it with the rear end out of the car, but basically it’s the same process.
    I would also check the rear bearings and at least put in new seals.

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    6/15/2022 2:51 PM  #3

    MS
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    From: Canyon Lake, Texas
    Registered: 1/24/2013
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    Re: Fully Assembled Third Member Swap?

    Check SPEEDWAY.  I am very happy with the one I bought from them.  Traction lock with ratio of choice for under a grand.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    6/15/2022 4:13 PM  #4

    Alan
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    From: Axtell KS
    Registered: 4/03/2013
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    Re: Fully Assembled Third Member Swap?

    I went from 4:30 to 3:70s. 9" trac lock. Hardest part was putting the chunk back in the rear end. Had it on a lift and lifting 80# chunk 6' in the air and lining up the bolts was a little more than one man should do.

    67 Coupe, 5.0 EEC IV Fuel injected. T5, 3:70 rear
     

    6/15/2022 4:18 PM  #5

    lowercasesteve
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    Re: Fully Assembled Third Member Swap?

    As long as everything is apart, change out the outside axle seals.  It's fairly easy to do.  I've had problems with sealing if I reuse old seals.

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/15/2022 4:21 PM  #6

    lowercasesteve
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    Re: Fully Assembled Third Member Swap?

    lowercasesteve wrote:

    As long as everything is apart, change out the outside axle seals.  It's fairly easy to do.  I've had problems with sealing if I reuse old seals.

    Whoops!  that's well covered in your other post
     

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/15/2022 4:38 PM  #7

    Nos681
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    Re: Fully Assembled Third Member Swap?

    TW it gets very complicated, the WYIAT MONSTER will find you. 😜

     

    6/15/2022 5:25 PM  #8

    TKOPerformance
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    From: Newark, DE
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    Re: Fully Assembled Third Member Swap?

    Always a good time to do bearings and seals.  I'd recommend a Lube Locker gasket found here instead of silicone:

    https://www.lubelocker.com/products/ford-9-axles-llr-c900

    I just started using these and they are WAY easier and less messy than silicone.  They are reusable too.  I used one on the 10.5 in my F250, then changed the gear oil at 500 miles and reused it with zero issue or leaks.

    Make sure you keep and reuse your copper washers for the nuts. 
     

     

    6/15/2022 7:07 PM  #9

    Rudi
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    From: Stuck in the 50's Welland Ca
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    Re: Fully Assembled Third Member Swap?

    ^^ That gasket is for 9”, do they have one for 8”?

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    6/15/2022 10:29 PM  #10

    BILLY WALTON from GEORGIA
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    Re: Fully Assembled Third Member Swap?

    Lets say you get the section MS mentioned what is a normal price a shop would charge to install it?

    Its really me....I fixed my caps lock .
     

    6/15/2022 10:41 PM  #11

    BILLY WALTON from GEORGIA
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    Re: Fully Assembled Third Member Swap?

    MS wrote:

    Check SPEEDWAY. I am very happy with the one I bought from them. Traction lock with ratio of choice for under a grand.

    I only seen options for 9 inch.

    Its really me....I fixed my caps lock .
     

    6/16/2022 5:58 AM  #12

    TKOPerformance
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    From: Newark, DE
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    Re: Fully Assembled Third Member Swap?

    Rudi wrote:

    ^^ That gasket is for 9”, do they have one for 8”?

    Yes sir, sorry, wrong link.  Is here:

    https://www.lubelocker.com/products/ford-8-llr-f800

    They have these for most rears, even Japanese trucks and cars.  From now on I'll check to see if they make a gasket for whatever I'm working on before diving in. 
     

     

    6/16/2022 7:50 AM  #13

    TremendousWand
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    Re: Fully Assembled Third Member Swap?

    MS wrote:

    Check SPEEDWAY. I am very happy with the one I bought from them. Traction lock with ratio of choice for under a grand.

    I also only see 9 inch third members on SPEEDWAY.  Maybe they used to carry them.

       •Thread Starter
     

    6/16/2022 7:58 AM  #14

    TremendousWand
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    Re: Fully Assembled Third Member Swap?

    Looks like 'Quick Performance' is the only place I see that has the 8 inch complete member ready to drop in.  I'm just rebuilding/ cleaning up everything else.  The price difference between the Posi and TruTrac are about $300.  Which puts the total price including shipping at about $1300 if I went with the higher price diff.  I'll install new bearing and seals on the axles but keep the stock 28 spline.  This isn't a track monster and tires are too expensive to be burning rubber.  

    On a side note... one crazy thing about having 10-15 years of internet post on mustangs available is you an see price increases.  I see old post from early 2000s on other forums where people quote parts for half of what they are sold at now. 

       •Thread Starter
     

    6/16/2022 8:15 AM  #15

    Steve69
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    Re: Fully Assembled Third Member Swap?

    I went the Quick Performance route with there 9" center section last year.  I went with the Eaton Truetrac with
    a 3.25 gear.   Mine works great.  I did there break in which was drive 5 miles let it cool off like 3 times before you take it for a longer trip.  I welded a add and drain the oil plug in housing also.  I had my axle housing out which made it easier.  

    Steve69

    Last edited by Steve69 (6/16/2022 8:16 AM)

     

    6/16/2022 9:20 AM  #16

    TremendousWand
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    Re: Fully Assembled Third Member Swap?

    Steve69 wrote:

    I went the Quick Performance route with there 9" center section last year.  I went with the Eaton Truetrac with
    a 3.25 gear.   Mine works great.  I did there break in which was drive 5 miles let it cool off like 3 times before you take it for a longer trip.  I welded a add and drain the oil plug in housing also.  I had my axle housing out which made it easier.  

    Steve69

    If I'm not mistaken, you are supposed to drain the diff fluid after 500 miles.  I don't want to take all this apart again so I was thinking adding a drain plug to the 8 inch housing to make the job easier.
     

       •Thread Starter
     

    6/16/2022 11:21 AM  #17

    lowercasesteve
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    Re: Fully Assembled Third Member Swap?

    TremendousWand wrote:

    Steve69 wrote:

    I went the Quick Performance route with there 9" center section last year.  I went with the Eaton Truetrac with
    a 3.25 gear.   Mine works great.  I did there break in which was drive 5 miles let it cool off like 3 times before you take it for a longer trip.  I welded a add and drain the oil plug in housing also.  I had my axle housing out which made it easier.  

    Steve69

    If I'm not mistaken, you are supposed to drain the diff fluid after 500 miles.  I don't want to take all this apart again so I was thinking adding a drain plug to the 8 inch housing to make the job easier.
     

    I use one of those pumps that you use to fill the diff.  Turn it around and you have a suction pump to empty the diff in place.
     

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/16/2022 4:24 PM  #18

    BILLY WALTON from GEORGIA
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    From: CARROLLTON GEORGIA
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    Re: Fully Assembled Third Member Swap?

    What does a shop normally
    charge to install labor wise?

    Its really me....I fixed my caps lock .
     

    6/16/2022 5:23 PM  #19

    Rudi
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    Re: Fully Assembled Third Member Swap?

    BILLY WALTON from GEORGIA wrote:

    What does a shop normally
    charge to install labor wise?

     
    Around here 80- 100 an hour.
    Guys that know what they are doing ask for more.
    YMMV

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    6/16/2022 7:07 PM  #20

    Raymond_B
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    Re: Fully Assembled Third Member Swap?

    I used a Lubelocker when I did the 8.8 in the Lightning, high quality product.

     

    6/17/2022 9:03 AM  #21

    Steve69
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    Re: Fully Assembled Third Member Swap?

    TremendousWand wrote:

    Steve69 wrote:

    I went the Quick Performance route with there 9" center section last year.  I went with the Eaton Truetrac with
    a 3.25 gear.   Mine works great.  I did there break in which was drive 5 miles let it cool off like 3 times before you take it for a longer trip.  I welded a add and drain the oil plug in housing also.  I had my axle housing out which made it easier.  

    Steve69

    If I'm not mistaken, you are supposed to drain the diff fluid after 500 miles.  I don't want to take all this apart again so I was thinking adding a drain plug to the 8 inch housing to make the job easier.
     

       I had called them and asked them if that was necessary and they said no.  They were strongly for doing the warm up cool down though.  
     

     

    6/17/2022 10:48 AM  #22

    TKOPerformance
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    Re: Fully Assembled Third Member Swap?

    Having seen what ends up in the oil after breaking in about a dozen rebuilt rears I would say change the lube at no more than 500 miles.  The oil gets contaminated with metal flakes, the coating on the gears, etc.  I've always changed the lube after a break in period. 

     

    6/17/2022 1:27 PM  #23

    lowercasesteve
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    Re: Fully Assembled Third Member Swap?

    TKOPerformance wrote:

    Having seen what ends up in the oil after breaking in about a dozen rebuilt rears I would say change the lube at no more than 500 miles.  The oil gets contaminated with metal flakes, the coating on the gears, etc.  I've always changed the lube after a break in period. 

    I agree.  Why not? it's easy to do and can be done as fast as an oil change.
     

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/17/2022 3:03 PM  #24

    Rudi
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    Re: Fully Assembled Third Member Swap?

    Does Ford or any of the other manufacturers require drain and fill on new vehicles on the 1st 500 miles?

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    6/17/2022 5:14 PM  #25

    lowercasesteve
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    Re: Fully Assembled Third Member Swap?

    Rudi wrote:

    Does Ford or any of the other manufacturers require drain and fill on new vehicles on the 1st 500 miles?

    Don't know about rear ends, but I've had new cars require an oil change at 500 mi.  I think even my '15 GT had something like that.
     

    Original owner - 351w,T-5, 4whl disks, power R&P
     

     

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