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Speed Holes
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5,190 Posts
Discussion Starter #1
I would think this would be a fairly common set-up.... and I'm thinking of doing the same.
I'm already running the Detroit TrueTrac out back but with my factory 3.73's and a fresh install kit, but now want to up that to 4.56's front and rear (I have 4X4).

But, what kind of concerns me is just today while looking around I saw this post:
post in Performancetrucks thread about Motive 4.56's and TrueTrac

If you don't want to click that link it says (most importantly what I highlighted there):

"I'm gonna be doin the swap in the next few weeks,I thought I would go ahead and swap in the 4.56 gears this weekend and ran into a few snags.1. I bought the gears and tru-trac from summit motive 4.56,s summit install kit they said I needed a diffferent bearing than was in the kit,ratech carrier bearings cant remember the part# but it was the wrong damn bearings. I came to find I just needed stock carrier bearings and races-99 nbs silverado.I also tried to reuse the stock pinion shim but it didnt seem to give me any preload on the rear pinion bearing, I'm gonna try and get a new chrush sleeve tues. and try to finish the gear swap.Swapping gears is not a fun job!!! Also if you buy the tru-trac and bolt 4.56 gears on it the friggin cap that goes over the hole in the unit wont work with 4.56's(gear is too thick) i had to get the porta band and cut part of the cap so it would slide past the gear.Its held in with a snap ring so it dont think it will hurt.This is how far I have got so far maybe better luck next week."






So now I'm wondering what's the deal?
Is it Common to have mounting/compatibility problems with running 4.56's with the TrueTrac?
Is it just those brand gears or what?

Should I get Motives, or Yukons? Any other recommendations?


Right now I'm thinking of going with the Motive 8.25IFS 4.56 up front and a new install kit, and Yukon 8.5/8.6" 4.56 out back, but thinking of reusing the install kit that was used about 1500mi. ago to install the TrueTrac. You think that would be a problem? I wouldn't think so, but I don't know otherwise.
Or should I just go with Yukon in both front and rear, or Motive in both front and rear???

I'm looking on ronsmachining on ebay, where I originally bought my truetrac awhile back.

Help me out before I do some impulsive clicking without knowing! :crazy:




Also, just to ask, anyone know if I'll have issues running my TA Performance girdle with the 4.56's? I wouldn't think so, but just want to bring that up incase it may be an issue.
 

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GMFS Military Member
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should be ok on the Girdle, i plan to run mine on my 14SF with my 4.88s
 

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go with yukons, they cant be beat
 

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Speed Holes
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5,190 Posts
Discussion Starter #5
im running 4.56 (genuine) w/ a true trac....but i didnt do the install

so the installer didn't make you aware of any complications?

Also, just curious, what diameter tires are you running there? are those 35's? How is it with 4.56? you run much on the expressway?



Thanks for the input guys!
But, I'm really looking for some specifics... before I drop the coin on an order I want to make 110% sure I'm getting what I need and want.


on a side note, I'm getting a little bit of seepage leak from one of the studs on my TA Perf girdle... gonna have to look at that a bit more tomorrow....
 

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he didnt say he had any problems..... as far as tires yes they are 35's and 20's. I drive a decent ammount of expressway...... at about 80 im at 2500 ish rpm.
 

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seepage from the stud on the cover??? :eek: keep us updated! I havent ordered mine yet lol.
 

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ive ran 488s with my 14 bolt no issues now im down to 410s with a truetrac

no issues on install. pretty simple actually
 
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