installing 4.56 gears

[BARanger]

i am installing 4.56 in my truck with 7.5 it has the factory l/s it had 3.73 i reused all the factory shims and got .013 backlash what is the chance that you would reuse all the old shims and not have to change them

 

[Sasquatch_Ryda]

Sometimes you get lucky sometimes you don't. Is your pinion depth and gear tooth pattern check out good?

You backlash should be 8-12thou so I would try to at least tighten up your backlash a bit.

 

[-Nathan-]

that backlash is too loose. More than likely however, youre going to have to change out youre pinion depth, which in turn will require you to adjust your backlash anyway to bring it back into spec. More importantly is the pattern, run a pattern UNDER LOAD!!!! lots of people do not do this, and end up with an inaccurate pattern. Once you run a pattern, if you dont know how to adjust it, post a picture and well tell you what you need to do...if you cant figure it out.

Another thing... are these new or used gears? if theyre used than focus more on getting a good coast pattern...

 

[Hahnsb2]

I was thinking .015" was the max limit on the 7.5 backlash? Hell mine was around .020" and it was fine.

 

[BARanger]

i ran a pattern and from what i can tell it looks ok and they are neww gears. on the side of the ring gear it says bl .010 +.005

 

[Sasquatch_Ryda]

Ford spec for backlash is 8-12 thou. 15-20 is wayy too loose.

 

[-Nathan-]

Ford spec for backlash is 8-12 thou. 15-20 is wayy too loose.

Totally agree, and it will loosen up some as the gears wear in.

 

[Dweano]

that backlash is too loose. More than likely however, youre going to have to change out youre pinion depth, which in turn will require you to adjust your backlash anyway to bring it back into spec. More importantly is the pattern, run a pattern UNDER LOAD!!!! lots of people do not do this, and end up with an inaccurate pattern. Once you run a pattern, if you dont know how to adjust it, post a picture and well tell you what you need to do...if you cant figure it out.

Another thing... are these new or used gears? if theyre used than focus more on getting a good coast pattern...

Aaaand this is why you are helping me re-gear haha...I read that...but all I saw was words...zero comprehension

 

[Hahnsb2]

Most of the 7.5 backlash specs I'm finding online lists .015" as the max, including our own tech library, seriously .013" is just fine if the pattern is good.

 

[Sasquatch_Ryda]

I'm just saying what Ford published. While I agree that 1 thou difference isn't going to instantaneously kill it, they do make specifications for a reason.

 

[4x4junkie]

.008-.015" is correct, according to my Ford factory manual.

However I've found 8.8s end up with much better contact patterns at around .008-.010" BL. As similar as the 7.5" is, it's very possible this could be the case there as well.

 

[Sasquatch_Ryda]

Just went through the online manuals from 1990 to present, seems that the earlier ones called for 8-15 thou and the newer spec is 8-12 thou.

 

[4x4junkie]

I wonder if they lowered it some for the reason I found...

 

[Sasquatch_Ryda]

Very well could be. I always try to get my backlash as close to the lowest spec as possible. Either way, it seems anywhere from 8-15 is ACCEPTABLE.