5.13 gears for 8.8?

I was under the impression 4.88 was lowest available...

also told that 4.88 and 5.13 required a special pinion shaft...

anyone know anything about these?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33728&item=7963738199&rd=1

I'm running 4.88s in my 8.8 and it didn't require any special pinion shaft.

The special pinion shaft required might be a manufacturer specific deal...

I was looking at Motive Gear's Performance gearsets... and they state in their catalog that you need it.

Interesting...

Whose gears are you running?

I'm running Yukon 4.88s. Soon to be 5.13s as well. I looked at that ebay auction yesterday.

what's so special about the pinion shaft? of course it has to be different from the shaft for all the other ratios... so what is different besides the size/pitch/number of teeth? different bearing?

BrettM said:

what's so special about the pinion shaft? of course it has to be different from the shaft for all the other ratios... so what is different besides the size/pitch/number of teeth? different bearing?

Click to expand...

I dunno...

That's exactly what I was wondering...

This all it shows in their catalog...

Applies to 4.56 and down... except IFS

MOTIVE GEAR
PERFORMANCE R&P
MGP PART # OEM # TEETH RATIO
F888308 M4209F308 40-13 3.08
F888327 M4209F327 36-11 3.27
F888331IFS F75Z3222CC 43-13 3.31
F888355 M4209G355 39-11 3.55
F888355IFS F75Z3222BA 39-11 3.55
F888373 M4209F373 41-11 3.73
F888373IFS F75Z3222DD 41-11 3.73
F888410 M4209G410 41-10 4.10
F888410IFS 41-10 4.10
F888430 M4209G430 43-10 4.30
F888433 39-9 4.33
F888456* M4209G456 41-9 4.56
F888456IFS 41-9 4.56
F888488* 39-8 4.88
F888514* 36-7 5.14
*SPECIAL PINION SHAFT REQUIRED
ORDER MG# F8.8CSE - ’86 & DN OR F8.8CSL - ’87 & UP

Click to expand...

The pinion shaft is the cross shaft for the spider gears. Since it is a c-clip design and you have to get the cross shaft in an out with the diff in the housing you need a cross shaft that is notched.

The lower the ratio (numerically higher) the thicker the ring gear. Usually around 4.56's the ring gear is thick enough it starts to cover the hole for the cross shaft. I would think with 5.13's you would still need to grind some of the teeth down to get the shaft in even with the special notched shaft.

Funny, Yukon lists down to 6.14's for the 8.8 and Precision down to 5.13's. That axle has been around from the early 80's an mabye earlier. I wonder if part of them we not a c-clip design. My guess is if you wanted to use anything close to that you would need to get rid of the c-clips.

Lincoln said:

The pinion shaft is the cross shaft for the spider gears. Since it is a c-clip design and you have to get the cross shaft in an out with the diff in the housing you need a cross shaft that is notched.

Click to expand...

... or do some creative grinding.

That's something else I'd read somewhere in the rumornet...

Grinding down the stock shaft to get it to fit...

but then how much can you grind before you compromise it?

Just wondering if anyone has actually done this...

I'd PM CRASH, I think he has 4.88s in his 8.8, but he also installs gears and probably knows a lot about the different 8.8 issues.

Gil BullyKatz said:

... or do some creative grinding.

That's something else I'd read somewhere in the rumornet...

Grinding down the stock shaft to get it to fit...

but then how much can you grind before you compromise it?

Just wondering if anyone has actually done this...

Click to expand...

I've done it, but only for 4.56's which don't require that much. I'm lazy so it's much easier to pay them the $30 or so to just buy one.

Here's a pic:


and check out the instructions. They give you an idea on what needs to be ground:
http://www.ring-pinion.com/content/technicalhelp/default.asp?pid=126

The 4.56 ring gear was sooo thick I had to modify mine too. I also just ground the stock cross shaft down... just make sure you don't get it too hot and it won't hurt a thing! (You don't want to take the temper(sp?) out of it, I'm told)

Some hard wheeling and many miles later... no problems!

4.56 in mine. I used the stock cross shaft and ground just a hair off the inside edge of a tooth on the ring gear