Changing rear ratios

Drivetrain discussion including Transmission, Differential, Driveshaft, and related items.
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elc32955
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Re: Changing rear ratios

Post by elc32955 »

I'm going to preface this by saying I don't have all the answers, so I'm gonna lean on Chris and the G8 folks to discuss the diff swap technicals a little more as this one has been extensively bandied about in a number of other forums. Physical size and increased durability is gained by the swap to the Camaro diff to start with. GM has recognized the Camaro is used in racing and put some maintenance callouts in accordingly. Lord knows cops never race their patrol cars :)

It's my understanding the 3.45 was the standard diff on the manual transmission Camaros with optional ratios available. 3.27 is the standard for automatic cars. No idea on the smaller/larger ring gear fitment, although I would be suprised if you couldn't change the gears in the pumpkin on the OEM diff for our cars. Richmond Gears offers sets if I remember correctly.

We left all bushings stock for right now. The BMR folks want to have a better look at my car so I didn't want to do anything that would alter the base configuration (except replace the diff as a one-for-one swap). All the OEM stuff is in good shape, I just turned 20K miles on the clock.

You have to do a computer tune in order to change the ratios for correct speedo/odometer readings and to retime the shift points for the new gearing. I do still have first gear, but it is somewhat shorter. It's still there however. I suppose first could be programmed off entirely if you played with the tables, but Chris would be more of the information resource on that.

The tune that Chris put in altered a good amount of parameters on the transmission, as well as some tweaking on the factory stock calibrations for the engine. There really is a significant difference on the way the car feels after tuning. The tune Chris installed is more of a split-personality for the car, in normal shift mode it's nice and sort of mellow for my wife to drive. Push that lever into sport mode and..... um.... the beast emerges :) My car will chirp now on at least the 1-2 and 2-3 shifts if I get into it above about 1/2 throttle, we could actually dial some more mods into the tune and see more gains, but for right now we are being somewhat conservative for starters. It was a little wet yesterday with soaking rain and I want a day or 2 of dry pavement so I can really evaluate it well.

(EDIT 1/8/16 - putting the old pics back in this post and a few more that follow...)
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Re: Changing rear ratios

Post by elc32955 »

Here's the rest of the pics... I even resized them from orig. for easier viewing (edited 1/8/16)
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System Manager and your tour guide for the day. 2015 Caprice w/LFX, former NC DPS staff car. Partial hybrid G8/SS/Camaro SS interior mods, SS MyLink radio upgrade, 2016 Camaro V6 rims, GMPP Malibu chrome exhaust tips, otherwise bone stock for now.
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elc32955
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Re: Changing rear ratios

Post by elc32955 »

Here's a pretty good article that speaks to ratio changes, this is specific to the 2010 and up Camaro but it gives specifics on performance gains that should be pretty much be across the board. Anyway, it's worth a read as it discusses the gear swap issue from a performance aspect.

http://thehorsepowerjunkies.com/vehicle ... pin-gears/

NOTE - dead link as of 1/16 and it's not on the Wayback machine... sorry.... Here's another thread where the Camaro guys are discussing 1LE rear swaps to 3.91's.....

http://www.camaro5.com/forums/showthread.php?t=265123

Eric
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Re: Changing rear ratios

Post by Navy Lifer »

So, I suppose this blows your budget for a trip to ISSCA Nationals in Concord next month???
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Re: Changing rear ratios

Post by elc32955 »

Still haven't made my mind up.
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Re: Changing rear ratios

Post by elc32955 »

Welllll...... thought I'd put this post up as a supplement. I've been putting up with noise from the rear end since I did the swap. At first I thought from reading anecdotal tales on the net that the Royal Purple diff. additive was crap, so I had a few ounces of fluid drained from the pumpkin and put a bottle of the GM OEM LSD additive in. No change.

I've been doing some reading recently on other forums and I'm seeing where apparently Royal Purple is not all it's cracked up to be in some diff applications. I'm seeing multiple references to noise after installing it, which is cured ONLY by going back to the GM stock lube and diff additive. Apparently the Auburn diff is noted for this. At this point I'm seriously contemplating doing a drain & fill with the stock GM stuff and see what happens.

Any input/experience anyone can share before I flush Barney down the drain? (well not really down the drain... proper disposal of course. Can't joke too much these days.... lol)

Eric
System Manager and your tour guide for the day. 2015 Caprice w/LFX, former NC DPS staff car. Partial hybrid G8/SS/Camaro SS interior mods, SS MyLink radio upgrade, 2016 Camaro V6 rims, GMPP Malibu chrome exhaust tips, otherwise bone stock for now.
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Re: Changing rear ratios

Post by storm9c1 »

Back in the B-Body days, Royal Purple and the stock (Auburn type) diffs did not get along. It works fine in Eaton diffs, but for the Auburn (and derivatives) you really want to use GM spec fluid, including the friction modifier additive.

Are we sure that the PPV has an Auburn style diff? Seems like GM should be using a better diff than that after all of these years since an Auburn diff is junk IMHO -- it can be smoked by one single burnout or a slip in the snow where one wheel grabs and the other doesn't and you stay on the gas. Ask me how I know (killed 2 B-Body diffs this way)... When they wear, the cone clutch wears into the carrier and cannot be rebuilt (unlike Eaton units with replaceable clutches).

Can you describe the noises? Does it happen on very tight turns, like by driving in a tight circle at 5-10 miles per hour? Should sound like clicking or clunking or even just a groan (caused by improper slip/stick of the clutch due to improper friction modifiers). If so, yep, I'd suspect it's the oil.
Tom (AKA: Storm)
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elc32955
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Re: Changing rear ratios

Post by elc32955 »

Yes to all of the above. Remember this diff came from a 2010 Camaro GT manual (stock 3.45) so it's not the regular PPV diff. The Camaro diff is the bigger unit and the one I have installed currently. Chris Henry has my old diff (2.92), it seems to be exactly the same as the stock G8 GT diff.

Thanks
Eric
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Re: Changing rear ratios

Post by Navy Lifer »

Lubricant type and differential brand & quality has been much-discussed over the years--as Tom alluded to with his personal B-body experience.

Right up front, the PPV owner's manual states:
Rear Axle - Castrol SAF Carbon Modified SAE 75W/85 API GL5 Differential Oil (GM PN 92184900)

Reads like it's pretty special stuff (and not cheap, apparently):
http://www.castrol.com/liveassets/bp_in ... SAF_XA.pdf" onclick="window.open(this.href);return false;

Note comment: (used in) Holden V8 rear axles.

See further discussion here: http://www.g8board.com/forums/showthread.php?t=32799" onclick="window.open(this.href);return false;

Does anyone know what the actual design or brand of differential that is used in these vehicles? The lubricant specified does suggest it may have clutch packs, ala Eaton. I see Auburn (link below) announcing future availability of a Gen 5 Camaro LSD - 218mm = 8.58" ring gear (which I assume may also fit G8, thus PPV), so that suggests what is used in Holden production is NOT Auburn, but remain unsure about the Camaro rear carrier now installed in Eric's car, unless the same Castrol lubricant is specified, which cannot be determined from the posted photos.

The rest of this discussion is not truly pertinent to PPV--Tom gave his 2 cents, and I'm adding my nickel's worth....not to disagree, but to add more perspective.

I'm of the opinion that the Auburn vs Eaton thing got out of hand long ago...each has its devotees and detractors. In the case of the Impala SS, the Auburn got a bad rap for noise, early failure, etc--I don't know how the OE production Auburn LSD used in the mid-90's B-body differed from what they sell in their aftermarket line, but--whether deserved or not--if the Auburn was not abused and if the recommended lube was used, they were reliable and gave good performance overall. The SS was a car that many owners wanted to race--drag, autocross, etc--and I suspect that the LSD unit may have been on the edge based on that, combined with vehicle weight, horsepower (much higher than what had been available even in 1993) and tire size as added factors in the general feeling that the Eaton Posi was superior. Many owners of these cars would change over to synthetic fluids in every system it was available for, behaving like lemmings, really, often because someone on a internet board said that was the hot setup--the manufacturers of these lubricants weren't about to tell the buyers that it was not compatible in some systems, yet that turns out to be the case, at least for the Auburn, and my own recollection about the Eaton was the same--stay with "dino" lubricant.

Besides, the general rule with B-body owners seemed to be that nothing bought at a dealership (aka "stealership") was as good as the aftermarket equivalent, and the quality (sometimes perceived) or price difference (typically lower) for many common items was significant from non-dealer sources, so many, if not most, B-body owners voted with their wallets--GM and other manufacturers have long taken a beating when it comes to this for service items, like lubricants, brake pads, and other common items that are not dealer-exclusive. In the heady days of the mid-90's, the Internet was a place where people with agendas could dominate a board and force their opinion in a board discussion such as the Auburn vs Eaton and diff lubricant questions--there were many fewer folks "connected" online, and fewer who were willing to speak out with a different view or opinion on many topics, this included, so...whether it's true or not, the Auburn was vilified and trashed on a regular basis, and has never really recovered--yet it survives.

If Auburn is as bad as the discussion boards claim, it would have been out of business long ago, it seems to me. The "rebuildable" feature of the (aftermarket) Eaton Posi is something of an anomaly when it gets down to actually recommending & justifying that brand just because it CAN be rebuilt--unless all of the work is done by the owner, by the time the rebuild parts are purchased (good luck readily finding them in some cases), along with the R&R labor PLUS the diff/case rebuild labor, the average owner paying a shop to do the job will instead opt to install a complete new unit.

I would only add here, as a question of correct/compatible lube for the PPV, that the cost of the Castrol fluid will send folks in the direction of looking for a less-pricey alternative, just as happened with the B-body. I think (unless the Camaro owners manual states differently) that Eric has unintentionally come up against a similar situation to what happened with the B-body owners switching to synthetic fluids that were not 100% compatible with some components or systems 15+ years ago, often based on biased and possibly erroneous information. The real question is whether, by not using the recommended lube, this has resulted in the noise problem mentioned, (and whether there are other suitable alternates to the "spec" Castrol lube) or if there may be some other problem with the Camaro rear carrier unit now in his car.

While this has basically nothing to do with what we should use in the PPV rear axle, here are a few links and captured remarks that raise the question of lubricant type to be used in each brand of rear end/differential - I do recall that previous iterations of the current Eaton Posi "install manual" (Eaton link) had a more specific lubricant recommendation than is found in the link(s) below, but other Eaton installation information does suggest to stick with non-synthetics.

Eaton & Auburn links:
http://www.eaton.com/ecm/groups/public/ ... 128310.pdf" onclick="window.open(this.href);return false;

http://www.differentials.com/eaton-posi-faqs" onclick="window.open(this.href);return false;

http://bertok.us/agreif/eaton/eatontech.htm" onclick="window.open(this.href);return false;

http://www.auburngear.com/aftermarket/" onclick="window.open(this.href);return false;

http://www.auburngear.com/aftermarket/d ... esize%3d20" onclick="window.open(this.href);return false;

-IMPORTANT LUBRICANT NOTE
The Auburn Gear limited-slip differential design has been
extensively tested with high quality non-synthetic 80W90
hypoid oils treated with GM or Ford friction additives (3
oz. of additive will treat 1 quart of oil). To avoid differential
clutch chatter (noise) and for optimum performance, use the
oil and additive described above. Use of other additive and
oil types may cause differential clutch chatter.
Ford Part Number: C8A219B546A
GM Part Number: 1052358
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Re: Changing rear ratios

Post by Navy Lifer »

More grist for the mill....just to be clear, I'm not pimp'in for Auburn by posting this information. What I am unable to determine is whether the Camaro & PPV have totally different center sections internally (physically & visually, there are differences, as Eric has shown with his photos) - I cannot find any listings for aftermarket LSD's for G8 (thus PPV), but I may not have looked far enough or in the right places. Naturally, the question is whether the PPV will accept the Auburn or Eaton 218mm units developed for the Gen5 Camaro--someone knows, but I haven't tried to find that answer yet.

When all is done, to build a stout rear end, whether for a PPV or other Zeta chassis, there are some pieces out there that are probably more desirable to have than the stock unit now in PPV. The 2 options addressed here have surfaced, at the very least.

Make note of the gear lube requirements mentioned in the links below.

http://www.auburngear.com/aftermarket/n ... fnews.aspx" onclick="window.open(this.href);return false;

http://www.lsxtv.com/news/new-products/ ... -sema-show" onclick="window.open(this.href);return false;

http://www.lsxtv.com/tech-stories/drive ... camaro-ss/" onclick="window.open(this.href);return false;
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