: new rear end courtsey of gm



2007ThunderV
08-18-11, 09:03 PM
hi there
just recently got a thunder gray cts v and it has the typical rear end howl.
so gm is putting a new rear in next week.
iam looking for some break in suggestions.
i know with my last rear end builds i would go for 100km before lettin her rip?
also iam considering ground force axles once the new rear end is in.
heres a few pics
only mods so far are corsa cat back, k+n panel filer and magnaflow bullit high flow cats
want to do a short throw shifter but dont feel like pullin the tranny

2007ThunderV
08-18-11, 09:15 PM
cant get pics to upload

darkman
08-18-11, 09:18 PM
The break-in procedure that I used on my replacement differential for the first 500 miles is as follows:

1. Avoid constant speeds as much as possible. A long highway trip, for example, is out of the question.

2. Drive in no more 30-minute intervals and allow the differential to cool at least 20 minutes between drives.

3. Brief periods of full throttle are okay, as long as you allow the differentail to cool down soon afterwards.

4. Hard launches, of course, should be avoided.

Change the fluid after the first 500 miles and then again at 1000 miles.

The procedure has worked so far (11k miles on the new unit), but there are no guarantees.

Stepside
08-18-11, 09:19 PM
:coffee: Pictures???? :noidea:

2007ThunderV
08-18-11, 09:25 PM
wow thats quiet the break in

CadzillaTN
08-18-11, 09:40 PM
So the diff should in fact see higher rpms during break in?...
In addition to following the rules above, I've always kept it under 3k but wondered if I should have been harder on it...especially after the times when it seemed to get (much) louder the first time I romped it after that initial period.

2007ThunderV
08-18-11, 09:43 PM
The break-in procedure that I used on my replacement differential for the first 500 miles is as follows:

1. Avoid constant speeds as much as possible. A long highway trip, for example, is out of the question.

2. Drive in no more 30-minute intervals and allow the differential to cool at least 20 minutes between drives.

3. Brief periods of full throttle are okay, as long as you allow the differentail to cool down soon afterwards.

4. Hard launches, of course, should be avoided.

Change the fluid after the first 500 miles and then again at 1000 miles.

The procedure has worked so far (11k miles on the new unit), but there are no guarantees.
is your differantal still quiet?
what do you have for axles

darkman
08-18-11, 09:58 PM
So the diff should in fact see higher rpms during break in?...
In addition to following the rules above, I've always kept it under 3k but wondered if I should have been harder on it...especially after the times when it seemed to get (much) louder the first time I romped it after that initial period.

The only rpms that matter to the differential is driveshaft rpms as measured by mph - engine rpms on the tachometer do not matter. This fact does make the break-in routine a little harder because surrounding traffic often requires the relatively constant speed that should be avoided.


is your differantal still quiet?
what do you have for axles

Yes, my differential is still quiet. I have the DSS 1000HP axles that yield zero wheelhop. I do not launch the car (drag racer style), but I have aftermarket heads (Trickflow 215s) and a cam so wheel spin is a problem in first and second gear.

JDB
08-19-11, 11:14 AM
I did figure eights with it to make sure the limited slip stuff worked itself in, varied speeds and loads, nothing hard, then about 1k later, changed the fluid (GM DEXRON LS gear oil that includes the limited slip)...figure eights again. Gen4 diff, all of this under CPO...on my '05 around upper 20Ks and now about to turn 36k and not a peep.

EdmundGTP
08-19-11, 01:28 PM
I'm surprised nobody addressed this yet, but you don't have to pull the transmission to put in a short throw shifter..

darkman
08-19-11, 01:35 PM
I'm surprised nobody addressed this yet, but you don't have to pull the transmission to put in a short throw shifter..

Nope. The shifter as well as the short throw replacement are external to the transmission. In fact, it can be changed from inside the car albeit with a little more difficulty than from both in and underneath the car.

2007ThunderV
08-19-11, 04:23 PM
Nope. The shifter as well as the short throw replacement are external to the transmission. In fact, it can be changed from inside the car albeit with a little more difficulty than from both in and underneath the car.

really i will have to search a how to on this
def now a short throuw is on the list of mods

darkman
08-19-11, 04:54 PM
really i will have to search a how to on this
def now a short throuw is on the list of mods

Get with PISNUOFF - he is the resident expert (and supplier) of short-throw shifting.

DrSpeed
08-19-11, 06:16 PM
The break-in procedure that I used on my replacement differential for the first 500 miles is as follows:

1. Avoid constant speeds as much as possible. A long highway trip, for example, is out of the question.

2. Drive in no more 30-minute intervals and allow the differential to cool at least 20 minutes between drives.

3. Brief periods of full throttle are okay, as long as you allow the differentail to cool down soon afterwards.

4. Hard launches, of course, should be avoided.

Change the fluid after the first 500 miles and then again at 1000 miles.

The procedure has worked so far (11k miles on the new unit), but there are no guarantees.

What's got me baffled...is that when you buy a NEW car, you would think it comes with a NEW rear end.

No where in the manual does it tell you to change the oil after 500/1000 miles, no long drives, etc.

darkman
08-19-11, 06:52 PM
What's got me baffled...is that when you buy a NEW car, you would think it comes with a NEW rear end.

No where in the manual does it tell you to change the oil after 500/1000 miles, no long drives, etc.

Yeah, the break-in instructions for a new car rarely discuss any details. In my opinion, the most significant omission is the the lack of discussion about heat cycles.

The Cadillac Service Manager that gave me that break-in procedure said it was based largely on his personal observation that a number of CTS units at his dealership had experienced differential noise problems - not just CTS-Vs. He reported that he discovered that more often than not those cars with differential problems had been taken on a long trips almost immediately after purchase. The accelerated fluid change is simply based on the fact that new gears shed metal during wear in and the differential fluid has no filter.

CadzillaTN
08-19-11, 09:54 PM
I did figure eights with it to make sure the limited slip stuff worked itself in, varied speeds and loads, nothing hard, then about 1k later, changed the fluid (GM DEXRON LS gear oil that includes the limited slip)...figure eights again. Gen4 diff, all of this under CPO...on my '05 around upper 20Ks and now about to turn 36k and not a peep.

Figure 8s? Not a peep?

Is this the twilight zone?

2007ThunderV
08-31-11, 05:33 PM
update!
just had my new rear end installed today! wow what a difference, no noise! (yet)
just finished doing a bunch of figure 8's and gonna start takin it for a drive mulitple times a day for short trips on some curbey roads to break it in.
hopefully that will be enough.
once its broken in i will be contacting gforce for one of there axle kits!

CadzillaTN
08-31-11, 07:31 PM
You guys are serious about this figure 8 thing?

Is there another way to accomplish this goal? I've never done a figure 8 in this car. I never even abused rear ends during the waiting period when I knew they would be replaced, so I definitely don't think I could make myself do it now.

My new rear isn't whisper quiet, but it does have the regular low tone whine.. I've only put 300 miles of easy stop and go on it too. As long as it never gets worse I'm fine with it since it's low enough to drown out with sound deadener.

2007ThunderV
08-31-11, 08:31 PM
figure 8's isnt really abusing the car, just gets the c;lutches going, i just put the car in seccond gear at roughlyy 1200 rpm and to the figure 8\s in a parking lot

CadzillaTN
08-31-11, 10:36 PM
Sounds fun but I think I'll just leave it alone unless one of the <300 million people who read this forum but don't post> agree that it's necessary. I would if it were mile 3 but at 300, is the material not already worked in?
I'll be sure to power out of some corners a little harder when I drive it again...maybe that will help.