Rear End swap help years compatability

[Alex_M]

Staunchly disagree. 3.73 or more gear would be better for his vehicle, especially for his 4L60E, which is basically a 1/2ton transmission.
So long as he's NOT towing / hauling. Once he's towing / hauling, he better stay out of 4th altogether.What axle gears do YOU have on your Tahoe that gets better MpGs on 35" tires?Just because CAFE MpG tests forced GM into thinking that they could get away with such ridiculously tall gearing does NOT mean that they actually should have - even if they did.
The Caprices RoadMasters & Fleetwoods that had their 4L60Es rebuilt most often were the ones with 2.56.
If he'd asked before doing, NONE would recommend 3.08 over a more appropriate axle gear.
I recommend 4.10 MINIMUM. What was the towing weight rating for 3.23, by the way?

No one said you were trying to be a d-bag.
What does it make me, if after tuning IronBlock LT1s for 11 years, I think that GM should NEVER have offered 2.56 2.73 2.93 or 3.08 in ANY LT1 cars?What Mudsport said, except:
while towing, put it in 3rd AND use Tow / Haul mode SIMULTANEOUSLY until you get tuned - and don't waste any time getting tuned.
Even when not towing / hauling, 4th gear may not save you any MpGs unless you happen to be going downhill.
and
'3.73 or 4.10 to replace the 3.08'.

OP, I sincerely hope your 4L60E doesn't wind up needing a rebuild. On a related note, where's your ATF temp gauge?

Ok, this will be my last response because this doesn't feel like a very constructive conversation. I've agreed repeatedly that a deeper gear would be better, but there is no arguing that a 3.08 rear end isn't servicable because ... they do work, even if not optimal. Anything further is just opinion.

To answer your direct questions -

my Tahoe on 35s has factory 3.73 gears. I don't tow with it much any more, but I have and I would again if I needed to. I would get 12.5-13 on 33s. I am getting 14-14.5 on 35s.

The listed tow rating on the 3.23s is 6,700# with the 5.3 and 5,700# with the 4.8. This is compared to a maximum tow rating of 7,800# and 7,500#, respectively, with 4.10s. A mere 1,100# difference between the two. Assuming that ramp is linear, the tow capacity with 3.08s would be 6,400#, rounded down from 6,449#.

 

[Marky Dissod]

... this doesn't feel like a very constructive conversation ...

We are not the only ones reading this, now, or in the future.
Other people may reconsider their future gearing. Given your thorough answers, they're better equipped to do so.
(Don't understand why this forum doesn't have a 'helpful', in addition to the other six.)

 

[bonester624]

View attachment 405690 I wouldn't be beating on it for the sake of beating on it. I twisted the output shaft off of one. WITH A 4.3 in a blazer.Transgo kits do save a weak design, the only think saving a 4l60e from a 5.3 is the torque management.

I take that back. Won't be beating on it anymore. DAMN. With the 4.3. Did you remove TM on that 4.3? Were did the output shaft snap off? At the front planet?

 

[bonester624]

So, not a good deal, then?

My Z71 already came with 3.73. My soul wilts every time I step on it.

3.90 4.10 or 4.30 will always be better deals than lesser gears.

Still a great deal. Got me back on the road and runnning QUICK. My old diff had 3.73 and my tahoe would take off like a rabbit. No complaints. Then again its an LS 2wd. Your z71 is 4wd a lot heavier.

 

[Mudsport96]

I take that back. Won't be beating on it anymore. DAMN. With the 4.3. Did you remove TM on that 4.3? Were did the output shaft snap off? At the front planet?

1996 4.3 2 years before gm started using TM. And that was just at the sunshell where the shaft gave up the ghost.

 

[bonester624]

1996 4.3 2 years before gm started using TM. And that was just at the sunshell where the shaft gave up the ghost.

Torque management is a 4l60s best friend no doubt. When the 60 in my hoe failed, wasn't a catastrophic failure I just started hearing some gnarly sounds coming from it, like a grinding noise when second gear engaged so I knew it was time to pull it before more damage would occur. Pulled it and sure enough rear planet had damage to the gears, sunshell was on the verge of completely stripping, all bushings were worn to bare metal, all were gm original btw, reaction shaft had tons of play, sun gear had damage too, reverse drum wave plate was eating into drum, besides the usual it still shifted great ocassional flare/slipping into third but was still working good. Surprisingly valve body had no wear at all. Went through all the bores and valves and didn't find anything wrong with it. Oil pump was in good shape, 3 4 clutches were toasty, about it. But yeah gotta keep your ears wide for any unusual noises and know what to look for when breaking one down, and test test test everything before final assembly. Scarf cut sealing rings are great and make things a lot less stressful.

 

[strutaeng]

I'm glad you got your axle swapped on your truck OP. I believe those newer axles are what folks are now calling the "12 bolt". It's really a hybrid axle between the older 14 bolt 9.5" with the axles and I can't recall what else closer to the 10 bolt (bearings?). And 12 bolts on the differential cover, hence the name. Good to know it's a direct swap on SUVs.

I bought one of those to swap into my 99 Silverado. Mine was from a 2014 Silverado and was 3.42. I regeared it to 4.10. But I haven't done the swap yet. I do seem to recall the wms is like an 1" wider. I do know my stock 16" wheels won't clear the newer axle; the rotors are larger. The 12 bolt axle differential portion with the G80 is pretty hefty. I weighed mine and I think it was like 45 lbs IIRC.

My truck currently has 3.42 with a 4L80e. I think 3.73 would be better all around, 4.10 ideal for towing on the upper end.