Still, I think with a conservative throttle foot while towing, there's no reason for immediate concern.
Staunchly disagree. 3.73 or more gear would be better for his vehicle, especially for his 4L60E, which is basically a 1/2ton transmission.
It will be sluggish, but it will get OP around just fine and it will sip on fuel on the highway.
So long as he's NOT towing / hauling. Once he's towing / hauling, he better stay out of 4th altogether.
Hell, my Tahoe gets better fuel mileage on 35s than it got on 33s.
What axle gears do YOU have on your Tahoe that gets better MpGs on 35" tires?
There's thousands of full size GMs running around with 3.08 behind their 4L60Es / 700R4s, & TH350s.
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.
Not optimal, but perfectly serviceable if you're not abusing your vehicle.
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?
Just put it in 3rd manually and use tow / haul mode until you can get a tune.
But personally, I would only leave it in there until you can find another 3.42 or 3.73 to replace the 3.08.
Once you speedo is recalibrate, I'll bet you see a drop in MpG.
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?