I have a 2wd 01 Silverado with a 4L60. Today I started hearing a loud roaring noise when it is in high gear. If I accelerate and it drops to 3rd gear the noise immediately stops. If I drive it in tow/haul mode essentially taking overdrive out of the equation it never makes the noise. I did notice it shifting harder from first to second the last couple of days. Should I start looking for a transmission or do you guys think this one can be saved?

 

4th gear runs through the rear planet set and it's probably spit a needle bearing out. Sounds like it's time for a rebuild. Anything can be fixed it's just a matter of how much hard part damage is done. I personally would stop driving it. Do a pan inspection and see what it looks like inside... Plan on a rebuild or a replacement.

 

You mentioning both 4th gear and 2nd gear indicates a likely problem with the band. Possibly it is slipping; the noise could be from a very rough and worn drum under the band.
An '01 trans can be rebuilt, which is a safer bet than buying some random trans. Anything you buy or rebuild under $1200 will be garbage.

EDIT: I see that Tranzman just posted at the same time as me. Since he is much more experienced, his noise diagnosis is likely correct. The 3/4 clutch and the band are weak spots that typically wear out with mileage. I would still go for a rebuild.

 

Agreed probably rear planet issue time for a trans or Rebuild
I can set you up with this for $2600.00 shipped take a week or two to have ready
Performance / HD build.
1- NEW FRICTIONS
2- WIDE RAYBESTOS PRO SERIES 2-4 BAND ON NEW REVERSE INPUT DRUM
3- 9 FRICTION 3-4 SET SPECIALLY MODDED TO TAKE THE HEAT. (The steels are relieved to trap oil to aid in cooling during apply, The frictions are carbon composite)
4- BEAST SUNSHELL
5-CORVETTE 2ND SERVO
6- SONNAX DUAL PISTON 4TH SERVO
7-BORG WARNER HEAVY DUTY DUAL CAGE SPRAG WITH IMPROVED OILING
8-BUSHINGS DUAL IN CRITICAL AREAS
9-TRANSGO BOOST VALLVE .500
10-MODIFIED PWM CIRCUIT FOR CONVERTER CLUTCH LOCKUP - FIRMS APPLY.
11- CUSTOM 3-4 SHIFT VALVE SPEEDS 2-3 SHIFT DRAMATICALLY FROM COMMAND TO APPLY (custom not sonnax).
12- Valve body mods to keep overrun clutch on even in OD position while in 1-2-3 gears this supports input sprag for launch, kickdowns , towing, pulling. Roll racing (custom mod you will notice and feel the 3-2 downshift coming to a stop) and new valve body plate
13-Sonnax pinless accumulators.
14 -Custom shift kit gives progressive shifts as throttle increases not banging all the time like some. (This is Important as the really harsh banging destroys hard parts it takes a balance) 15-New wiring harness and shift solenoids. 16-New heavy duty deep pan with drain plug that actually can be removed!
17- Case is cleaned then soda blasted (no sand or nut that can become embedded in casting or feed holes to cause issues - soda dissolves in water at second wash Then painted with VHT HIGH TEMP ENAMEL which is then baked on to 180f for long lasting protective finish.
18- Comes with long linkage shaft this can be used in any application if your original was short just turn linkage lever around. .
More Is done than listed even. But this is the overall build.

$2600 to your door no core required, Take about 2 weeks or less to get ready. More options can be added on request.

Sorry for the gray type I copied pasted from my website I am working on. Ah I fixed it.

Frank