I HAVE A 2000 GMC 4L60E TRANS.ALL FORWARD GEARS WORK OK AND REVERSE WILL ONLY WORK WHEN I FIRST START IT.WONT GO IN REVERSE AFTER IT WARMS UP?

you need a trans. sorry...

The late shifting could be a control problem but the no reverse is not. These trans had a habit of stripping out the reverse sun shell, the metal from it may have gotten into the valve body causing the late shifting, but it really does not matter. If you have forward movement, but no reverse it has to come out. Sorry dude. You need a trans.

My guess truck wont move in forward gear. if moves when shifts to 1 or low bad forward sprag in trans if under 50000 mi contact GM get customer good will for defective part, This all true if you have a 4l60e or 4l65e trans

Filter should be ok,if this is 4L60E you could have dirty pressure switches pull pan down and look for pieces in pan sounds like reaction drum shell gear broke off.

I have also personally seen/fixed a 4L60E that had a broken reverse servo piston,it is the piece that engages the low/reverse band under a cover in the valve body area,a piston with a band engagement pin. Anyone that has this problem can have it repaired in the vehicle,its worth checking BEFORE replacing the trans unless the fluid is burn't or there are other symptoms present. Good luck and hope this helps. keep me posted, be glad to help

Hi there.This is a common problem with these trans.Its the forward clutches that good bad.First and reverse are together in the same pack The reason it slips when its warmed up is that the fluid is thicker and wont slip by the clutches until it is warmed up.A good way to check this is to look at the dip stick and if it has blackish gray cooler stuff on it it is for sure the clutches.Also if your at a stand still with the truck and in drive if you punch the gas does the rpms race up.The a good indication the the trans is going bad.I hope this helps you and Have A Great Day.

I’m happy to assist further over the phone at https://www.6ya.com/expert/joe_a3369546f8067589

check link to trans to see if is working when you select it to reverse are could be trans pump in the trans may need to rebuild the trans

There isn't a modulator on this trans as it is electronic

You can have first gear going forwrd but no reverse. It is possible. The low/ reverse clutch isn't needed to go forward.

did you do the rebuild or did a shop do it? it sounds like the clutches werernt done properly. if the reverse is out the other gears will go out too if driven too far in that condition,

That is a symptom the transmission has failed.