4l60e Help

ArrivalBlueK1500 · January 17, 2011

My parents bought their '96 Blazer LT brand new, and it now has a little over 122,000 miles. On the way home from running errands (one mile from home), Mom heard a thud and the RPMS shot up. She was able to limp it home slowly and got it in the driveway, but when she put it in reverse to straighten it up to pull in the garage, their was no reverse. I got in it, and it feels like it's stuck in 2nd or 3rd, as it is very sluggish when trying to go forward. Reverse would still not engage. after pushing it backward in neutral, we were able to drive it forward and park it in the driveway beside the house. The trans fluid is a very light red, smells unburnt and is full. It was changed probably 25,000 miles ago, probably around 98,000 miles. It had it's first change at just over 50,000. There was no warning prior to this happening. The transmission has always worked flawlessly until now. I am thinking that this is a broken sunshell, but I'm not sure and was hoping to get some feedback. She would like to get it repaired if it isn't going to cost $2,000+ because it still looks and runs great. The 4wd has come in handy with the crazy winter we've had here this year. Any feedback is greatly appreciated. Thanks!

wierdo124 · January 17, 2011

That's strange, and pretty early for a 4L60E to go out. Mine made it to 189k.

Have you tried manually shifting down to first gear? Or else maybe try engaging 4LO, it could be a tcase issue. Usually those are symptoms of a pumpkin failure but it wouldn't act like it's in second or third gear.

DwayneJ · January 17, 2011

Broken sunshell seems likely.

With that mileage you could just repair what is broken BUT you would be taking a big gamble on other problems down the road. IMO a remanufactured tranny or full rebuild is the best course and if paying for the R&R labor you are probably looking at over $2000.

The 4L60E is fickle and the GM tolerances real broad. One will go 200K no problem the next is cooked at 70K.

I am NOT saying they are bad, I have one in a 500hp 4000+lbs street/strip car, I actually like it but the GM tolerances allow for some to be good and some not so good.

ArrivalBlueK1500 · January 22, 2011

Thanks for the replies and advice. I just got done trying out the Blazer in the driveway, but I did not take it out on the road, as I didn't want to do any further damage to the trans. It will go into 2nd gear and move forward when I manually select it on the column. It is also pulling forward with ease in first, however there is still no reverse. I am also hearing a weird sound coming from underneath. It can probably be best described as a whining sound, and it even does it in park. Do you guys have any other ideas? I guess maybe it's not a sunshell afterall if I still have reverse and second. I'd like to know if it still has 4th, but I don't want to mess it up any worse than it is by driving it. Chances are, it wouldn't make it back home and leave me stranded. LOL

oldschool327 · January 22, 2011

check again in 4 Lo. That will help rule out the transfer being the problem. Could be many things at this point.

ArrivalBlueK1500 · January 22, 2011

check again in 4 Lo. That will help rule out the transfer being the problem. Could be many things at this point.

Just went out in the freezing cold and tried 4LO. It engaged instantly with no issues or abnormal noises, except for the whining sound underneath and still no reverse.

Stevens03 · January 22, 2011

As mentioned above, to me, it sounds like the sun shell. Actually pretty common for the 4L60e trans

oldschool327 · January 22, 2011

Sorry to say but looks like you could have two major issues;

Check for 1st gear engine braking by shifting the trans into 1st gear as you are traveling at a reasonable speed in 2nd. Say 15-20 mph downshift to low and you should feel the downshift ,the engine rpm go up, and the truck should decelerate. If if just "freewheels" without any engine braking you have a problem in the low reverse clutch.

The rubbing sounds could be the sun shell rubbing the case. The sun shell tangs get spread out from being driven by the reverse input drum. IF they are spread out the sun shell needs to be replaced. I ALWAYS replace the sun shell with a "Beast" sun shell on a 700 or 4L60E build. It's a $45 part and well worth the peace of mind. It could also be a torrington bearing. Does it increase with the engine rpm or with the gear changes?

The sun shell, no matter what GM design it is, can spread the tangs out that mate to the revers input drum. The common failure if the sun shell is the splines stripping on the sun gear. When this happens you have no 2nd gear, 4th gear, or reverse. Some people don't realize they don't have 2nd, the trans will shift from 1st to 3rd at a late rpm with an odd slide-bump shift. If the sun shell is broken, you will not have 2nd, 4th, and reverse.

1st and 3rd will still function.

Other HIGH fail item that causes that "whirring" noise is when the shaft in the pump gets worn or damaged. Most times it allows slippage in all gears but not always, just makes noise.

There are other smaller items like the magnetic switches on the reverse valve and the rear clutch pack along with the front less likely clutch pack.

I would check the sun shell and clutch with the test I described above, then you will know what is going on or at least verify that you will need to change the tranny or repair it with some buddies and a 12 Pack!

Sly · January 27, 2011

If you go with a rebuild/replacement I would recommend a 2nd gear corvette servo and a billet 4th apply piston and cover.

ChevyTech77 · January 27, 2011

Don't waste the money with the servo's, just twist the line pressure up with the PCS adjuster screw. That will firm up all the gears instead of just 2nd. 1/4 turn maximum.