adventr

Vehicle is a 2009 Hummer H3 with 5.3 LH8 and 4L60e trans. Also has low axle gears, and a 4:1 transfer case.


Having a really weird issue that no one seems to be able to diagnose. About to just completely replace the trans, but thought I'd check here first.



To summarize, I could let just about anyone in the world hop in this vehicle and spend all day driving it, and they would think that the transmission works perfectly.

All shifts are great, torque converter is nice and tight, fluid looks and smells good, never any weird hiccups or shifts, torque converter clutch locks up and holds great....ect.

The ONLY issue that I have with it, is that I can put the shift lever down into manual 1st gear, and the engine doesn't hold you back...

I use this vehicle for camping, and some of the places have some really steep trails. With the transfer case in 4:1, this thing will crawl just about anywhere. However, when descending a steep hill, it's like the transmission is in neutral. Engine stays at idle, and the vehicle just picks up speed.


I tested this out at my loading dock at warehouse. It's a nice steep ramp.

- I can put the vehicle in manual 1st, and it will slowly idle right up the ramp
- Once at top, put trans in reverse, and it slowly idles back down the ramp

Turn vehicle around 180 degrees

- Place vehicle in reverse, and it idles right up the ramp in reverse
- Place vehicle in manual 1st, and it rolls down the ramp just like it's in neutral




So........... Based on that, can anyone tell me what might be wrong with this thing?

I've had some people on another forum (for these vehicles) test their H3s out, and 1st gear IS supposed to hold you back, so I know what mine is doing is not normal.


Thanks in advance!

bbond105

You didn’t say how many miles were on the trans, but it sounds like your overrun clutches for whatever reason are not working. They are the two small clutch disks in the input drum. I am not a 4x4 guy but I would think that the way a 4x4 is used it would be hard on these two clutch disk.

adventr

Ok, so the overrun clutches. Are they only used for decel in 1st gear?

Do you know of any way that I could test/diagnose this any further?

Thanks!!

bbond105

They are only used for engine braking in 1st and 2nd gears and maybe 3rd. I’m not sure about 3th I will have to check my manual when I get home from work. I don’t know of any other way to diagnose this other than put it in those gears and check for engine braking.

adventr

Ok gotcha. I'd say you nailed the problem then. It has no engine braking in 2nd gear either, but it does engine brake in 3rd gear. In 3rd, you can even feel it lock in the torque converter when slowing down.

So in your professional opinion, should I have those clutches replaced in my existing transmission? Or just buy a new 4L60 from GM?

Is there anything that can be done to "beef" those clutches up at all?


Thanks a ton for your help man.

mahone30

iTrader: (3)

summit sells rebuild kits for 4l80e, which im looking into, so id imagine they offer similar items for 4l60e, may be worth while to take a look on summit

bbond105

Yeah. The trans will have to be taken apart to have the clutches replaced. At that point depending on how many miles are on the trans you may want to have the whole thing rebuilt. The choice is yours. Have you looked at some of the sponsors on this forum? FLT, PerformaBuilt and others can build a trans to meet your needs and may be better than a GM unit for close to the same price.

Most everyone on this forum builds transmissions for drag racing so upgrading the overrun clutches is not needed; this would be a 4x4 thing. I’m sure it can and has been done, I just haven’t heard of anyone doing it. One of the sponsors I’m sure will know how to do this, give them a call.

adventr

Ok cool. The vehicle has almost 80k on it, but has honestly been pretty pampered its whole life.

I'll look into some different options. Was just leaning towards the GM replacement for this rig since it's kind of a daily driver/camping vehicle. The 3yr warranty and sub $2k price makes it pretty tempting. LOL

mrvedit

I agree with bbond105 that the overrun clutches are not engaging. The trans engages them when the shifter in in [D1] and [D2] and also in 3rd gear in [D3]. (They are not applied in 1st and 2nd gear in [D3] despite what the ATSG manual says.)
The hydraulics of the trans controls this, not the PCM.

You say that you have engine braking in 3rd gear in [D3], but not in [D2] or [D1]; that is strange as it would indicate the clutches are functional and the valve body has a problem. I would expect the 2x clutch frictions simply to wear out. If you have a local trans shop rebuild the trans they should test this carefully so that they will know what to double-check during disassembly.

adventr

Hmmm, Interesting. So you're saying that if the overrun clutches are worn out, that I wouldn't have engine braking in 3rd gear?

I checked for that the other day. Was cruising down the road at 55mph in overdrive. I let completely off the throttle, and then manually moved the shifter down to 3rd gear. The transmission downshifted, and the engine rpm increased as one would expect. After a second or two, I even felt the torque converter lock back up. This resulted in nice engine braking.

Once speed was down around 25mph, I manually moved the shifter down into 2nd gear. I felt the transmission actually downshift, but then it was like I put it into neutral. Then engine rpm dropped to idle, and it just coasted along. Same thing occurs when dropping it into 1st gear.
Another thing to note, is that when its freewheeling in 1st or 2nd gear, there is a noticeable gear whirring noise that comes from the trans area. Kind of sounds like an electric powered RC toy car, when you accelerate hard and then let off and it coasts. Does that make sense?


I've not owned this vehicle very long, but I do know that it had never been Offroad before. I almost have a hard time believing that the clutches are burned out... Lol

z28camaro82z

the hub driving the over run clutches may be broken. sometimes the teeth can be sheared off. most commonly when you live in a mountainous terrain. another possibilty is a hyperextended over run piston seal. Either or, the over run clutch is unable to engage.