4L60 or 6L80 when buying used

[redhat]

With some of the recent discussions as of late, got me thinking...

Buying a used GM truck with around or close to 100k on the clock -- unknown transmission service history.

What would you feel more comfortable with: 4L60E or 6L80E, and why? Provided you test-drive the vehicle, shifts good, and trans fluid looks good.

 

[SoNic67]

I don't think it matters for unknown history. The specific abuse of transmission (high temperatures) and neglect (no fluid changes) can render any statistics irrelevant.
4L60E, being longer in service, was revised multiple times (so all the design "surprises" were taken care of in factory) and also has more chances to be correctly rebuilt, because shops are more familiar with it. But even that is not a given.

A bit of history for 4L60E and internals, from a GM transmission repair guru (Richard Crich), that explains that not all the 4L60E are the same:

And a video for 6L80E (where he claims that the TQ is the weak link on those):

 

[KGMtech]

Wonder what Mr. Crich charges to build a 'nice tranny' for the 6L80E in that 2500 truck?

 

[SoNic67]

Don't know, but at least in this case you know what are you paying for. He has lots of videos of rebuilding previously rebuild transmissions and he points out the mistakes or shortcuts that previous shops did in order to "save money".

 

[supton]

I've watched a few of his videos and it's interesting to say the least. No small amount of variations in those 4L60's.

Not sure which I'd feel more comfortable with. The 6L80's should work better (more ratios) but the 4L60 got it done for a long time. I don't know what rebuild cost on either is, but if they are close (and I would guess they probably are by now), I'd probably go by other factors. AFM, miles, rust, options, etc.

 

[CKN]

The 6 speed is solid-as is the Dex 6 that is fill from the factory. I personally have changed Dex 6 at 50,000 miles-25,000 of which were towing miles and it looked real good. So personally-at anything under 100,000 miles I wouldn't worry about what transmission maintenance and what may or may not have been done.

 

[4WD]

Have had both and no issues … have always done pan volume changes … +/-30k …

 

[01rangerxl]

I don't know what the deal is with the 6L80, it seems like early ones were pretty good, but they have some issues in the K2XX trucks. We sell them all the time, and yeah it's a popular truck, but right now for all the dealers that sell wholesale powertrain parts, certain part numbers of the 6L80 are their bread and butter. I bought one on Thursday from a dealer in GA that had 32 of the same part number in stock. I was going to get it in town, but the dealer that had been showing six sold them all before it was approved.

We have trucks at work that have gone 300-400k+ on the original 4L60E, but I'm sure there are 6L80 trucks that have done the same. It's like GM had a bad run of them with the K2XX trucks or something.

 

[01rangerxl]

Have had both and no issues … have always done pan volume changes … +/-30k …

I think an early fluid change is what most "bad" transmissions really need. The 5R44E in my Ranger is supposed to be terrible, but has really been the least problematic part on the truck, probably due to having the fluid changed at 30k.

 

[NH73]

With some of the recent discussions as of late, got me thinking...

Buying a used GM truck with around or close to 100k on the clock -- unknown transmission service history.

What would you feel more comfortable with: 4L60E or 6L80E, and why? Provided you test-drive the vehicle, shifts good, and trans fluid looks good.

Even if you don't know the service history, you mentioned the trans fluid would look good. That says a lot. I have posted this earlier in another post and may useful here.
If the trans fluid looked good and been in there from new, it likely was driven under normal conditions and will be about time for it to be replaced.

 

[CKN]

I don't know what the deal is with the 6L80, it seems like early ones were pretty good, but they have some issues in the K2XX trucks. We sell them all the time, and yeah it's a popular truck, but right now for all the dealers that sell wholesale powertrain parts, certain part numbers of the 6L80 are their bread and butter. I bought one on Thursday from a dealer in GA that had 32 of the same part number in stock. I was going to get it in town, but the dealer that had been showing six sold them all before it was approved.

We have trucks at work that have gone 300-400k+ on the original 4L60E, but I'm sure there are 6L80 trucks that have done the same. It's like GM had a bad run of them with the K2XX trucks or something.

Then you can probably chime in how they are one of the least expensive to rebuild should

Even if you don't know the service history, you mentioned the trans fluid would look good. That says a lot. I have posted this earlier in another post and may useful here.
If the trans fluid looked good and been in there from new, it likely was driven under normal conditions and will be about time for it to be replaced.

I like it how charts get posted by non-owners (I have had three of the transmissions (Silverado/Sierra) in question) over actual OWNER EXPERIENECS.

 

[clinebarger]

4L60E without a doubt, The TCM & Solenoids being one part is a deal breaker for me....6LxxE Torque Converters have a bad habit of coming apart & contaminating the unit so bad it's not rebuildable.

 

[TheLawnRanger]

I have the 4l60e in my Colorado. 155,000 miles so far. I need to do a fluid and filter change.

 

[CKN]

4L60E without a doubt, The TCM & Solenoids being one part is a deal breaker for me....6LxxE Torque Converters have a bad habit of coming apart & contaminating the unit so bad it's not rebuildable.

Really? GM sells over 40,000 units a month of SIlverado/Sierra combined. Most with the 5.3 w/the six speed. Sure there are isolated issues when you sell volume. But there isn't any "bad habit".

Funny I don't see a GM 4 or six speed in your fleet. OR a truck less than 14 years old. I have had three of the six speeds (2011, 2012, 2018)-and none have done what you described.

 

[ripcord]

Clinebarger builds those for a living. Your three examples are a drip in the bucket for him.

 

[clinebarger]

Really? GM sells over 40,000 units a month of SIlverado/Sierra combined. Most with the 5.3 w/the six speed. Sure there are isolated issues when you sell volume. But there isn't any "bad habit".

Funny I don't see a GM 4 or six speed in your fleet. OR a truck less than 14 years old. I have had three of the six speeds (2011, 2012, 2018)-and none have done what you described.

I have a 4L80E in my Camaro....That's a GM 4 speed last I checked And it's getting a built 4L65E soon.

How many miles did you put on your trucks?

I've seen hundreds of TC failures in 6LxxE units & I'm sure transmission builders all over the US have seen similar numbers. Granted....These aren't low mileage units, 160,000-180,000 seems to be the average. As the TC Clutch lining wears....The TCC Piston can make contact with the Converter Cover. As the TCC never really fully locks on a AFM engine.....The speed differential slowly starts making Aluminum debris creating a cascading failure from there.

We should do a pole on miles for untouched-factory 6L80E's??

I drive old beaters because I choose too, Not because I have too.....

 

[CKN]

I have a 4L80E in my Camaro....That's a GM 4 speed last I checked And it's getting a built 4L65E soon.

How many miles did you put on your trucks?

I've seen hundreds of TC failures in 6LxxE units & I'm sure transmission builders all over the US have seen similar numbers. Granted....These aren't low mileage units, 160,000-180,000 seems to be the average. As the TC Clutch lining wears....The TCC Piston can make contact with the Converter Cover. As the TCC never really fully locks on a AFM engine.....The speed differential slowly starts making Aluminum debris creating a cascading failure from there.

We should do a pole on miles for untouched-factory 6L80E's??

I drive old beaters because I choose too, Not because I have too.....

OK-Thank you. High mileage transmissions need repair. Glad we were able to clarify that.

 

[01rangerxl]

Then you can probably chime in how they are one of the least expensive to rebuild should

I have no idea what a transmission shop would charge to rebuild one, but list for a GM SRTA 6L80 reman is typically around $3400. A lot of dealers will sell them for around $3000. It's cheaper than a new truck, and you get a 3 year/100K mile warranty if installed at a dealer.

I know "friend price" for a run of the mill 4L60E rebuild at the transmission shop down the road is about $1600 assuming the core is usable.

OK-Thank you. High mileage transmissions need repair. Glad we were able to clarify that.

There are two vehicles in the shop at work getting GM SRTA 6L80s installed as we speak. One has just under 90K miles, the other just under 115K miles, both are K2XX trucks. I'm sure some of it has to do with greater production volume and more widespread usage of this transmission, but it's more than just a few isolated failures. I'm not saying that every or even most 6L80s will die an early death, but it's not exactly an anomaly when it does happen.

 

[Snoman002]

The folks here have you covered on the reliability aspect.

That said, I much prefer driving my 6L80 (granted, pontiac G8) then my 4L60 (2005 truck). It's not just the G8, to me the additional ratios are a nice balance of not too many, not too few. There is always another gear to drop into if I need just a bit more, but I don't have to keep giving it more and more just to get a big shift and some high rpms for a few seconds. And admittedly, my 4L60 is junk, and so is the truck, so a well tuned unit will feel better. But I stand by my statement and very much like the 6L80, and it sure doesn't seem like a "time bomb"

 

[doublebase]

Really? GM sells over 40,000 units a month of SIlverado/Sierra combined. Most with the 5.3 w/the six speed. Sure there are isolated issues when you sell volume. But there isn't any "bad habit".

Funny I don't see a GM 4 or six speed in your fleet. OR a truck less than 14 years old. I have had three of the six speeds (2011, 2012, 2018)-and none have done what you described.

Well I owned one, and this guy is right. Go to the forums - there are ASE techs over there that have posted threads about the subject, saying that they rebuild the 6-speeds all day long (or I should say replace them) at the dealer. Torque converter shudders, causing the pump to internally fail and dump pieces of metal throughout the entire transmission. Mileage between 80,000-120,000. But there are plenty of people on those forums replacing those torque converters well before that. I believe it’s because of the AFM demanding the transmission to constantly shift and engage the torque converter. Without the AFM and proper maintenance? I think it’s a transmission that will give you useful service for a good 150,000 miles?

I did own a 2018 Silverado with the 6-speed. Never shifted right from day one, and I could have lived with the clunking and constant shifting (in and out of torque converter engagement), but then at 40,000 miles it started shuddering, so I traded it in at 52,000 miles. I took care of this thing too...first tranny fluid change was at 20,000 miles (because I was initially worried about the shift quality), then at 42,000 miles I did a pan drop and filter replacement (because I was worried I’d find metal in there, and I didn’t).

I understand they sell 500,000 of these trucks a year, but that doesn’t change the fact they have issues with the 6-speed. Consumer reports rates the transmission as a trouble spot for these trucks.