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Inside The 4l60E/4l85E Q&A's



As a Transmission rebuilder and member of CAFCNA, I thought I would share some of the inner workings of the 4l60e and 4l85e transmissions, and some of the common problems I?ve seen with them over the years.
The 4l60e,was introduced in 1993, is an electronic version of the 700r4, which was introduced in 1982. The 4l65E is heavy-duty unit for use behind the 6.0L engines, and was introduced in 2001. Some of the parts were improved to increase its torque capacity. Input and reaction carriers were changed from 4 to 5 pinion gears. An extra clutch was added to the 3-4-clutch pack, hardened input shaft, heavy-duty low roller clutch with wider rollers, and a heavy-duty sun shell and sun gear. All of these parts can be used in the 4l60E. I think they should just use the 4l65E in all applications instead of having two versions of the same transmission. :rolleyes:
The 4l80E has been around since 91 and is basically a turbo 400 with overdrive and electronic controls. A lot of the parts have virtually remained unchanged since 64 when the 400 was introduced. The 4l85E came about in 2002 and has a higher torque capacity. Parts that were improved were the input and reaction carriers, from 4 to 5 pinions gears and an improved overdrive planet and drum. The 4l80E in my opinion is a very strong tranny. It?s had its share problems over the years but currently is the best it?s ever been. One common complaint I see a lot is ?no reverse?. In the 91-96 units I see a lot of direct/rev pistons broken in two. These are made of aluminum. In 97 they went to a metal piston with the rubber seals bonded to the piston. I have yet to see one of these fail yet and use this type when I rebuild them. The reason they break is due to high line pressure in reverse. The reverse boost valve wears out and causes uncontrollable line pressure. I?ve heard of cases where line pressure has exceeded 600 psi, and when this happens you can get some serious parts breakage. I?ve heard of cases splitting in two and have seen myself a direct drum, which is made from cast iron, split apart. Every time I see a unit with a reverse problem it always has a worn out boost valve. The latest 4l80E I?ve worked on was a 2000 with no reverse. I was a little surprised to see this complaint on this late of tranny because I knew it had a bonded rubber piston, which don?t break. Took unit apart and everything looked perfect except the reverse band was burnt, which really hasn?t been a problem with these. Anyway the cause of the problem again was the boost valve. So if there is one thing that I would like to see improved with the 4l80E is that of improving the reverse boost valve. Are there any drawbacks with the 4l80E? Not really, except maybe with the weight of the unit. The torque converters on these things weight nearly 70lbs! I think there is quite a bit a horsepower that is lost driving this unit.
As for the 4l60E not to many changes have been made to the hard parts (planets, drums, gears, etc.) since 82. A larger input sprag and low roller clutch is about all that?s been changed and that was back in 86-87. Once again ?no reverse? is fairly common complaint with these, but for a different reason. I see a ton of broken sun shells. There is a splined area of the shell (splines on to reaction sun gear) that breaks clean off. This area is just not strong enough. So GM has come out with a redesigned shell in the past couple of years to help with this problem, it?s a bit thicker and has more of a radius where the splines meet the base of the shell. Well guess what? Now instead of breaking, the splines are now striping out! I?ve seen this many times on 2000 units, and have heard this from other builders too. I am a little reluctant to get new shell from the dealer because of this current problem. I?ve heard from other builders that new shells they bought and put in have been striping out in as little as 20,000 miles! Not good. :mad: So currently I think the sun shell is the weakest part of the 4l60E. I try to use an aftermarket shell that has hardened splines whenever possible. I haven?t seen what the 4l65 shell look like yet.
There are a few other common problems I see, there is a check ball that likes to wear out the separator plate, and blow thought it eventually. Doesn?t seem to happen to all units. Might depend on how hard it is driven. In the mid 90?s, I saw quite a few bearings in the planetaries fail, usually would cause a lot of damage, but I think that was due to a bad batch bearings.
In the quest for better gas mileage GM has changed the lock up strategy of the torque converter over the years. The original 700 and 93-94 4l60e used an on/off type lockup. Meaning it was off or fully locked on.
In 95 they went to a PWM (pulse width modulated) lockup, which controls the aggressiveness of the apply and release of the torque converter clutch and allows a bit of slippage for a smoother feel.
In 98 GM went to a different strategy called ?Ec3?or electronically controlled capacity clutch.
This strategy has made a big difference in fuel economy by starting the apply of the Tcc at much lower speeds and continually slips until it reaches highway speeds. It begins to apply in 2nd gear and slips up to 250 rpms depending on speed and engine output. In order for this strategy to work a new converter clutch lining had to be developed to withstand the slippage and heat generated. What GM came up with is a woven carbon fiber material that is very porous that allows fluid to flow though it for better heat transfer. This stuff is practically indestructible. One of the problems shops face is getting a replacement converter when doing a rebuild. GM holds a patent on this material. The aftermarket converter companies have been trying to find a suitable replacement material that will hold up. Several companies are very close to releasing their own material. Until then we have only two choices, get a rebuilt converter with a good ?used? woven clutch or buy the converter from the local GM dealer. I personally prefer to go new. I just don?t trust a used lining although this stuff is extremely durable.
The 4l80E uses the PWM type strategy and uses a graphite/ Kevlar composition lining for the Tcc.
The 4l60E PWM units use this material also.
Both the units have been using a High Energy Graphitic lining on the clutch plates and bands for several years now. This material is very durable and can withstand high temperatures. It?s not uncommon to take apart a high mileage unit and find that the clutches look in perfect condition.

One of the areas that I would like to explore further and have some questions about is that of the adaptive learning strategy with both of these transmissions. The adaptive strategy has been in use since 93, but in a basic form compared to what it is today. What is does is it makes adjustments in line pressure to obtain consistent shifts and helps to increases the life of the transmission. As clutch material wears, clutch pack clearances increase, the timing of apply can change resulting in shift overlap. Shift overlap is the time it takes to complete a shift. There are several types of Adaptive learning in use and depends on application what strategies are used. The most common types are, Shift adapts, steady state adapts, and garage shift adapts. Shift adapts are what measure the overlap time between shifts. First the computer must recognize an up shift as adaptable. There are some conditions that can cause an incorrect line pressure adjustment such as the a/c compressor cycling during a shift or a radical change in throttle position, and these types of shifts won?t adapt. When a shift is started a number of things are checked such as throttle position, transmission temp, vehicle speed, and engine rpm, in order if the actual shift time is valid to compare to the calibrated desired shift time. If these items are met during the entire shift the shift is considered adaptable. Once the shift is adaptable the computer compares the actual shift time and the desired shift time and calculates the time between them. This time between the two now becomes shift error. Actual shift time is the time from when the computer commands the shift to the time the engine rpm begins to drop from the commanded shift.
If the actual shift time is longer than desired shift time (slow engagement, soft feel) the computer will adjust the current to the pressure control solenoid to increase the line pressure for the same up shift next time under identical conditions. If the actual time is shorter than desired shift time (quick hard shift) the computer will decrease the line pressure for the same shift under identical conditions.
Steady state adapts is a strategy that allows the computer to make adjustments to line pressure if clutch or band slippage is present. The computer monitors vehicle speed and engine rpm to determine if slippage is present, if there is the current to the pressure control solenoid will be driven down until the slippage stops or sets a code for max adapt. The computer will constantly adjust the current and determine if the slip is still present. If slippage is gone, computer will raise the amperage to the PCS.
Garage shift adapts are for controlling feel when shifting into forward or reverse from park. Shift times are taken from the time it takes for the engine rpm drops from the time the range switch indicates movement from the park position. When the brake is applied line pressure is increased and the time taken will determine for how long it should remain boosted for the proper engagement.
One of the Questions I have is, how will installing a shift-enhancing product affect the shift adaptive strategy of today?s transmissions. If a shift is shortened isn?t the computer going to try and compensate by reducing line pressure? Reducing line pressure during a shift in a performance type application is not a good idea in my opinion. (Just a side note: I?m going to refrain from using the term ?shift kit ?? because it shouldn?t be used as a generic term. It is a regeristed trademark of Transgo along with ?reprogramming kit?? and they don?t like it if it is used to describe someone else?s product.) Is there a way around this Problem? Transgo does make a product that replaces the pressure control solenoid with a vacuum modulator like we use to see on the 350?s and 400?s, to control line pressure. By using vacuum to measure engine load, the computer won?t be able to make adjustments to the PCS, hence more stable line pressure during shifts. I don?t know if it can be disabled thought the computer by reprogramming it or not. Maybe there are some hardcore computer guru?s out there that know a way around it.
I think that some of the shift complaints that some people have posted on different boards might just be that the transmission hasn?t fully adapted yet. When I first bought my Avalanche, it was the first vehicle I?ve owned with the 4l60e, although I build these transmissions all the time I did question some of the shifts for the first few months. I had an occasional harsh 1-2 shift and a clunking 2-3 shift, both have disappeared and now shifts smooth as can be. I think it takes time for the adaptive learning to fully work because not all shifts are adaptable. But if you have a 1-2 shift that is hard all the time, that could be a different story. The first thing is to have it scanned for codes. Some trouble codes will default the transmission to high line pressure, which will give harsh shifts.
One code that has been a big problem with the 4l60e is code 1870 trans component slipping. In 1995 the lockup torque converter went to a PWM type control (pulse width modulated) from the on/off type used on the 700?s and 93/94 4l60e. Two of the valves used, called the tcc regulator and isolator valves wear out the valve body bore because they are constantly moving. This causes excessive converter slippage and sets the code. GM has been working on this problem for several years. I know that when a customer with this problem took their vehicle to the dealer, they would put in a remanufactured service replacement valve body in. These valve bodies had the bore reamed out and a larger valve put in. The only problem is that these larger valves still wear the bore out. In 2000 GM made a change to the separator plate and gaskets to help with this problem. I attended a transmission seminar last year on the 4l60E transmission and was told that GM has issued their final fix for the problem for the 2002 model year vehicles. I guess only time will tell if it is fixed or not. What I do on all 95 and up units is replace the valve assembly with an aftermarket one that has been designed to eliminate 1870. It?s made by a company that produces high quality transmission products that fix the common problems with various transmissions. It works very well and won?t cause any further wear to the valve body.

As for specific problems related to the Avalanche, It?s to early for me to tell. I work for an independent shop and probably won?t see an Avalanche for at least another year, as most people take it to the dealer under warranty. The latest trucks I?ve worked on are 2000?s with high mileage or bought used. I?ve have experienced a few things with my own that others have posted on the different truck forums. Twice I have taken off from a stop and it feels like it starts in second then rapidly shifts 2-1-2-1-2-1. I believe there is a TSB about this. Something about metal shavings in the valve body hanging the shift valve. Since it?s only happened twice and not in the past 6 months, I?m not too concerned about it. I have a feeling if I took it to the dealer, I would get an answer I already know they would say, ?road tested vehicle, can?t duplicate problem?. :mad: Overall I?ve been very happy with the way the 4l60E has worked in my Avalanche. Do I have any plans to do any mods to it? Probably not until the warranty runs out in a few years. As my daily driver, I prefer the smooth shifts. Although I do like firm shifts in performance applications. ;D

Hope this helps with some of the questions about these transmissions. If you have any, feel free to ask, I?ll try to help. :B:

That was one of the best articles I've ever read on transmissions. I don't know where your located but if I ever have transmission problems on my AV I'm sending it your way.
I do have one infrequently occuring problem(about once a month or so) that you might be able to shed some light on.
When excelerating from a stop a little faster than normal the transmission stays in second gear until you let off the gas. I don't know how long it will stay in second if you maintain speed (30-35 mph).
I was thinking it might be the passing gear linkage mis adjusted, but I don't know if these things even have passing gear linkage any more.
Any thoughts?
Mike, I am with bmontini - after reading your fantatstic post, all I can say is DANG, that guy knows a thing or two about the topic. Great info.
Wow . . . excellent article and insight! I'm impressed with the Av's tranny . . . generally seems to do what it should when it should. I'll admit though that the complexity is a bit scary - sure takes more to service today's units than it did in days past.

I guess this is part of why I've always been a fan of manual trannies . . . they're simpler . . . but alas not offered on the Av.

tjcdmc, No they don't have passing gear linkage/throttle valve cable anymore, that was one of the things eliminated when it went electronic.
Diagnosing transmision problems via the net isn't easy, with the computer controlled transmissions today a scan tool is a MUST HAVE item. I like to know if the problem is electrical or mechanical before a transmission is pulled out and gone through, electrical problems can be fixed without pulling it.
In your case I would put a scan tool on it and look at the tps voltage and see if there are any glitches when moving the pedal from idle to full throttle. I would also look to see if 3rd gear is being commanded at the proper time. If it says that it is in 3rd but is still hanging in 2nd I would suspect a mechinacal problem like the valve body. Possibly related to this metal chips tsb problem.

bmontini, I'm starting to get scared with all these complaints of netrualizing, I guess its something I'm going to see fairly soon. :cautious: I guess the way I would go about diagnosing this is put a pressure gauge on it and see what the line pressure is doing when it happens. It seems to me the line pressure may be dropping off enough to not allow the foward clutch to stay engaged then as engine speed increases it reapplies as line pressure increases. But since it happens only once in a while it makes it difficult duplicate and diagnose.
As for the whining problem, does the noise go away when it shifts into second or third? If it does I would suspect a planetary gear problem.
I will see if I can do some of that... but it is tough as it has happened only 2 times in a month or 2...

It almost seems as if the whining is going away some... Do you think it might be something else because it conincides with the engine RPMs? It almost sounded like a bad transfer case, but I don't have a 4WD!!!

Thanks for the insight again...

mike56BA nice post im sure a lot of us will be going back to it from time to time lots of info Thanks. tjcdmc I have the same thing happening to my tranny, its like you wrote that reply for me. Ill keep you posted on what goes on with my tranny
Transmission maintennce(and rear diff maintenance) on the Avy seem to be 2 controversial topics.When do you recommend a fluid change?The manual says 50 or 100K miles depending on service duty.
Do you like GM's Dexron III or going to a synthetic?
Is it OK to remove the drainplug,all the fluid that will come out that way,repeat several times filling with new fluid each time?I know you get only about 3 qts out that way,but doing it 3-4 times will give 90% new fluid.(I'm not sure I want to remove hoses and add fluid with the engine running-though that would get out more old fluid).
Any suggestions??Thanks!
mike, i just bought a transgo shift kit for a 4l80e. im just hoping this will work with the 4l85e. i was looking at the directions and it seems kinda involved. now im not installing the kit myself, im having the dealer do it since i know almost everyone who works there. they have a couple of performance guys down there who are going to do the install. is there anything i should tell them to do during the install? i read the directions and it says what to do if you want a soft, average, or hard shift. what would be the best for this application? thanks

aVOLanche, I Plan on doing the fluid/filter change every 25,000 with dexron III and a bottle of lubegard. I don't know if synthetic is really necessary in a transmission as the temps don't get as high as say in an engine. If you want to change all the fluid, a better way might be to have it flushed. Draining,refilling,running,draining,etc.....will probably not get it completely clean as the fluid will be mixing and you will be draining out some of the fresh fluid you just put in. I'm not to worried about doing a partial fluid change, dexron III is a long life fluid and I'll be changing it 3-4 more times the the manual recommends. If your wondering what Lubegard is you can check it out herehttp://www.lubegard.com/automotive/index.html This is the ONLY additive I would recommend, there are a lot of supplements out there that can do some damage.
Alex, Can't think of anything special to do during install. As far as the shift I would probably go for the hard shift. Soft is what you got now, average is only a slight improvement. Hard is probably what your looking for, although I don't think it will chrip the tires >:D If you do find it to harsh, you can get a replacement seperator plate and drill it for the average shifts. You might check with gandolphxx and see what level he went with. I haven't done too many 4l80e kits and they were more of a shift correction package than a performance kit.

mike, the guy installed the shift kit. im really pissed off because he said it wont go into reverse and it shifts ruff. the guy said he did a 100 shift kits before, i do not believe him. so the truck is at the dealer on a lift and he says he doesn't have time to get to it. the guy who did it is a mechanic at the dealership. so iam out of a truck and he doesn't know whats wrong with it. he thinks theres something wrong with the shift kit, im pretty sure he installed it wrong. any idea what is wrong? i hope he fixes it before i stangle him.

Alex, Is this guy a transmission technician or a general mechanic? unfortunatly a lot of dealers don't have guys that rebuild tranmissions, they just remove and replace with a reman unit. Gee, I've been building for 15 years and don't think I've done a 100 shift kits yet. A couple of things off the top of my head that could cause no reverse are, was the reverse boost valve installed properly, did they use the correct valve body gaskets?, did they do anything with the reverse band servo or leave the cover loose, drill the correct holes, lose or put a vavle body valve reatiner in the wrong place.
Let me know how you make out, If they can't straighten it out maybe we can some how get it up to where I work(Manchester NH)and get it fixed right.
well its over with. my tranny is fried. i do not know what the hell happened. the guy said the tranny fluid was black when he tore it apart again. he took the shift kit out and the whole tranny out. he is overnighting the parts to get it fixed. i called transgo because the guy said the shift kit might be to blame. the guy at transgo said that the shift kit cannot harm the tranny if installed correctly. now im thinking he screwed up installing it. see the avalanche is really my dads truck and i bought the shift kit for it. my dad is pissed. i dout he will want to put the shift kit back in after the tranny is fixed. unless i can covince him that it was the mechanics fault, he will want to send the shift kit back. i don't know what to think.

:C: :8: :cry: Big time bummer........ For the fluid to go black so quick, sounds like it got installed incorrectly.If you haven't returned the kit by sept 28 bring it along with the valve body gaskets he used to the cruise, maybe I can look at it and see what went wrong.
Alex, to be honest with you, its probably not worth it. The 4l85E is durable enough as is. If it was firmer shifts you were looking for, there is another way that doesn't cost anything. The Pressure control solenoid has a torx screw in the center of it visible when the connector is unpluged. Turn it clockwise 1/8 turn, no more, this will increase line pressure about 20lbs. It basically does the same thing as those plug in electronic shift improver modules. Hope everything works out ok.

Just came back from a ride and my tranny did it again :8: ?I had it in T/H mode punched the gas it took off but wouldnt shift. ?It doesnt always happen this is the 5th time. ?It stays in 2nd tack went to 5 grand and I let off. ?Then it down shifted at about 1000 rpms. ?I hope I dont have a problem starting. Mike what is the best thing to do when this happens??This sucks :8: ?AJ
Mike, a truly impressive repository of knowledge! You obviously know your subject exceedingly well! Added to the other people (each of which has some insight to offer about a different aspect of these trucks) you contribute greatly to what is a fantastic resource for owners! Bravo and welcome to the club!

I'm used to driving an old camaro with a built 350/TH350 with wonderful throttle response. When I got the Av and it felt totally dead off the line, I just figured it was the Torque Managment, but now I begin to think that it feels like it's starting in second... hmmm... I'll investigate further. Any ideas?

Crexis do you think that metal filings from the factory install is the problem? I did read about that here.
I have to admit that most of that sounds Chinese to me, but nonetheless an excellent tutorial to say the least...I wish I was that knowledgable regarding trannies....Keep up the good work and great posts... :B:
Does anyone think id have a problem changing my tranny fluid and filter, then if my problem gets to the point were I have to bring it to the General my warranty would be effected or they would hassle me that is was my fault?
Crexis, when you said it felt dead off the line, did you mean when you mash it to the floor or just normal driving? I know mine feels kinda flat when I floor it from a dead stop then really starts to pull when it hits second, which is a little suprising since the 4l60E has the lowest first gear ratio (3.06). But it takes off pretty good if I ease into it. Check out the track times thread in the performace section, somebody else mentions this.
Are you feeling the 1-2 shift? If your first shift is around 15mph, its taking off in first. Have you tried taking off in manual low and see if it feels different?