Rebuilding a modern automatic transmission 1st time?

Hi All. This Transmission is more modern than the 1961 Case-o-matic I rebuilt with generous help from here. Its a 2004 4L60E GM automatic from a buddys 2004 Avalanche. I believe he cooked the 3rd gear components after he pushed it after a cooler line fell off. Its basically a hydraulic unit much like the ones used in some tractors yet more complex than my 1961 Case-o-matic. I consider myself a non-ticketed mechanic of 20+ years. A fellow once told me I could rebuild a modern tranny. He figured it out. Im just not ready to jump into it. I think I could do it. Im skilled enough I believe to fab tools if needed or buy the odd tool if really needed. So does anyone have input? Anyone here able to share their experience jumping into a modern automatic tranny?

Last one I worked on was 1970's Chrysler, with broken parking pall.

No advice on this one.

I do have one bit of advice, I would never do something like this on someone else's car, you will own this for the rest of your life.

Thank you David.

Sorry to be a bummer, just have seen a good deed go punished many times.

I replaced every component in a 10 speed heavy truck Allison. (I was given a new case and rebuilt it from the parts in the original trans. (it
was new with less than a mile on it. Advice: Have two metal top benches end to end. Take images from minute to minute. Clean every bit of dirt
off of it before starting, Clean all reused internal parts to sparkle. Believe all torque specifications. Lube with trans fluid all rubber
seals and orings, Never force anything, Mace sure each component is aligned and don't pound on them to make them line up. Get or make
appropriate tools, don't cobble any tool it will break. Have the torque converter flushed by a machine!!! DO not hurry. Follow directions in
order to the letter. Oh yea, take images. Jim

(quoted from post at 16:55:59 07/03/20) I replaced every component in a 10 speed heavy truck Allison. (I was given a new case and rebuilt it from the parts in the original trans. (it
was new with less than a mile on it. Advice: Have two metal top benches end to end. Take images from minute to minute. Clean every bit of dirt
off of it before starting, Clean all reused internal parts to sparkle. Believe all torque specifications. Lube with trans fluid all rubber
seals and orings, Never force anything, Mace sure each component is aligned and don't pound on them to make them line up. Get or make
appropriate tools, don't cobble any tool it will break. Have the torque converter flushed by a machine!!! DO not hurry. Follow directions in
order to the letter. Oh yea, take images. Jim

Click to expand...

Thanks again David. I hear you. And Jim, thank you for all the details.

These guys have kits with everything you need and the option of a high performance version. Ive seen it done and its not too bad. Highly recommended to just replace the converter.

https://www.monstertransmission.com/4L60E4L70E-Rebuild-Kit_c_5862.html

About 5 years ago the tranny in the wife's caravan crapped out. No 3rd gear. Bought a service manual off ebay and tore it down. Like mentioned earlier just lay out the parts in sequence and take pics, lots of pics. I found a broken hollow splined shaft on one of the planetary carriers. Bought replacements for it and the mating part from a tranny salvage place. Bought a set of gaskets and seals off ebay and put it back together. Measured all the friction plates and metal plates using the specs in the service book. Checked all the bushings and bearings and all were ok. About 5 years and 45k miles later it's still working great. About $300 total including oil and filter for the refill.

There are lots of splines and teeth to be sure are engaged and sliding together. If you feel like you have to force something, back up a step or two. Nothing in it needed to be forced. If it felt tight it was because something was not lined up just right and needed to be twisted or jiggled a bit more to get things started. Once everything is aligned, it all slips together easily.

YOUTUBE video will show you how.

A quality reman trans has ALL new seals and gaskets and ALL new fiber elements. At what point
does your parts costs and time exceed buying a rebuilt unit?
The problem with "fixing it yourself" is that you have to install it into the vehicle to test it. A
reman trans has been tested and has some warranty.
Your skill and special tools notwithstanding, a simple assembly error can be extremely frustating.

Lube fluid for the transmission comes directly from the cooler return line. All bearings and bearing surfaces may be adversely affected. Any interuption of lube potentially destroys those areas.

I've done a few older automatics, but never anything with the electronics.

Not that the electronics would make it any harder, just something else to check. Being an 04 it is probably old enough not to be specifically tied to an ECM, but some of the new stuff is.

I never did enough of them to get comfortable or familiar with the things to look for.

A pro that does them daily will know the critical areas, the clearances that must be right, the areas that give trouble, the areas that don't. He will also know what upgrades are needed and are a worthwhile investment for the application.

But all that depends on finding a good tech, one willing to work with you.

At the time I was doing the ones I did there was no Youtube, no digital camera. I was on my own. But I also had a functioning memory then! I don't think I would be willing to get into one now.

After having a come back with the tranny shop in town, I started doing my own. Don't
skimp. Put a master repair kit in them so you know what you got. You will have to find
a way to compress those clutch pack springs to get down to the seals. Any filings in
the pan & filter gets a new converter. If somebody else figured out how to build it &
make it work, you should be able to take it all apart & get it back together again.
How else are you going to learn?

I must be getting old, you guys are more daring than me.

If man made it, man can fix it. -Nostradamus (probably)

There are people do this for a living. My advise is to
find a good one and hire them. You may even get a
warranty.

Hey all. I really appreciate all the replies. Im pretty sure I wont touch my buddys 4L60E. I have kept an 81 TH350 and 700R4 of my own for rebuilding in the future. Ill try a rebuild on one of those first. I been hunting for a 4L460E and may have just found one tonight that comes from a reputable mechanic. Thanks again for all the info!

FIRST I will double second what David G said, doing your first AT in someone else’s vehicle without a seasoned
trans tech looking over your shoulder every step of the way has a very high probability of causing some friction
between you and the owner.
I have overhauled ATs and here is one caution which repeats what some others have said about being clean.
Wash parts in clean solvent and let them drip off then blow dry with compressed air. Do not wipe anything with a
cloth rag. I remember at one place I worked at a vehicle came in that had just had trans rebuilt at another shop,
don’t remember the why or what for. We pulled the pan off and the filter was a red fur ball from the previous
shops use of red rags. I cannot remember what the issue was because I was not the tech working on it. If you look a
a trans valve body there are probably 25 - 40 spool valves and these new models use aluminum valve bodies.
Very close tolerances, rag lint in those is no good. Sure the filter stopped it but you know there was some
floating around in there downstream of the filter from what they thought was diligent wiping.
A rear wheel drive trans will not be as bad as a front drive as they still use o-rings to seal everything. On the
front wheel drive trans the case sections are sealed with RTV so you have to be sparing with assembly lube so
there is not oil running on the sealing surface while assembling.
Lastly there are no ...over the shoulder.. parts or bolts in an AT. As someone else said you start with a clean
empty bench and if clutch plates are changed or a hard part is replaced have a secondary location to place
anything that comes out in an orderly fashion. When your done the bench is clean and empty so you know
everything is back in where it belongs. If there is any question you have those parts taken out to reference until it
is back in and functioning properly.
Yes you can probably do it. Is taking it on under the circumstances a wise choice in my humble opinion not
really.

Well thats the same transmission that in the older Cadillac and Oldsmobile Aurora, there suppose to be 2,940 parts in them! But there bullet proof if fluid is changed, from what i heard!

Steve, It probably doesn’t matter to this post one way or another since he has decided to swap out the unit. But when you say ... Being an 04 it is probably old enough not to be specifically tied to an ECM... I would like to humbly correct you by saying that transmission is indeed entirely shifted by control of the ECM. In fact I even think that is what the E on the the end of the trans model number designates...electronic shift... Even in the 90’s many automatic transmissions were computer shifted.

This feller makes it look easy.....
Wrench here

I spent about 30 years as a dealership mechanic as my "first career" so to speak. Rebuilding a transmission is about half following directions, another 3/8 common sense, and the rest is so-called tricks of the trade.

First thing to know is that if you have overhauled older transmissions, most of the techniques are still the same.

Second thing is to see some of the similarities between older units and newer ones. The 4L60 is the evolution of the TH350. Basically, they extended the case and fit in an overdrive setup in the front end of it. The back end still has similar components to the 350. The 700R4 was basically the first generation of adding an overdrive speed to a 350. 4L60 and 4L65 are the 700R4 with electronics replacing many of the mechanical controls.

Third thing is not to let the "parts count" intimidate you. When you take a drum apart, you will have a housing, a piston, a couple of seals, a handful of springs, and the retainer and snap ring that holds it all together. For that one simple function, you might be looking at 30 to 40 parts if counted individually. Multiply that b y 3 or 4 drums in some units and it adds up.

As another poster put it, there should not be any parts left over - in MOST cases. There are exceptions. Sometimes there are modifications that call for the elimination of certain parts to improve the function of the unit.

The main things that I have found to be primary causes of failure of 4L60 transmissions:

1) This transmission uses steel check balls in the valve body. Over the course of time, they beat up the separator plate where they seat. At some point, they either punch all the way through or just get stuck in the plate. This interferes with the normal operation of the hydraulics internally, and causes failure. This plate should be replaced at every rebuild.

2) Flimsy and poorly constructed gear train components that fail under pressure. Some components that should have been made of stronger materials were made out of cheaper stampings rather than the forgings or machined castings that they SHOULD have been made from. This caused quite a bit of breakage in some of the units found behind more powerful engines.

The main tools that you need are a spring compressor for disassembling and re-assembling the clutch drums, special tools for replacing the Teflon seal rings on the shafts, and a tool for compressing the springs in the servo.

If you can rebuild a 350, you can do a 4L60.