Any helpfut hints for those of us stuck with the dreaded 4L60 suburban tranny?

Rockhounder

Explorer
We on our last trip had to add a couple more tranny oil coolers just to not overheat going up Cajon pass pulling a small travel trailer.
We have the heavy duty (so called) upgrade rebuilt 4L60 tranny and have never liked that at even 1/4 throttle, see that temp gauge climb up.

Any helpful hints, or any direct bolt on swaps for the (what I consider) the weakest link in the drivetrain? We have a total of 3 oil coolers, mounted in front of all other radiators, and also have the oil pane with the 7 quart capacity with the lateral cooling tubes running through.


Aargh!........
 

1stDeuce

Explorer
A well built 4l60 is a great trans, certainly nothing to be afraid of. Sounds like something may not be right though if you're running three coolers and the trans is overheating.

Best thing you can do is use the gear shifter if you're just running it in OD. You need to do some shifting for it when you hit the hills, or it'll try to run a higher gear with the converter unlocked, which builds a lot of heat. Pull it down a gear and let the converter lock up and it'll run a lot cooler. Once you figure out how to feel whether it's locked up or not, you'll find that pulling it down a gear will only add a few hundred rpm if it locks up vs. running the higher gear unlocked. If it still heats up a lot in lower gears, it's also possible that you're not ever getting lockup. That would make a LOT of heat in the hills.

Also, are you still running the fluid through the factory radiator "cooler" too? If so, and if it's after the other coolers, and right before the trans, you're just putting heat back in. It's likely that the radiator is running pretty close to 200F if the ambient is higher (like in summer). If that's the case, take the factory radiator cooler out of the circuit completely and you should see much reduced temps.

And what is "hot" to you?? I've been told a trans will last forever at 150, and anything under 200 is totally fine. By 250 it's getting pretty warm, and it should never go over 275 or so, even towing on a hot day. Where in that range is yours running when you're concerned?

Chris
 

Rockhounder

Explorer
A well built 4l60 is a great trans, certainly nothing to be afraid of. Sounds like something may not be right though if you're running three coolers and the trans is overheating.

Best thing you can do is use the gear shifter if you're just running it in OD. You need to do some shifting for it when you hit the hills, or it'll try to run a higher gear with the converter unlocked, which builds a lot of heat. Pull it down a gear and let the converter lock up and it'll run a lot cooler. Once you figure out how to feel whether it's locked up or not, you'll find that pulling it down a gear will only add a few hundred rpm if it locks up vs. running the higher gear unlocked. If it still heats up a lot in lower gears, it's also possible that you're not ever getting lockup. That would make a LOT of heat in the hills.

Also, are you still running the fluid through the factory radiator "cooler" too? If so, and if it's after the other coolers, and right before the trans, you're just putting heat back in. It's likely that the radiator is running pretty close to 200F if the ambient is higher (like in summer). If that's the case, take the factory radiator cooler out of the circuit completely and you should see much reduced temps.

And what is "hot" to you?? I've been told a trans will last forever at 150, and anything under 200 is totally fine. By 250 it's getting pretty warm, and it should never go over 275 or so, even towing on a hot day. Where in that range is yours running when you're concerned?

Chris

hey Chris,

yes the trans is shifted according to speed. never tow except in D, then when I slow to 45 I shift to 2nd, then go to 1st at about 20 or so. The trans was rebuilt about 3000 miles ago by Aamco in Pasadena.

I took the in-water-radiator cooler out of the circuit completely as I felt that I wanted to keep water temps down a little more.
My bosh electric gauge, mounted in the oil pan reads 150-180 or so normal. When towing, I always pull over and let the temps cool if it hits 210 degrees. When the gauge reads 230 degrees, there is already lots of tranny smoke billowing from under the vehicle through the tranny vent tube (I think)
 

Rockhounder

Explorer
Not trying to be a ********, but that is probably the problem right there. Aamco is horrible. What size trans coolers are you using?

Yeah, but I made sure that the guy who rebuilt it was the guy who used to build 1/4 mile cars, so he at least knows hi perf rules. The trans coolers are two 10 x 14 and one 6x14. (rough size guesses, they are the typical aluminum ones obtainable at local pep boys, etc.) The oil pan cooler has 12 tubes each a half inch in diameter with fins inside, running the length of the pan.
 

Rot Box

Explorer
When the gauge reads 230 degrees, there is already lots of tranny smoke billowing from under the vehicle through the tranny vent tube (I think)

Hate to say it but at that point I'd say the transmission could be 'smoked' altogether.

A couple random thoughts:

Not sure what you have now but from what I've seen the tube and fin style coolers aren't the greatest. A large 'fin and plate' or stacked plate style cooler with electric fan is going to be better than a couple tube/fin coolers imo.

Just hearing the word Aamco makes me disgruntled. That said if you trust the guy that is good.

Freeway flier gears and larger tires can kill an automatic no matter how well you drive it when towing. What is your axle gear ratio and tire size?

How small is your small travel trailer? Any idea on gross/combined weight?

With the picture I've painted in my head I keep thinking you might need something more than a Aamco heavy duty rebuild.


Andrew
 

Shocker

VanDOOM!
That is a non E model right? It should still have the TV cable on it. If I understand correctly, when they are out of adjustment it can cause overheating and other troubles.
 

Rockhounder

Explorer
I have 3.45 axle and am running 33's. Trailer and gear weight is about 4k

I will check if the tv cable is adjusted right
 
I have 3.45 axle and am running 33's. Trailer and gear weight is about 4k

I will check if the tv cable is adjusted right

Do you know how to check and adjust the tv cable? You will need a pressure gauge. See the attached link for a lot of good info. http://www.tvmadeez.com/pressure_test/index.php


Also, if for some reason you ever have to rebuild another trans, check out Bowtie Overdrives. They do great work. I have one and am very happy with it. They are also local to So Cal.
http://www.bowtieoverdrives.com/index.shtml
 

superbuickguy

Explorer
Not trying to be a ********, but that is probably the problem right there. Aamco is horrible. What size trans coolers are you using?

I'll add my voice to this - AAMCO is terrible.

3 coolers? that is a lot of restriction.
- get the largest plate cooler you can, remove the 3
- get a transmission pan with cooling fins
- 210 is starting to get warm, but where are you measuring the heat?

The other way to fix the trans cooling problem is swap gears to 4.10s - your towing mpg won't be affected, but your DD mpg will... in my experience, you'll lose about 2 mpg. Since there are a billion rigs out there with 4.10 gears, you can swap the entire axles pretty inexpensively. When I did so the last time, I looked for a light-duty 3/4 ton (6 lug) axle set - thus I got a bit extra rear beef and it was easier to find the 4.10 gearset.
 

Rot Box

Explorer
I have 3.45 axle and am running 33's. Trailer and gear weight is about 4k

The other way to fix the trans cooling problem is swap gears to 4.10s


Looks like that comes to about ~2250-2350 rpm @ 65mph in fourth gear (1:1). Transmission aside depending on your engine that RPM could put you well under its peak torque at your cruising/towing speed. Imo it's best to stay slightly above your engines peak torque rpm while towing in your 1:1 gear. I'm betting 4.10's (or a smaller tire) would put you in that sweet spot and make the difference here for both engine and transmission. Hope this helps.

Handy little calculator: http://www.alloyusa.com/gear-ratio-calculator/
 

Sooper Camper

Adventurer
i agree, 3 coolers is probably doing more harm than good at this point. find the single biggest cooler you can, it will create less pressure drop (and less failure points!). i honestly wouldn't worry about 210* heat if you are using a good fluid, but the fact that smoke billows out the vent points to something being wrong.

and for what you are doing, pulling the Cajon pass and such, you will be A LOT happier with 4.10 gears. I had an 89 K2500 with 4.10s and a 350, I can't begin to imagine how terrible it would have been with 3.42s trying to tow something, that truck was already slower than molasses on a winter morning.
 

Herbie

Rendezvous Conspirator
Looks like that comes to about ~2250-2350 rpm @ 65mph in fourth gear (1:1). Transmission aside depending on your engine that RPM could put you well under its peak torque at your cruising/towing speed. Imo it's best to stay slightly above your engines peak torque rpm while towing in your 1:1 gear. I'm betting 4.10's (or a smaller tire) would put you in that sweet spot and make the difference here for both engine and transmission. Hope this helps.

Handy little calculator: http://www.alloyusa.com/gear-ratio-calculator/

Another vote for a re-gear. Even in my Astro with the 4L60E (probably ~ same weight as your Suburban, maybe a bit lighter depending on how it's loaded), running with 3.42s and 29.5" tires, I can heat up the transmission on a climb (and the tranny is working VERY hard at that point). The Astro guys usually default to 4.10s for anyone running bigger tires or wheeling, and have generally done fine once a single moderately sized cooler is installed.
 

Larry

Bigassgas Explorer
A NV4500 5 speed manual swap has been known to cure a lot of automatic transmission woes in these old rigs
waytogo.gif
 

Rockhounder

Explorer
A NV4500 5 speed manual swap has been known to cure a lot of automatic transmission woes in these old rigs
waytogo.gif

That actually sounds like the best advice. I have really been interested in this avenue. How much total weight (sub, and any towing weight can it handle, and how about when trying to start from from going uphill, can the clutch handle it? does it mate as is to the engine, mounts, and transfer case?
 

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