4T60-E Auto Trans - Safe HP/Torque Limit?

[3400-95-Modified]

It may even be internal..

Yes its internal, its clipped to the bottom of the valve body.

when the MAF maxes out, i believe the PCM will freak out and refuse to deliver fuel based on the MAF reading, and instead run off of hard-coded default tables...

OBDII will continue to use the last value in the table, which is why sometimes the PE vs TIME table comes in handy, because if you do max out the maf and you know it happens x sec after going WOT then you can use that table to increase fuel delivery by dropping the target A/F

[robertisaar]

OBDII will continue to use the last value in the table, which is why sometimes the PE vs TIME table comes in handy, because if you do max out the maf and you know it happens x sec after going WOT then you can use that table to increase fuel delivery by dropping the target A/F

wow, what a mickey mouse way of fixing something...

[IsaacHayes]

Dude, get a DHP, swap in a 97 Venture PCM, and tune away. Don't band aid it with a FMU. It won't run near as well.

I'm not sure if you can run a 2 bar on OBDII by adjusting the tables (I would think you could, just have less resolution).

MAP measure pressure.

MAF measures amount of air flow.

Sort of like voltage and current...

[AaronGTR]

On the subject of the trans...


The power limit isn't much. 4T60E's are known to be weak. Mine was shot in my '97 grand prix after a little less than 130,000 miles. That was with a stock engine, but a previous owner that didn't take good care of the car.

I knew a guy back in MI with a '95 grand am with the 4T60E who swapped out his 3100 for a 3400. Just that ended up killing his trans. Any kind of HP increase will def warrant a trans rebuild and upgrade. If you are looking at making any kind of serious power I'd even look into changing it out for a 4T65E-HD, or even a manual swap. Depends on your budget.

[pocket-rocket]

To go along with what Aaron is saying, when I got the 91 back in 99 and blew the tranny up in 00 at 99k miles, the one coming out had a "Rebuilt by Hydromatic" sticker on the top. So that tells me that was tranny #2 at 99k. Then I got a used tranny with 110k miles on it for $300 and got 30k miles out of it before it blew. I would trust a 4T60-e behind a stock 3100, or earlier gen (3.1 or 2., but probably not a 3400 and for sure not a DOHC or newer engine without a good heavy duty rebuild like 3400-95-Modified said.

[AaronGTR]

Just gonna add a few more things and answer a few questions that I can.

Even if the air is at 5psi? Won't more air get by then what the pcm was designed to measure due to increased compression, regardless of cooling ability? Or will the compressed air cool the MAF lines faster since it is denser?

Basically, can the MAF see the difference in atmospheric presssures over 5psi boost pressures?

Boost will not affect the MAF. It will still read properly. It does use the IAT sensor to adjust slightly for air density as well as the MAP, but the cooling effect across the wires for different air densities is pretty uniform. Pressure really doesn't affect it. As you said, the cooling increases with the density of the air, so it's really reading the "weight" of the air going in and not the "volume". In fact the MAF table is written in "grams per second" or GMS and not cubic feet per second or anything like that.

Many people have run boosted 3400's with the MAF before the TB and behind the turbo. You just have to put the BOV well before the MAF to keep the reading correct and keep it from making any pressure waves that will mess with the signal. You could also possibly run it with the MAF before the turbo as well, but you'd have to re-route the BOV to in front of the turbo but behind the MAF to recirculate the air instead of venting to atmosphere. The only issue with this setup is I would recommend relocating the IAT to where the MAF is so it is reading the air temp where it is going through the MAF. If you are using an intercooler, then you are not reading the cooler air temp going into the engine and getting the advantage of extra ignition timing. For that reason I would set it up as previously described.

Now, if I max out the MAF, will the symptoms be a leaning condition? Or just an over all loss of high RPM power?

Ok, so I will place the MAF after the BOV. The IAT is obvious where it goes.

Assuming I DO max out the MAF, can I do this...?

Port it out for more airflow (probably a 7%-10% cfm increase). This would lean out the A/F mix since the engine is getting a little more air then it was tuned for. Then increase the fuel mix by pumping up the Fuel Pressure slightly to bring the lean mix back to stoich.

HIGHLY unlikely you will max out the MAF on 6psi. I was running 9psi at 6300rpm before mine went over 10,500Hz. Regardless, the LAST thing you ever want to do is port out a MAF! You won't really be pulling any more air into the engine. The MAF isn't an airflow restriction until higher boost levels. It will however royally screw up the MAF reading and mess up your fueling. Any lean condition would be caused by an inaccurate MAF signal, not more air. The MAF table in the computer is very precisely calibrated for the exact diameter of the opening the wires are in, as well as for the screen in front of them. You never want to mess with that. The only proper way to adjust fueling is by changing the MAF table and other tables in the pcm itself, and if you max out the MAF table you can swap in a MAF from another car and copy it's MAF table into your pcm. I'm running an LS1 MAF in my car right now.

I know it seems like a lot of fuel pressure adjusting, but not too much. I am avoiding tuning the pcm like the plague and the 2 dyno tuners in the area have not returned my emails, 96 OBDII sucks ballz! I feel with a good fuel pressure gauge, wideband O2, Adjustable FPR and a 12:1 FMU with valve bleeder I can get great results w/o pcm tune. I may even utilize a spring loaded check valve that closes at around 3psi, in-line with this check valve will be a valve bleeder. This way I can lean out an over rich mix at mid-boost, a common issue w/ FMU use.

Or just buy the Vortech Super FMU, but they are near $400.00!!! I guess good fuel management is gonna cost $$$ one way or another.

Thanks for the MAF advice!

I hear ya' on that one. There are not a lot of options for tuning GM v6 and most local tuners will not know how to do it. Adding boost to the mix makes it even more complicated. The option is there though, and there are people who can help. It really is the best way to go if you want the best results, but unfortunately it means buying a tuner yourself and learning how to tune. You will have to bear most of the burden. If you really don't want to do that, you can get away without it, but I def wouldn't run more than 5-6psi of boost. You would probably be just fine with either an AFPR or an FMU. I wouldn't do both, and if you get an FMU you won't need a really high rising rate. Anyway, I hope that helps. Best of luck with the build!

[Monzsta]

On the note of 4T60-E durability, I have beat the ever living shit out of mine. I'm talking full throttle launches repeatedly, with my 3700 stall converter, and a few hundred WOT pulls on the highway. Once, before I went to a 180 degree thermostat, I was flogging it home WOT for about 50 miles on a desolate stretch of highway. The converter wasn't locked, and it suddenly lost 4th gear. That scared me good. I put it in 3rd and cruised easy the rest of the way. When I got off the highway, I had 4th gear again, and ever since. It seems the PCM has a temp protection strategy I inadvertently employed wailing down the road on the converter, super heating the fluid. Other than the converter, and some valve springs under the accumulators, it shifts as firm and as nice as when I got it, 40K ago. It has 225,000 on it now and the original owner never replaced or rebuilt it.

I'll also go on a limb here and add a + for tractor fluid in transmissions. I'm running 100% "303" universal tractor fluid and after 15K of hard running you still can barely see it on the dip stick. It's also working in a friend's Yukon's 4l60-e which he tows the living shit out of. I'm going to include it in a Dodge transmission next to see how it runs. It may be a dream lube.

[Schmieder]

Plenty of good advice.

I am noting everything important in my notes log.

Just before my build, I will have all this great info at my finger tips. And then I can make a good set of choices.

Thanks guys.

btw, I have decide to do the PCM swap and tune. I learned a 97 lumina PCM would easily swap into my 96 Grand Prix. I just need to change 3 wires and it's done. Opening my option of HPT along with DHP. AND a better tuning environment!

Now I can put in 36# injectors. A small over kill but I will need them down the road eventually so why not drop them in now is my logic.

[Schmieder]

if you max out the MAF table you can swap in a MAF from another car and copy it's MAF table into your pcm. I'm running an LS1 MAF in my car right now.

That is really good to know. If my MAF ever takes a crap and dies, with the tuner I will be investing in I could easily get a used MAF regardless of vehicle, as long as its GM?

Either way that is a cool trick. I love making things work when they weren't designed to in such instances.

EDIT: To those who say the tranny can't hold under 5-6 psi boost.

I ask this,

The number one killer of automatic transmissions is HEAT. Aside from going way beyond the recommended torque max. In this case it is 280 lb/ft. Over my application. Installing a high quality trans oil cooler will help this.

AND, if I tune the tranny to slip less, less heat is generated increasing life.

So my #1 issue is heat since I am aiming for 250 lb/ft. 30 below the torque limit.

I also learned most manual trans are weaker then most autos. So why should I go manual?

With a B&M Trans Cooler rated at 14.4K BTU, a trans temp gauge, tuning the trans to slip less (more performance), staying below 280 lb/ft and tuning shift points in the torque powerband....why would my trans not hold up?

That is a serious question. It seems the 4t60e can handle 5-6 psi boost pushing 250 lb/ft. And just incase, I'll have a Trans temp gauge mounted to monitor the hot side of the oil.

[AaronGTR]

I would disagree that most manual transmissions are weaker. Most of them are lighter, have better gearing, and have less slip than automatics. Many of them have stronger gears as well and some don't have drive chains and sprockets like autos which is a weak link. Manuals do transmit more shock to the drivetrain which sometimes breaks axles. The advantage of an auto is soft launches and consistent shifting. However with a manual you only have to replace one clutch to make it hold more torque. With an automatic they have a whole set of smaller clutches with far less torque capacity. You can tune the transmission programming and you can cool the fluid, and both of those will help for sure, but there are limits to what they will do. If you keep the power levels reasonable, yes it may still last for quite a while depending on the tranny's rating. With more than stock power though it will wear out faster than normal though and eventually need a rebuild. Running 6-9psi for several years on my 4T45E, the stock clutches ended up worn down and burned up to nothing, and it was slipping on shifts very badly and wouldn't hold any power. The engine was just putting out too much torque for stock clutch plates. Ended up having it rebuilt with raybestos blues.

For now though, yeah I say go ahead and throw a cooler on there use some good trans fluid and see how long it lasts. If you end up upping the power later on and burn it up, you should be able to swap in a 4T65 easily.

[pocket-rocket]

EDIT: To those who say the tranny can't hold under 5-6 psi boost.

I ask this,

The number one killer of automatic transmissions is HEAT. Aside from going way beyond the recommended torque max. In this case it is 280 lb/ft. Over my application. Installing a high quality trans oil cooler will help this.

My LQ1 put out 210 tq stock in the 91. That is not really that close to the 280 tq max on the 4T60-e. Like I also mentioned above, I also had a tube and plate (much better than tube and fin) style tranny cooler on mine rated for a 14k+ lbs vehicle to cool mine. I even went as far as to run B&M Trick Shift in it.

Many many years ago there was a W body owner that went by the name Nico. Nico was no dummy. He had a rare 91 Cutty International with an LQ1/284 (1 of something like 109) I believe. He had also gone through the BMW program at one of the big automotive schools and became a BMW mechanic. He had come across a 284 trans case splitting tool and dismantled his old 284 and had reported back that the gears were only 1 cm smaller in the FWD 284 than the largest gears he has seen in a RWD BMW manual. As with everything in racing though, automatics have their place just like manuals. Don't think I'm a huge automatic hater. I do prefer a manual myself, but that is my driving style.

[Schmieder]

When it comes to fun, I love a manual. I'm with you guys there. And I can drive the **** out of a stick shift.

But I have an Auto for now. I understand manuals have stronger clutches, but only 1 clutch. Where as the auto has many. As long as the auto clutches are in good condition and the slippage is reduced via tuning, it should hold well enough.

It's not like I'm going to pound it everyday. Heck, i drive about 1-5 miles daily. Barely adds up to 365-1825 miles a year. Everything I need is local. Work, school, stores, ect.

Someday, I will drop in a manual. But for now, the auto will have to do. My only concern was how long it will hold up before I drop in the manual.

[IsaacHayes]

Shim the accumulators, you can do that by dropping the pan to get to them. That will make it shift faster and have less wear on the clutches.

[pocket-rocket]

Shim the accumulators, you can do that by dropping the pan to get to them. That will make it shift faster and have less wear on the clutches.

Doesn't that firm up shifts too? Always a good thing in performance apps.