cvman

I was considering a LQ-9 but I don't want the 4L80-E. I was wondering if I bought one of these(LQ-9), would the 4L60-E plug into the wiring harness and be compatible?

Xtremes10

I am almost 100% sure they are different from the wiring harness, you could have the wiring harness sent to a company and modified to work for the application tho

P.S. check speartech (www.speartech.com) they should be able to help you out

350SS

iTrader: (38)

To my knowlege, not many 4L80's came behind LQ9s anyways. Many came behind LQ4s. Most LQ9s are going to be from the escalade and silverado ss which many had awd 4L65E's. Regardless, the wiring for the 4L80 compared to the 4L60 is different. There is one additional vss on a 4L80 for the input shaft, but if you go to a 60 you would just leave that unhooked. The main valve body harness I believe has 3 pin differences that you can either change by changing the pins at the pcm or by using an adapter like speartech makes.

'JustDreamin'

I just went through some of this stuff on my conversion.

My harness builder inadvertently set the harness up for a 60E, when I'm actually using an 80E.

Here's the skinny:

The large grey connector on the side of the trans pins out differently for the two transmissions. Pins affected are S, T, and U. On the 80E, locations T & U are not used, but the wire that is in U needs to be relocated to S (TCC lockup). Converting from 80E to 60E may be difficult (you need 2 more wires).

The ISS (Input Shaft) Speed Sensor on the 80E is on the side of the trans above the range selector / neutral safety switch. It requires 2 wires, so if you're going from a 60e to an 80E, you've got to move wires from the grey connector to a new connector for the ISS (and move the PCM end pins as well). Going from a 80E to a 60E will require moving the ISS wires into the grey connector (you'll need pins) and moving the PCM end pins around as well.


So, what it boils down to is the harnesses are different, but not to the point of being completely incompatible.

Also, the programs are different (in the PCM) for the two transmissions.



However, as mentioned above, I can't think of any application where the LQ9 is coupled to an 80E. The Escalades and Denali's all got 65E's. The Silverado SS's got 65's. I'm pretty sure the Silverado HO's got 65's as well (that's the only application I'm not sure of, you'll need to check). I don't know of any other LQ9 applications.

As a general rule, the LQ4's in pickups and vans all get the 80E, because they're only available in 3/4 ton and up. I'm not sure whether LQ4's are available in SUV's other than the 3/4 ton suburban (which I think gets the 80E also).


I hope that helps.....

'JustDreamin'

cvman

Yes, that explains a great deal. Are the 4L65's a good enough trans for a street car?

'JustDreamin'

Depends upon what you're looking to do. Power, weight, build quality, and traction will all affect whether that trans will do what you want or not. The 4L65E is an upgraded version of the 4L60E, which is an electronic version of the 700R4.

I'd suggest you think long and hard about what you want to do.

And lastly, remember, there's a reason that 3/4 ton pickups with the 6.0 get the 80E....GM doesn't like paying for new transmissions any more than we do.....


'JustDreamin'

cvman

This is going in a 56 chevy with 3:73 gears, and will rarely see the dragstrip. Engine probably will be around 400 HP, the 65 should handle that well enough for a street car, right?

76LQ9TA

iTrader: (1)

I am using a 4L80E transmission behind a LQ9 engine. I had the harness for the 4L80E trans and the 4L60E trans and did what was listed earlier. I had the computer reprogrammed for the 4L80E trans. Basically all the programmer has to do is swap the tables from a truck program and modify them for you. I've had to rebuild the 4L60E trans behind my modified LT1. It makes about 380 hp. The LQ9 should make over 400. I paid $800 for the 4L80E and it costs $1600 to rebuild the 4L60E not counting the initial investment. It is a heavier trans and not as efficient. I am fine with this because of the added reliability.

'JustDreamin'

I certainly won't argue the weight issue.

Nor will I argue reliability. At the power levels most of us are looking at, the 700R4 / 4L60 / 4L60E / 65E / 70E is really not enough transmission. Heck, there are aluminum parts in the power path in the 60....

However, I haven't seen any documented proof that the 80E is less efficient. I don't want to argue that point, since like most everybody else, I assume that it is less efficient, since its heavier and built stronger. BUT, when you start modifying the 60E for increased performance, you start pumping up line pressure, which eats horsepower because of increased load on the pump. The 80E may actually use less power at comparable horsepower levels. I would love to see some test data to support either position (less efficient, more, or a wash) so that we know for certain.

I, decided on the 4L80E for my conversion. Having just broken a 4L60E with the stock 195hp V6 (shelled the rear planetary which meant no 2nd, 4th, or Reverse) I wasn't willing to put the same trans in behind nearly twice the power and torque. Just didn't seem to be a wise engineering decision.


As a side note, one of the Syclone guys swapped from a 700R4 to an 80E (with no other changes) and went faster. I expect that some of that change is a result of gear ratios that are more to the truck's liking (less gear in 1st means more load on the turbo & less wheelspin potential). But I certainly wouldn't have expected to add 75lbs (much of it rotational weight) with a less efficient trans and gone faster. Seems a bit counter-intuitive, which is why I'm bringing it up.

'JustDreamin'

76LQ9TA

iTrader: (1)

I would also be interested in some real numbers on the efficiencies between the two. The torque convertor on the 80 is heavier and the rotating parts in the 80 have to weigh more so this is where the efficiency loss comes from. I haven't seen any documented numbers. Reliability, rebuild costs and downtime were more of a concern. The shop owner where I took my 4L60E alos agreed with me; he also put a 4L80E in his car too. The one I bought only had 1400 miles on it. They don't really cost that much more from the junkyard. The programming cost was a wash since I had to have programming done for the cam and vats anyway.

'JustDreamin'

The stock 80E torque convertor is one HEAVY hoss.....Aftermarket ones are a bunch lighter (like half the weight!)

Like I said before, the parts certainly weigh more. They are bigger and have to take a bit more energy to spin up. But an often overlooked factor is the power required by the pump. If you've got the pressures jacked way up, the pump is going to soak up a whole lot more power than the difference between the two rotational inertia's would provide. So, it is possible that the 80E could be more efficient (lower pressure required by the clutches from the pump = less horsepower used) even with bigger heavier parts.


Certainly would be nice to see some un-biased comparisons. Maybe output hp vs rpm at 300, 400, 500, and 600 hp? I'd like to know.....Wonder who would have or be able to provide that kind of data?

'JustDreamin'

cvman

Wat about the 4L65E? How much stronger is it compared to the 4L60E?

'JustDreamin'

Some...The 65E is a revision (some upgrades) of the 60E. The 70E is further revision.....Problem is there are some basic design problems with that trans. Like aluminum in the power path....Aluminum has no fatigue limit, sooner or later it WILL break. Really has no place in a proper transmission. And the shifting method is torture. I can't explain it, except to say some of the shifts are 2 step shifts (stop this then start that) vs the 80E which is clutch to clutch shifting (just turn one on or off)

A number of factors will determine the strength of the trans in your application (usage, power output, traction, build quality, day of the week the trans was built on, etc).

If its comparable money, get the 65 over the 60.

I'd suggest spending some time looking at the transmission forum....Seems like a number of folks are figuring out that the 80E is the logical step up when you're on your 3rd or 4th 60E....And some of us would like to only put one trans in and do it right....

'JustDreamin'