Thread: Transmissions and towing.

So why can you not tow with a 4T65E-HD? I know the owners manual says not to tow with the GTP. Doesn't say why. I thought it was because of the suspension. But my friend told me I shouldn't tow anything when he saw the picture of the Minivan hooked up to a medium size lawn trailer. I said why. The minivan has a 2000 or 3000(towing package) pound tow capacity. He said it had to do with the transmission from the GTP. He said the manual said no towing. And something about the gears. It just doesn't make sense to me. That both the minivan and the other Grand Prix's can all tow with the weaker transmission. But the "HD" can't handle the extra load. So my question is, why? even though I swapped the L67 and the 4T65E-HD transmission in the minivan that has a chassis that can tow at least 2000 pounds. And yet I can't? Why? It seemed to tow just fine with that trailer on it. And it was in between 1000 and 1500 pounds. So if anyone has any insight. Please let me know. Thanks in advance for all the help! Adam :-)

Get'r'done!

But wouldn't the load on the chain be the same in both the HD and non HD trans? And I still don't see what gear ratio has to do with the strength of the trans. Yes it might not pick up and go as it would with the 3:29 gears. But I don't see how the 2:93 gears are weaker.

if i were to ever tow something with the prix, i would never let it go into fouth gear.

You keep saying chain. I beleive the OP is talking about using a hitch receiver.

And power really has nothing to do with stress on the chain if you know how to tow with a chain.

Originally Posted by Fivefingerdeathpunch

if i were to ever tow something with the prix, i would never let it go into fouth gear.

That just makes no sense to me at all. I figured 1st or 2nd gear when taking off and accelerating would be the worst. 4th is just cruising.

Originally Posted by That Canadian Guy

its the extra power.

more power + more weight = more stress on the chain.

I can see that if I full boost it while towing. But not as much if you take it easy like you should be towing a trailer.

Originally Posted by stealthee

You keep saying chain. I beleive the OP is talking about using a hitch receiver.

And power really has nothing to do with stress on the chain if you know how to tow with a chain.

Talking about the chain(gear ratio) inside the transmission. And how it is weak and will brake if used to tow.

The hitch part I have taken care of. And I use a trailer. But I do know how to tow with a chain if need be.

Originally Posted by charlie31603

That just makes no sense to me at all. I figured 1st or 2nd gear when taking off and accelerating would be the worst. 4th is just cruising.


I can see that if I full boost it while towing. But not as much if you take it easy like you should be towing a trailer.

You want to keep it out of overdrive when towing as much as possible. You will actually get better fuel mileage keeping it in 3rd than having it constantly kick in and out of OD. Its also not good for the trans to keep kicking in and out of OD.

The only way I ever use OD when towing with anything is if I am on a long straight flat stretch. Thats not too often I can do that around here though.

Originally Posted by charlie31603

Talking about the chain(gear ratio) inside the transmission. And how it is weak and will brake if used to tow.

The hitch part I have taken care of. And I use a trailer. But I do know how to tow with a chain if need be.

Ahh, it allmakes sense now.

Originally Posted by That Canadian Guy

if your transmission isn't an 03+ then the fourth gear hub doesnt have hardened splines.

keep it out of fourth when towing.

IMO keep it out of fourth unless you're cruising at high speeds. (50+)

The trans was swapped right before I bought the GTP. My friend bought it from Morad. Need to ask what year it is. I know it was atleast a 2000+. Car was a 98.

Originally Posted by stealthee

You want to keep it out of overdrive when towing as much as possible. You will actually get better fuel mileage keeping it in 3rd than having it constantly kick in and out of OD. Its also not good for the trans to keep kicking in and out of OD.

The only way I ever use OD when towing with anything is if I am on a long straight flat stretch. Thats not too often I can do that around here though.

I'm in Florida. No worries here. lol

Originally Posted by That Canadian Guy

Overdrive or lockup?

These transmissions don't have an "overdrive" box like you'd traditionally use.

Fourth gear is "overdrive". Fourth is weak, but keeping it out of lockup will require a "button" that tells the PCM to use a different tranny table.

Basically performance shift but have it set up as "towing mode".

Now I did wire in the performance shift button to a non used TCS switch. So I do have that option. Right no it has stock trans settings when off. And some tweaked settings when on. Friend tuned it. 6200rpm shift, firmer shifts and no lock up till about 45ish mph.

Originally Posted by mechguy

It seems quite possible that the supercharger could overheat when towing. So don't.

How?

There's some pretty cool guesses as to why not to do it. The skinny of it is..you "can" tow with it.

Keep in mind the torque that the charger makes and when there's a load on the car...you'll have boost happening when you are towing. That can load things up and cause more stress. Keep the trailer as light as possible for the stress on not only the drivetrain..but the braking as well.