• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Transmissions and towing.

charlie31603

charlie31603

New member
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!
2011-02-22_15-11-59_486.jpg
 


the HD is the same thing with worse final drive and a stronger differential.

i dont see the problem other than the blatantly obvious "more load on car, more load on chain, which is already a weak point"
 
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.
 
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.
 


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

That Canadian Guy said:
its the extra power.

more power + more weight = more stress on the chain.
Click to expand...
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.
 
stealthee said:
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.
Click to expand...

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.
 
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+)
 
charlie31603 said:
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.
Click to expand...

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.

charlie31603 said:
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.
Click to expand...

Ahh, it allmakes sense now.
 
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".
 


That Canadian Guy said:
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+)
Click to expand...

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.

stealthee said:
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.
Click to expand...

I'm in Florida. No worries here. lol

That Canadian Guy said:
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".
Click to expand...

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.
 
I belive (but will confirm) that the owners manual says:

Towing capacity 1000lbs (not recommended with supercharged engine).

It might be fine....I wouldn't do it.
 


The major part (concern) when towing with the supercharged engine, is that the possability of running under constant boost will cause the top piston ring to heat up and expand to the point the gap closes and the ends butt together and breaks the top ring land off the piston. This also happens to cars under sustained WOT runs if some sort of cooling the intake charge with an intercooler or alchohol/water injection is not supplemented. Simplest and safest thing to do is open the top ring gap the required amount for the heat/power output of the engine. Although it is a major under taking to perfrom the mod, but is easly accomplished during a rebuild.
IMO, the stock top ring gap is just too tight for a high performance engine with a supercharger.
 
SlowNA06 said:
Keep an eye on transmission temps, and I don't see a problem.
Click to expand...
yea but obviously if your towing I would not be surprised if the temps were 100 degrees hotter don't no for sure tho but In a 3/4 ton chevy if your not towing you can drive all day and the trans temp wont even hit 120 but if your towing its well over 200 obviously theres a diffrence in these vehicals but whats the hottest a 4t65e-hd can get?
 
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.
 
You must log in or register to reply here.
Back
Top