2007 Suburban Z71 towing question

[Jpedigo]

Hey guys
I'm new to towing a camper. We have a 24' tt dry weight 4500#. I just found out we have the gt4 (3.73) gear ratio on our tv.
We have put a transmission cooler on the vehicle to cool it down but it still runs over 250 on the interstate. On our last trip I got a little more comfortable with towing the camper and I got up to 70 mph. After about 15 miles the transmission warning came on.
I was wondering if anyone might know of anything else I might try. We have looked at 3/4 ton trucks but we cannot find one that fits our needs and budget. Lol
I thought about replacing the rear gears with the 4.10 but didn't know if that would create a whole new set of problems.
Any suggestions would be greatly appreciated.

[Jpedigo]

Thanks. I will have to get that checked.

[Turtle_n_Peeps]

You have a mechanical problem.

I don't care what gear you have it in; whether you have it in OD or not; whether your fan is working or not............something is seriously wrong with your cooling stack or transmission.

No way, no how should a tranny get that hot on a flat road towing that load at that speed.

At 65 or 70 MPH on a flat road you don't even need a fan.

Don't let anybody on this forum tell you that your driving your TV wrong. You need to get your TV to a trusted mechanic that knows what they are doing with transmission cooling problems.

[Grit_dog]

Jpedigo wrote:
I think I need to just slow down. I normally drive between 58 and 65 so I am probably working that tc. I did read the owners manual and it said I can tow in 3rd. I may try that to see if it lowers the transmission temp.

There's no may about it. If you were dogging it in 4th/OD then it ran considerably hotter than if you were in 3rd with enough power to keep the converter from unlocking.
I think you'll be fine with your setup although additional fluid capacity and cooling will help a bunch as well. Have to remember the limits of what yer driving. You're not going to be able to keep up with the HD/diesel crowd with a 10 year old half ton.
Good luck, btw always like the Z71 models. They're cool!

[Jpedigo]

I think I need to just slow down. I normally drive between 58 and 65 so I am probably working that tc. I did read the owners manual and it said I can tow in 3rd. I may try that to see if it lowers the transmission temp.

[jsteih]

GWolfe wrote:
The tow/haul will not take it out of overdrive if you have the 4 speed transmission, you will have to put the gear selector in 3rd yourself. At least my 04 was that way.

This is wrong. If you are running tow/haul mode on a 4L60E, it will hold third gear locked up until you get over 63MPH. Then it will shift to 4th with the TC locked, if you increase RPM enough to unlock the TC it will automatically shift to 3rd gear.

[Grit_dog]

Ya try towing again and make sure it's locked in drive/3rd gear and check the temp.
Letting the engine wind up is better than bogging the trans and final drive ratio down.
It won't be first up the hills but no reason that rig shouldn't to be able to tow 6klbs in the flats without issue.

Other not horrendously expensive mods if still running too warm and you don't have another obvious issue is deep trans pan with cooling fins, second trans cooler if you can get it plumbed in somewhere.

[Jpedigo]

Well I am definitely learning some things I didn't know.

[APT]

Tow/haul trans mode and lock out 4th/OD when towing any high walled RV. You'll want to spend all your time >2000rpm, closer to 2500/3000 is better. You'll actually have better throttle response, lower trans temps, and likely use less fuel.

[Terryallan]

Thing is. Running in a lower gear (5th or 4th. This will turn more RPM causing the fluid to flow more, and so keep it cooler.

And BTW. Your tires are only rated for 65 MPH

[GWolfe]

The tow/haul will not take it out of overdrive if you have the 4 speed transmission, you will have to put the gear selector in 3rd yourself. At least my 04 was that way.

[Jpedigo]

I do use the tow button to take it out of od. And I really appreciate all of the input. 🙂

[BenK]

Jpedigo wrote:
Hey guys
I'm new to towing a camper. We have a 24' tt dry weight 4500#. I just found out we have the gt4 (3.73) gear ratio on our tv.

Going to a higher numeric diff ratio (two if 4x4) will increase the
power (torque) to the pavement...therefore higher MTWR (Max Tow
Weight Rating) of the TV

With the new platform and the close ratio automatic has 0.6:1 double
OD

We have put a transmission cooler on the vehicle to cool it down but it still runs over 250 on the interstate. On our last trip I got a little more comfortable with towing the camper and I got up to 70 mph. After about 15 miles the transmission warning came on.

Says either or both you are at or over the ratings of your TV...or that
the heat management system is marginal or going south...

I was wondering if anyone might know of anything else I might try. We have looked at 3/4 ton trucks but we cannot find one that fits our needs and budget. Lol

Yup...next higher class TV would help or solve

I thought about replacing the rear gears with the 4.10 but didn't know if that would create a whole new set of problems.
Any suggestions would be greatly appreciated.

Yes, re-engineering anything needs to have the engineering reviewed
for the new thing(s)

Note that the various "highly integrated' computerized vehicles will
need to be potentially re-programed...

[Campfire_Time]

Even so, from a purely mechanical standpoint you should be able to tow at 70 and not hit temps that high. That's a 4 speed transmission, make sure you have it in 3rd when towing so that it doesn't downshift unnecessarily. Lots of shifting drives trans temps up.

[Jpedigo]

Thank you. Yep...the warning didn't come up until I was driving 70. I won't be doing that anymore.