Towing with a 96-99 Suburban?

[tractoman]

For those towing with these rigs, do you tow in D which will go into overdrive, or do you leave it in 3 to stay out of overdrive. My '98 does not have a tow/haul mode, so even on the freeway in D the rpm's drop under 2k. I've been towing in 3rd to keep the rpm's up and keep the trans fluid pumping faster. Is this the right thing to do? It has a stock tranny cooler in the radiator and an external core in front of the radiator. Mine's a half ton 4x4 with a towing capacity of 5K, and I am close to 4k. Manual says D is OK, but I don't want to kill the tranny.

 

[lime4x4]

Re: Towing with a 96-99 Suburban?

it depends on road conditions. I have 97 3/4 ton sub. I tow around 9000 lbs. When towing on long flat stretches of road i use OD. The 10 minute drive to the local lake i use D

 

[tractoman]

Re: Towing with a 96-99 Suburban?

I wish mine was a 3/4 ton, but I have no OD and D option. I have D with overdrive, and 3,2,1.

 

[lime4x4]

Re: Towing with a 96-99 Suburban?

D is over drive and 3 is third gear. Mine is also marked D for over drive. I use 3 for local trips to the lake

 

[tdrudd87]

Re: Towing with a 96-99 Suburban?

If you are in hills and the tranny is hunting for gears, use 3. If it is stable in D, leave it. It will not hurt anything as long as it isn't shifting up/down constantly. That is when slip occurs and heat builds.

Terry

 

[dockwrecker]

Re: Towing with a 96-99 Suburban?

Nope do not tow in D! Clearly says that in the Owner's manual. 3rd gear is 1:1 and directly coupled. OD is .85:1. You're not going to get any better economy using overdrive vs. 3 and your trans will be much happier.

 

[tdrudd87]

Re: Towing with a 96-99 Suburban?

OP said his manual said to use D.....

Terry

 

[tractoman]

Re: Towing with a 96-99 Suburban?

OP said his manual said to use D.....

Terry

As mentioned, I'm pretty certain the manual says it's OK to tow in D/OD. It is a 4L60E if that makes any difference. We have a couple hundred mile trip each way this summer and it will be through the central valley of CA where the temps are commonly in the 90's.

 

[tdrudd87]

Re: Towing with a 96-99 Suburban?

If I remember the valley, it is flat farmland. I'll stick to what I said earlier, If it hunts, downshift to 3. If it stays in top gear on its own, thats better for the whole system.

If you are concerned, you could install a trans temp gauge. It will tell you the most about how it is working. I have run the numbers on my car comparing engine airflow to calc load, and keeping an eye on system temps, and letting it use 4th when it can is a better situation than making it run at high revs when not needed (in 3).

Terry

 

[bruceb58]

Re: Towing with a 96-99 Suburban?

This post is a good read on this issue. Your tranny may or may not have the newer design.

After all these guesses, do you want to know the real reason why? From a trans tech?.......

First off, the not towing in O/D is limited to certain transmissions and you need to read your owner's manual to see if yours can or cannot tow in O/D. On some Chevy's there is a warning sticker on the driver's door or door jamb area (Mostly up til about '98 or so).

Anyway, back to the real reason. When towing in O/D (we are talking about automatic transmissions only) The engine rpm (which is directly connected to trans pump rpm) is so low that the trans pump cannot pump enough volume through the transcooler to adequately cool the fluid (which is running hotter due to the extra load). So you shift out of O/D to get the engine (and therefore trans pump) rpm up a little higher to allow better flow to the cooler.

The most noted trans that is not recommended to be used in overdrive while towing was the 4l60e used in Chevrolet's. The same trans is still used today, but the no overdrive while towing warning has been removed due to improved transmission pump design.

Even with the old pump design, the only time you really ran into trouble was at slow speeds in overdrive (45-60 mph). If you were towing down the highway at 70 mph the engine rpm was high enough even in overdrive that the trans pump spun fast enough to cool the ATF.

All the heavier duty transmissions used in the 2500/3500 series trucks had no problem whatsoever towing in O/D, by the way. This problem was mostly restricted to light to medium duty trucks and suv's.

Next lesson with be on exactly what the tow/haul switch does, if anybody is interested....lol

 

[JimKW]

Re: Towing with a 96-99 Suburban?

I towed Travel Trailers quite a bit with a 93 Suburban I bought brand new (probably last new car I ever own) and I always towed in D not OD. So now I'm towing my boat with a 98 Envoy which does not have the OD, it has 1, 2, 3 and D. I just assumed that I should be towing in 3rd which is what I have been doing, but after reading this thread I decided to look at the owner's manual and it says to tow in D and that is the best for keeping the transmission cool. It does say if you are getting constant shifting to put in 3rd which to me is just common sense.

 

[642mx]

Re: Towing with a 96-99 Suburban?

Transmissions pump lots of fluid, and they create lots of heat. They create excessive heat when the TC won't stay locked up. The excessive heat is caused by the constant slipping of the torque converter if it won't lock up. Once they lock (and stay there) the TC is no longer slipping and no longer creating excessive heat.

Watch your tach and if you see if jumping up and down a few hundred rpms (without it actually shifting into a different gear) while your towing, then its time to pull it out of OD.

Gear hunting is the first sign of trouble, but its the TC lock up (or lack of locking up) that gets over-looked.... and eats a lot of transmissions.

Thats my 2 cents on this... supported by a degree, a stack of certificates, and years of experience.

 

[45Auto]

Re: Towing with a 96-99 Suburban?

Manual says D is OK, but I don't want to kill the tranny.

You trust some random posters on the internet (whom you have no idea whether their credentials and experience are real or not) more than the manufacturer?

Scan from the owners manual of my 1999 Suburban. If you don't want to follow the manufacturers recommendations, feel free to follow the advice of any random internet poster that makes you happy!

 

[JCMINIS]

Re: Towing with a 96-99 Suburban?

I have a 97,4x4,3.73 axle,5.7. I have roughly 20-25k miles towing my 4200pnd boat in D. No problems, I also mainly tow in the western NC mountains.

192k on the ole burb and still going,well after a new motor a year ago....lol (trans has only had regular oil/filter changes)

Watch for collant leaks !!!

P.S. My owners manual says 6k max tow weight,gearing maby ?

 

[fishingman220]

Re: Towing with a 96-99 Suburban?

i had a 98 1/2 ton with 36in tires and i towed 6200lbs. i would have about a 15mile trip to the ramp, no highway all 45 or 55 mph zones. the very first thing i did when i bought the truck was install a tranny cooler. i have always gotten them from B&M and there only about 50-60 bucks and takes about an hour to install. get the biggest one offered, i think its for a 22-26k lb rating, but its small maybe 8inx11in and goes right infront of your ac condenser

 

[Ganis]

Re: Towing with a 96-99 Suburban?

I have owned many Chevy's over the years and built and rebuilt many of the transmissions in them. You can tow in D, but anything over 2000# and you will only get about 75000 out of with a 700R4 or the later 4L60e. Make sure you change the fluid every 25 to 35K also, and as said above a transmission cooler is your friend. just my .02

 

[BigB9000]

Re: Towing with a 96-99 Suburban?

of course the manual says that!

The EPA is all over them for good fuel economy. Does 3 give the same MPG as OD? No. So tow in OD and get better mileage!

And, Chevy will be selling more transmission parts, and keeping mechanics employed.

I tow 4000 pounds daily on my 4L60E
its called my car! (96 caprice)

That transmission can barley handle moving the car around yet alone a trailer.

 

[mtp9302]

Re: Towing with a 96-99 Suburban?

Mine's a half ton 4x4 with a towing capacity of 5K, and I am close to 4k. Manual says D is OK, but I don't want to kill the tranny.

Hi tractoman, I have a 1999 Suburban K1500 with the 4L60E transmission and 3.73 rear axle. When I first got it I was initially confused about my towing capacity because the bumper has a 5000 lb limit stamped into it, but I had read online it should be 6000 lbs. I actually called Chevrolet and they said that my capacity is 6000 lbs. with the factory options (based on the VIN). The gentleman from Chevrolet said that the 5000 lb limit stamped on the bumper is likely for a bumper tow.

Here are some of the powertrain-related RPO codes that I have; I think 6000 lbs is pretty standard for these trucks, and it's probably safe to count on this number if you have most/all of these options:

C6A ? GVW: 7300 lbs
GT4 ? Rear axle, 3.73 ratio
G80 ? Axle positraction, limited slip
K68 ? 105 Amp generator
L31 ? Cooling system: Trans, HD (I can't find a separate tranny cooler, so maybe this means larger lines to/from the radiator or something like that?)

Not your original question I know, but you might not be as close to your tow limit as you think so it may help a bit.

Also, my boat supposedly weighs 2400 lbs dry, so maybe 3000 - 3500 with fuel and trailer. I've only been doing since April when I bought the boat, but I do tow in D (not L3) and have had good results so far (shifts nicely, no hunting, etc.).