Towing in 3rd gear on a 1300 mile trip
I have a 1997 GMC k1500 Z71 5.7 liter with 20000 miles and a 4L60e transmission with only 2000 miles, I will be towing a 3000# dry weight TT from Louisiana to Colorado. I plan on breaking the trip int...
Forum Discussion
Hi,
I'll give you my experience on the GM's towing and add some to JIMNLIN's good Post.
Before the F350 came to be I am now using for towing, I had the 5.7 in a 98 K1500 Tahoe, then a 2002, K1500 Tahoe and then a 2003 K2500 Suburban all where used in towing with the 2003 K2500 used the most with the TT.
You are absolutely correct, you do not want the hunting in and out of OD like you are talking about. That is a problem and will do harm over the long haul.
When GM changed the engine in the year 2000 upgrades, the new higher revving engine for sure had more get up and go but the OD issue did not get a lot better. If any of mine trucks were hunting in and out of OD, I would shift it down into 3rd and tow.
I found a copy on line from GM of the 97 operators manual and I found what I was looking for. I'm assuming you still have one, if not see here for a down load. https://assets.gm.com/manuals/chevrolet/1997_chevrolet_1500_owners.pdf
Start at page 2-18 where it talks "Automatic Overdrive" and it can be used for towing and if the truck shifts too much, put it in 3rd gear and tow.
Also on that page, it talks about 3rd gear which can be used for normal conditions which offers more power and less fuel economy. Point being, GM does not have an issue driving in 3rd you are just going to use more fuel.
Then go to page 4-56 under trailer towing under "Towing on Grades" where it talks about uphill towing and down shifting to 3rd if the transmission is down shifting on it's own very often.
Now I'll add in a few points. I cannot recall if my 97 had a transmission gage in it. The 2003 K2500 did but that came with the 3/4 ton truck. The 2002 1500 did not have one. You can either put a gage yourself in a hard line under the hood or get a Scan Gage and plug it into the ODBII port. One of these https://www.scangauge.com/products/scangauge-ii/
I had to add one to the F350 as Ford gives you idiot gages with no numbers...
Changing the tranny oil. This is a GM thing. If you look up in the shop manuals, they will not give a mileage recommendation on when to change the oil if you are towing. They say, If towing, change it often.... Point: If you tow a good number of miles each year, change the tranny oil. I had the Suburban setup so I could pump it out of the lines by the Aux cooler and make it easier and quicker. Also the GM's oils temps do run hotter. Some when you get your gage and start seeing 190F or 200F towing in the summer, well that is what they run and the Aux cooler is sized to run at. This is for sure on the 2003 K2500, I did not have a gage on the older 97 tahoe so I do not know what it ran at. But all my TT towing buddies with 2500HD's in the same era truck also ran 190 to 200F. Many are saying your going to burn it up at 200F, but that is what GM sets them up to. Again, reason to change oil yearly.
Now my F350 does run cooler. 160 to 170 but that is a different animal.
Hope this helps and have a good and safe trip.
John
I'll give you my experience on the GM's towing and add some to JIMNLIN's good Post.
Bruce1963 wrote:
My main concern is over heating the tranny, OD is weak in the 4L60e,it has no problem getting to OD but it doesn't maintain the speed in OD, the constant shifting and locking and unlocking the TC is what causes the heat, from what I have read 3rd gear is 1:1 and will actually run cooler in 3rd. I am just new to towing a TT, and looking from tips from those that have experience. I thank everyone for the advice.
JIMNLIN wrote:
3rd gear in the old 700R4 tranny then later in '90 was re'id to the 4L60 and then the 4L60E would be the best gear to tow in.
As others with experience said 4th gear is the OD gear. Even with my 4.10 gears the 5.7 isn't one of the new gen high rpm/high hp engines we have today so it will continually shift up and down with a good size trailer. Use 3rd gear and keep the TC clutch locked.
My 1st one was a '86 5.7 700R4 and put over 180k miles on it with one valve body rebuild.
The 2nd was a 4L60 5.7 I put 235k miles on it with a rebuild at 165k miles. This one pulled doubles for eight years (7600 gvwr 5er and 3400 lb bass boat).
The 3rd was 4L60E had 78k miles and pulled a 10k car hauler flatbed trailer with my blue tractor. No issues.
Good stout tranny for for that era and what its used for if you change fluid/filter once a year and don't abuse it. They don't take abuse very well.
Before the F350 came to be I am now using for towing, I had the 5.7 in a 98 K1500 Tahoe, then a 2002, K1500 Tahoe and then a 2003 K2500 Suburban all where used in towing with the 2003 K2500 used the most with the TT.
You are absolutely correct, you do not want the hunting in and out of OD like you are talking about. That is a problem and will do harm over the long haul.
When GM changed the engine in the year 2000 upgrades, the new higher revving engine for sure had more get up and go but the OD issue did not get a lot better. If any of mine trucks were hunting in and out of OD, I would shift it down into 3rd and tow.
I found a copy on line from GM of the 97 operators manual and I found what I was looking for. I'm assuming you still have one, if not see here for a down load. https://assets.gm.com/manuals/chevrolet/1997_chevrolet_1500_owners.pdf
Start at page 2-18 where it talks "Automatic Overdrive" and it can be used for towing and if the truck shifts too much, put it in 3rd gear and tow.
Also on that page, it talks about 3rd gear which can be used for normal conditions which offers more power and less fuel economy. Point being, GM does not have an issue driving in 3rd you are just going to use more fuel.
Then go to page 4-56 under trailer towing under "Towing on Grades" where it talks about uphill towing and down shifting to 3rd if the transmission is down shifting on it's own very often.
Now I'll add in a few points. I cannot recall if my 97 had a transmission gage in it. The 2003 K2500 did but that came with the 3/4 ton truck. The 2002 1500 did not have one. You can either put a gage yourself in a hard line under the hood or get a Scan Gage and plug it into the ODBII port. One of these https://www.scangauge.com/products/scangauge-ii/
I had to add one to the F350 as Ford gives you idiot gages with no numbers...
Changing the tranny oil. This is a GM thing. If you look up in the shop manuals, they will not give a mileage recommendation on when to change the oil if you are towing. They say, If towing, change it often.... Point: If you tow a good number of miles each year, change the tranny oil. I had the Suburban setup so I could pump it out of the lines by the Aux cooler and make it easier and quicker. Also the GM's oils temps do run hotter. Some when you get your gage and start seeing 190F or 200F towing in the summer, well that is what they run and the Aux cooler is sized to run at. This is for sure on the 2003 K2500, I did not have a gage on the older 97 tahoe so I do not know what it ran at. But all my TT towing buddies with 2500HD's in the same era truck also ran 190 to 200F. Many are saying your going to burn it up at 200F, but that is what GM sets them up to. Again, reason to change oil yearly.
Now my F350 does run cooler. 160 to 170 but that is a different animal.
Hope this helps and have a good and safe trip.
John
