automatic transmission shifting procedure

[Timeking]

Just checking my methodology to see if "all" agrees. I am towing a 5000 lb TT with a 2006 Chevy Trailblazer with the 5.3 vortex v8. I tow in 3rd. When going up a steep hill, I wait until the computer decides to go into 2nd, then pull the lever down to 2nd so it stays there until I get to the top of the hill. Max speed in 2nd is 45 mph, ~3500 rpm. On a few occasions (like getting up onto Skyline Drive from Orange VA) I've had to go all the way down into 1st and crawl to the top, keeping an eye on tranny temps as I go. So what is the best way to go into 1st? I've got a Scanguage and can see the engine "load", and it worries me when the engine is pumping out 95% of available power, and then downshifting to first with that much torque might break something. I've had both my motor mounts replaced, though I don't know whether the guy that owned this vehicle previously did that, or whether it was me. I've towed this trailer some 40,000 miles. I am thinking that I should let the vehicle slow down to 30 mph, and then jam it into 1st, rather than let the computer make that decision. The risk is that if I let the rpm's get too low in first, then I could slowly slow down to a stop ... and that would suck, not only for me, but for everyone that is behind me!!! Do I trust the computer, or trust me brain?

I am heading to the Arches/Glen Canyon NP area next week.....

[sleepgsr]

PUCampin wrote:


This is part of the problem. Modern small block Overhead Cam V8s DO NOT have a ton of low end torque, most torque and power is made by spinning the motor.

Ummm, Chevy's 5.3 is a cam in block pushrod, not overhead cam. But your right, its power band is between 3500 and 5000 rpm

[Timeking]

Chevy had a lot of problems with the 4L60E prior to 2005, so likely reason the tranny died. 3200 rpm in 3rd gear for me is 68-70 mph ... don't think I will manually shift down to 2nd going 70! Throw in a few 15mph hairpins and you're airborne. I think I'll just keep doing what I have been doing, which is

1) if I am losing it in 3rd, and it goes to 2nd, I'll manually keep it there until I feel its time to go back to 3rd (avoid hunting)

2. if I feel I am losing it in 2nd, and it goes into 1st, I'll do the same.

From some of the replies to my original post, it would seem that ?some? don't have gasoline V8's trying to pull a heavy load when going fast (high rpms) is out of the question. When I finally blow this thing up, I'll likely get a diesel, until then happy trails to me.

PS: I get passed all the time by guys going 70, but then I often see them changing their tires after a blowout. Fun. Many of these crapppy Chinese trailer tires are only rated at 60 mph. You should check if you don't know. Just friendly advice.

[Hybridhunter]

I suspect that the OP needs to push the accelerator to the floor, and just let it do it's think.
OP - You are likely better off in 2nd, revving higher, and maintaining some speed, than getting bogged down by trying to baby it. My dad used to do this when he was new to towing. It seemed like brutal abuse to the truck, now he just pushes the pedal to the floor, and the engine rev's like it was designed, and goes.

[Bipeflier]

Expect the tranny to go "byebye" at about 140-160k miles in these. Our family has had 3 of the 03's and serviced by the book. Almost like the old alternators of the late '80's, like clock work.

[mbopp]

I would lock my Envoy in 2nd gear and let it wind to 4000RPM going up a hill. I'd lock it in 1st for steeper hills.
With the F150 I hit the Tow-Haul button and let the computer decide.

[Timeking]

PS: I drop the pan and change the tranny filter every 30K.

[Timeking]

As far as my transmission needing checking, I've towed this TT for over 40,000 miles now, so I'd think if it was going to die, it would have long ago given up the ghost.

I am glad I posted because PUCampin seems to know his stuff and I think the "drop into 2nd when I hit 3200" seems logical. I'll have to see what 3200 in 3rd equates to MPH. As far as folks thinking you never need to go to 1st, I suggest you pull the grades from Hot Springs NC over to Walnut NC, and see if you can do that without overriding the computer and manually downshifting. That is 9% on both sides of those two hills. With the new info (3200 rpm) maybe I can make it over while still in 2nd. Will test that idea in the coming week.

I am over 8000 miles on this trip out west through TX, NM, CO, UT, WY and then driving like hell to dodge the NE and SD and MN hail and tornadoes. Hail busted out all my vents in Colorado Springs. Yay. Currently in Indiana, trying to get back home to Fort Pierce, FL.

[Tystevens]

Teamfour wrote:
The way to fix that is to get a tow vehicle suitable for your towing needs. If the tranny is having to shift to first to get up a hill you are severely under powered.

Well, it depends on the hill, the road, etc. There are lots of routes here in Utah that put us in 1st gear, especially in our '05 w/ the 4 spd transmission, and I don't think we were severely underpowered. A 10% grade and 25 mph curves has low gears written all over it.

[Tystevens]

At 3500 rpm, you're just getting into the power band for that engine. If you look at a power output curve, you have to get to 4000-5000 rpm for max torque and hp numbers. We have put a lot of miles on our Chevy 5.3s above 4k rpms; you have to when towing with pretty much any small block V8. So I'd say let 'er rev -- you're not enjoying the full potential of that engine!

Re: downshifting, the transmission is programmed not to hurt anything when it downshifts. I would not worry about it.

[carringb]

PUCampin wrote:
Bryan, I am curious, do you know what gears the 6R75 locks up in? I know when I am going slow like through a parking lot, it FEELS like it is locked. It will "chuck" some with throttle tip in and out like when driving around my car in 1st. Same if I am driving in 1st or 2nd going up a hill and feather the throttle, tip in and out is not as smooth as I would think if the converter was unlocked. If in 2nd or 1st and I let off the throttle, the tach drops in a linear manner with the speedometer until I am almost stopped where it will pop up a little like the converter is unlocking.

Whatever it does, I really like how they drive. I just wish I had the full manual control like the later ones, I would love to lock out 6th but NOT 5th for towing on the flat.

I believe it does. I think all of the Ford with drive-by-wire lockup in all gears. The "pop" you notice during deceleration is probably the fuel injectors firing again. Normally during coasting your T/C is locked and the engine is completely de-fueled until it drops below a certain RPM.

If you get a 5-star Tuner, you can have a 6th-gear lockout enabled for towing. I know some guys like this feature for the 5R110 behind the V10, because it also does not have an overdrive lockout.

[Mike_LeClair]

I am kinda curious about your 3,500RPM ceiling as well. I tow with a diesel now and will take my 5.9 right up to 3,400 RPM red line when it is necessary to do so. When I ran gas units for towing I had no qualms about running the gas pots right up to 4,200 to 4,500 RPM depending on the motor being worked. My square bore 400CID Ford wasn't even sweating until 4,000RPM and she still had much more pedal to the floor if I needed it.

I think you should try "being one with your machine" and let the transmission make the decisions for you. If you are going up a mountain just keep the gas pedal down, to the floor if necessary, let the engine work and let the tranny logistics do what they do best. I agree that your 5.3 should NOT be struggling with a paltry 5,000lb trailer unless your are seriously way over weight with cargo, kids, dogs and an SO.

Service your tranny regularly, clean fluids and filters, adjust the bands and so on as required by your service manual and you should be good to go. If you are working the motor hard at, say, 4,200 RPM for an extended period of time, keep an eye on your gauges and react to any over temp situations. If you don't have a tranny temp gauge then get one installed and keep an eye on it.

Cheers!

Mike

[PUCampin]

Bryan, I am curious, do you know what gears the 6R75 locks up in? I know when I am going slow like through a parking lot, it FEELS like it is locked. It will "chuck" some with throttle tip in and out like when driving around my car in 1st. Same if I am driving in 1st or 2nd going up a hill and feather the throttle, tip in and out is not as smooth as I would think if the converter was unlocked. If in 2nd or 1st and I let off the throttle, the tach drops in a linear manner with the speedometer until I am almost stopped where it will pop up a little like the converter is unlocking.

Whatever it does, I really like how they drive. I just wish I had the full manual control like the later ones, I would love to lock out 6th but NOT 5th for towing on the flat.

[PUCampin]

OP states "max speed in 2nd is 45mph at 3500rpm"

This is part of the problem. Modern small block Overhead Cam V8s DO NOT have a ton of low end torque, most torque and power is made by spinning the motor. This is the opposite of the way V8s used to be and is disconcerting for those who have driven older big block V8s. Peak torque for the 5.3 is around 4400rpm, and peak power around 5300! At 3500 rpm you are falling off the torque curve and only making around 220hp.

DO NOT be afraid to put your foot in it and let the engine run, it may sound to you like it is going to blow up, it is not, and will happily spin at peak torque for a long time.

If the transmission is waiting too long to down shift into second, like 2500rpm, then it is letting you fall too far off the power curve and shifting down won't get you far enough back on it. I saw this all the time with my dad's old chevy truck Pre-empt it. When the tach hits 3200rpm manually drop it into second so you will hit second around 4200rpm and stay in the power band.

And no, something is not necessarily wrong if you have to use 1st. Depending on the grade, elevation, and axle ratio you could have to use it. 1st on the 4sp is not particularly low at 3.01, and you could likely have 3.39 axle gears. If you are talking 6% at 200ft, then yea, you should not need 1st, but somewhat mountainous driving with some elevation, yea. Going from Palmdale CA to table mountain was over a 5000ft elevation gain, even with my 6spd, I definitely had some 1st gear work, but it let the engine stay at 4000-4500rpm at peak torque.

[kaydeejay]

That 5.3 V8 is found in Suburbans, Tahoes etc and a LOT of pickup trucks. Most are heavier vehicles than the T'Blazer.
IMHO if your Trailblazer is struggling with a 5000# trailer, you have a much bigger problem that transmission shifting.
You need to get it checked out.
I pulled a 3500#+ boat with a Trailblazer with the 4.2L L6 (which has NO torque at the bottom end!) and while it wouldn't win any races, I had no problems approaching what you are describing.