Towing with Sienna/Rav4/Highlander? - Page 4 - Fiberglass RV


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 01-16-2013, 12:04 AM   #43
Senior Member
 
Glenn Baglo's Avatar
 
Name: Glenn ( second 'n' is silent )
Trailer: 2009 Escape 17B '08 RAV4 SPORT V6
British Columbia
Posts: 4,369
Quote:
Originally Posted by Mike Magee View Post
I don't recall seeing anything like that in my Highlander's manual. And I really can't imagine why the tranny would get hotter in 4th gear than it would in 3rd.
I didn't say it gets hotter in 4. I said my manual says to use 4 and not to tow uphill in 3 for an extended time. I'll dig out the book and quote the section tomorrow.
__________________

__________________
Glenn Baglo is online now   Reply With Quote
Old 01-16-2013, 12:28 AM   #44
Senior Member
 
Glenn Baglo's Avatar
 
Name: Glenn ( second 'n' is silent )
Trailer: 2009 Escape 17B '08 RAV4 SPORT V6
British Columbia
Posts: 4,369
The manual says: "Do not continue hill climbing or hard towing for a long time in the '3', '2' or 'L' position. This may cause severe automatic transmission damage from overheating. To prevent such damage, the '4' position should be used in hill climbing or hard towing."

This info was under Automatic Transmission, not under the towing section where one would expect to find it.

BTW, the grade on the Coquihalla Highway leading to the summit is generally 6-7 per cent but is 11 per cent on a short section ( which would be about where I got the warning light ).
__________________

__________________
Glenn Baglo is online now   Reply With Quote
Old 01-16-2013, 12:32 AM   #45
Senior Member
 
Brian B-P's Avatar
 
Name: Brian
Trailer: Boler (B1700RGH) 1979
Alberta
Posts: 5,000
Quote:
Originally Posted by Mike Magee View Post
And I really can't imagine why the tranny would get hotter in 4th gear than it would in 3rd. The lower gear is moving fluid through the cooler more quickly, I think, so it should do better.
I assume you meant "I really can't imagine why the tranny would get hotter in 3rd gear than it would in 4th", since that's the situation which Glenn described.

One potential reason is that the torque converter lockup clutch is only functional in some gears - at least the top gear, but probably not all the way down the range; my 5 speed Sienna locks up in at least 5th and 4th. Given a choice of locked up in 4th, or churning the unlocked torque converter in 3rd, 4th would run much cooler. All slippage in the torque converter - which is roughly 10% of the input shaft speed when in coupling mode - multiplied by torque transmitted is power lost. It may be about heat generation (by hydrodynamic losses), rather than heat dissipation (out the cooler).

Quote:
Originally Posted by Mike Magee View Post
I've had mechanics tell me that it's perfectly ok to run a vehicle all day long in a lower gear at, say, 4000 rpm, and that although it sounds noisier it's really easier on the drive train than using the higher gear.
That is likely true for some specific transmissions (and not the engine), especially old 4-speeds (most are 5 or 6 speeds now, and 8-speeds are becoming common). If you want to know how to fix something, ask a mechanic. If you want to understand vehicle design and operating procedures, there are better sources.
__________________
1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
STATUS: No longer active in forum.
Brian B-P is offline   Reply With Quote
Old 01-16-2013, 08:27 AM   #46
MC1
Senior Member
 
MC1's Avatar
 
Name: Wayne
Trailer: Nest fan, Airstream Sold
Ontario
Posts: 2,006
Quote:
Originally Posted by Francesca Knowles View Post

And can everybody please stop saying "SOB"???

In the first place it's rude,
Have a nice day!
For the record. The term "SOB" was coined as a short form for "some other brand".

For example.... If we sold our Airstream and bought an egg, the egg would be "SOB". If FK sold her egg and bought an Airstream, or Mallard, or Holiday Rambler, she would have "SOB".

There you have the "real story". No big deal.
__________________
MC1 is offline   Reply With Quote
Old 01-16-2013, 06:29 PM   #47
Senior Member
 
Mike Magee's Avatar
 
Name: Michael
Trailer: Li'l Hauley
Oklahoma
Posts: 5,143
Wow, hmm, I just always assumed that the TC would be locked up in any gear below the highest gear in which it's locked up. How weird! I wonder why they would engineer a tranny to lock up in 4th, but not in 5th, 3rd, 2nd...?

I just checked my Highlander manual, and it does not contain a similar warning against use of 3, 2, or 1 on grades. Perhaps its tranny is not the same as the Rav4's.
__________________
How much time do we have left? 2 Chr. 7:14
Mike Magee is offline   Reply With Quote
Old 01-16-2013, 06:52 PM   #48
Senior Member
 
Carol H's Avatar
 
Name: Carol
Trailer: 22' Airstream Formerly 16' Scamp
British Columbia
Posts: 11,731
Registry
Quote:
Originally Posted by Glenn Baglo View Post
BTW, the grade on the Coquihalla Highway leading to the summit is generally 6-7 per cent but is 11 per cent on a short section ( which would be about where I got the warning light ).
Yup the Coq has been known to take a few hostages....hot summer day is when you often see the wounded parked along the sides of the road, its a long long grade climb. I have only pulled across it twice and no warning lights but I now tend to take the slower scenic route when possible.

Its funny to hear that some cant lock on all gears - why is that? I can lock it on 4 & on down with the Subaru.
Carol H is offline   Reply With Quote
Old 01-16-2013, 06:55 PM   #49
Senior Member
 
Francesca Knowles's Avatar
 
Name: Francesca Knowles
Trailer: '78 Trillium 4500
Jefferson County, Washington State, U.S.A.
Posts: 4,543
Registry
I love my manual tranny...

Francesca
__________________
.................................
Propane Facts vs. Fiction:. Click here
Tow Limit Calculator: Click here
Francesca Knowles is offline   Reply With Quote
Old 01-16-2013, 06:58 PM   #50
Senior Member
 
Glenn Baglo's Avatar
 
Name: Glenn ( second 'n' is silent )
Trailer: 2009 Escape 17B '08 RAV4 SPORT V6
British Columbia
Posts: 4,369
Ya, well, when you are showing off, running up the steepest section, from the snowshed to the summit, with a loaded trailer in tow, and doing 60+ miles per hour in 3rd, you get what you deserve.
Done it many times in 4 and only dropped down to 55ish.
__________________
Glenn Baglo is online now   Reply With Quote
Old 01-16-2013, 07:08 PM   #51
Senior Member
 
Carol H's Avatar
 
Name: Carol
Trailer: 22' Airstream Formerly 16' Scamp
British Columbia
Posts: 11,731
Registry
Quote:
Originally Posted by Glenn Baglo View Post
Ya, well, when you are showing off, running up the steepest section, from the snowshed to the summit, with a loaded trailer in tow, and doing 60+ miles per hour in 3rd, you get what you deserve.
Done it many times in 4 and only dropped down to 55ish.
Yup you see the same thing in the Cascades, I always have a little giggle to myself if I pass someone broken down on the side of the road if they were one of the ones who flew by me earlier on.... I may not win a race but I do get to my destination without a big tow or repair bill
Carol H is offline   Reply With Quote
Old 01-16-2013, 08:49 PM   #52
Senior Member
 
Brian B-P's Avatar
 
Name: Brian
Trailer: Boler (B1700RGH) 1979
Alberta
Posts: 5,000
Quote:
Originally Posted by Mike Magee View Post
Wow, hmm, I just always assumed that the TC would be locked up in any gear below the highest gear in which it's locked up. How weird! I wonder why they would engineer a tranny to lock up in 4th, but not in 5th, 3rd, 2nd...?
I doubt anyone would build an automatic transmission that locked up in 4th, but not 5th - no one has mentioned one in this discussion as far as I see.

Why not the lower gears? Perhaps because conventional automatic transmissions (torque converter, planetary gearsets) are insanely complex, and it may be a mechanical design issue rather than just a control logic matter.
Perhaps it doesn't usually matter because lockup is only important when the torque converter is in coupling mode, which doesn't normally happen for sustained period in the lower gears.

Quote:
Originally Posted by Carol H View Post
I can lock it on 4 & on down with the Subaru.
Is it only a 4-speed auto?
Are you sure it locks up in first through fourth? I've never seen a torque converter lockup control available to the driver - only overdrive lockouts and tow/haul mode switches; I've never seen an indicator of lockup on an instrument panel. Most people have no idea what gear the transmission is using at any moment - let alone whether it is locked up - and even when I try to follow what is happening myself by watching engine speed it can be hard to tell in anything but a steady-speed situation.

We have one member here who couldn't tell the difference between his transmission shifting between 3rd and 4th (in a four-speed auto) and the torque converter clutch locking up... and I don't really blame him.
__________________
1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
STATUS: No longer active in forum.
Brian B-P is offline   Reply With Quote
Old 01-16-2013, 09:27 PM   #53
Senior Member
 
Carol H's Avatar
 
Name: Carol
Trailer: 22' Airstream Formerly 16' Scamp
British Columbia
Posts: 11,731
Registry
Quote:
Originally Posted by Brian B-P View Post
Is it only a 4-speed auto?
Are you sure it locks up in first through fourth? <cut>
We have one member here who couldn't tell the difference between his transmission shifting between 3rd and 4th (in a four-speed auto) and the torque converter clutch locking up... and I don't really blame him.
All I can tell you Brian is that when I take it out of automatic and into what Subaru calls "Sport Mode" the indicators on the dash light up and tell me its in Sport Mode and and it only has 4 gears to choose from & what ever gear its in reads out very clearly on the dash. If its in 2nd gear for example there will be indicator reading a big red 2 and the car will red line just like a manual transmission unless I manually shift it out of that gear. Use it all the time. Perhaps I'm mistaken as to what lock out is? Assumed it meant you locked into a gear and it would not automatically shift to another. Either way I shift into Sport Mode when I dont want the car to go into overdrive which it does in Auto mode or to stop it from hunting up and down for gears on a hill.
Carol H is offline   Reply With Quote
Old 01-16-2013, 10:12 PM   #54
Senior Member
 
Brian B-P's Avatar
 
Name: Brian
Trailer: Boler (B1700RGH) 1979
Alberta
Posts: 5,000
Quote:
Originally Posted by Carol H View Post
All I can tell you Brian is that when I take it out of automatic and into what Subaru calls "Sport Mode" the indicators on the dash light up and tell me its in Sport Mode and and it only has 4 gears to choose from & what ever gear its in reads out very clearly on the dash.
...
Perhaps I'm mistaken as to what lock out is? Assumed it meant you locked into a gear and it would not automatically shift to another. Either way I shift into Sport Mode when I dont want the car to go into overdrive which it does in Auto mode or to stop it from hunting up and down for gears on a hill.
Thanks Carol, that answers my question.

The discussion Mike, Glenn,and I were having was about torque converter lockup - a clutch engaging inside the transmission which locks the input side of the torque converter to the output side, eliminating slippage for efficiency and thus reducing heat generation under heavy load such as towing. That's completely unrelated to locking out - or disabling - the higher gears (such as by choosing the lower-numbered positions of a traditional automatic shifter)... which is still not quite the same as manually selecting a specific gear (as you do with the Subaru sport mode)

In short: you don't know if it is lockup up the torque converter, and confusion on the subject of transmission design and operation is understandable.

You may have a 5-speed which offers only 1st through 4th in Sport mode, because you are only expected to use that mode when high power is needed.
__________________
1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
STATUS: No longer active in forum.
Brian B-P is offline   Reply With Quote
Old 01-17-2013, 01:35 AM   #55
Senior Member
 
Carol H's Avatar
 
Name: Carol
Trailer: 22' Airstream Formerly 16' Scamp
British Columbia
Posts: 11,731
Registry
Quote:
Originally Posted by Brian B-P View Post
You may have a 5-speed which offers only 1st through 4th in Sport mode, because you are only expected to use that mode when high power is needed.
Actually really dont want to or need to know how it all works, just that it does. but I do know I have 5 speed or as I like to call the 5th rightly or wrongly, overdrive, when in auto. Only way I know to stop it from hunting around or going into overdrive, is to put it into 4th manually. Was also told by the dealer it was the best gear for me to use on long climbs etc.... which makes me think it probable does also have torque converter lockup in 4th at least.
Carol H is offline   Reply With Quote
Old 01-17-2013, 04:09 AM   #56
Senior Member
 
Jared J's Avatar
 
Name: Jared
Trailer: 1984 19' scamp
Kansas
Posts: 1,610
Torque converter lockup can get goofy. The Titan locks in fourth and fifth, BUT&hellip;if its in fifth (overdrive) and downshifts to fourth, it is only partially locked up in fourth. If you manually shift it to fourth, it's fully locked.

This is one of the reasons why it's best to manually downshift, if its going to be in a lower gear for a bit. That also keeps the heat down.
__________________

__________________
Jared J is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Towing with a rav4 Jimmy jones Towing, Hitching, Axles and Running Gear 5 08-13-2012 11:52 PM
Highlander towing ability ginnymce Towing, Hitching, Axles and Running Gear 7 10-17-2011 07:28 AM
Towing with Rav4 Edward Shook Towing, Hitching, Axles and Running Gear 1 07-08-2008 08:19 PM
Towing with Toyota Sienna 3.3L Alan P. Problem Solving | Owners Helping Owners 7 05-29-2007 11:31 PM
Better tow vehicle. Highlander vs. Sienna van Gary Little Problem Solving | Owners Helping Owners 6 08-31-2006 12:49 PM

» Upcoming Events
No events scheduled in
the next 465 days.
» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 11:39 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.