Can an aftermarket bumper cause excessive transmission temps?

[phattyduck]

Thank you again for the detailed explanation. Can you tell me what is meant by a "slipping" torque converter? Are you saying that even if the transmission is staying in 4th, the torque converter may still not be fully locked causing it to generate more heat? My apologies if its a silly question but I don't know much about automatic transmissions.

Yes, that's exactly it. Pay attention while accelerating on to the freeway - you'll actually feel/see 4 'shifts' on a 4-speed transmission. The last 'shift' you feel is the torque converter locking, and acts like a '5th' gear. At that point, applying more or less throttle (to a point) will keep the engine RPM locked to road speed. When the torque converter is unlocked, engine speed can/will go up and down related to throttle, not just road speed.

And unlocked (slipping) torque converter is how the engine stays running while stopped in 1st gear, how gear changes are smoothed out, etc. The slipping is good for smoothness/control, but bad for efficiency (most modern high-gear-count auto transmissions lock in every gear but 1st).

-Charlie

 

[Option01]

Yes, that's exactly it. Pay attention while accelerating on to the freeway - you'll actually feel/see 4 'shifts' on a 4-speed transmission. The last 'shift' you feel is the torque converter locking, and acts like a '5th' gear. At that point, applying more or less throttle (to a point) will keep the engine RPM locked to road speed. When the torque converter is unlocked, engine speed can/will go up and down related to throttle, not just road speed.

And unlocked (slipping) torque converter is how the engine stays running while stopped in 1st gear, how gear changes are smoothed out, etc. The slipping is good for smoothness/control, but bad for efficiency (most modern high-gear-count auto transmissions lock in every gear but 1st).

-Charlie

Oh wow, that is super good to know, thank you again! I'll definitely keep the OD off on my next trip up the mountain on Friday. It'll be a loud trip with the 4.88 re-gear and my already-embarrassing gas mileage will likely suffer but it'll be worth it if I can keep those transmission temps in a more reasonable range.

 

[Endlessblockades]

Thank you for the detailed info!

It's interesting that you were seeing such high temps even with the stock bumper. I do have a new radiator/cap installed but maybe I should look into replacing the thermostat? I'll track the engine temps on the way up the mountain on Friday and that should shed some additional light on my situation.

Either way, it sounds like adding an aux transmission cooler is a no-brainer but it would be nice to isolate/fix any other issues that might be contributing to my high temps.

I'm not sure if you mentioned your engine coolant temp earlier, but it's part of the puzzle and well worth popping to 3 bolts on the water inlet and making sure the jiggle valve is at the bottom of the TStat. I know it gets argued about a lot and doesn't seem to have much effect for some (I take their word for it), but I dropped 12 degrees (coolant) immediately and for evermore.....

 

[Romeo1]

Yes, that's exactly it. Pay attention while accelerating on to the freeway - you'll actually feel/see 4 'shifts' on a 4-speed transmission. The last 'shift' you feel is the torque converter locking, and acts like a '5th' gear. At that point, applying more or less throttle (to a point) will keep the engine RPM locked to road speed. When the torque converter is unlocked, engine speed can/will go up and down related to throttle, not just road speed.

And unlocked (slipping) torque converter is how the engine stays running while stopped in 1st gear, how gear changes are smoothed out, etc. The slipping is good for smoothness/control, but bad for efficiency (most modern high-gear-count auto transmissions lock in every gear but 1st).

-Charlie

Excellent explanation [MENTION=139000]phattyduck[/MENTION].

Listen and feel for the lock/unlock.

With the torque converter "unlocked", power transmission occurs only by fluid coupling. Pretty neat how it works really. It also allows for "torque multiplication."

With it "locked" it behaves much like a clutch in a manual transmission. It's a physical, direct, and very efficient method of transmitting torque when underway in certain conditions.

If you ever have an automatic transmission vehicle buck violently when coming to a stop, the converter is failing to unlock appropriately.

 

[thezentree]

Haha! Yeah I probably will end up doing both but adding holes to the bumper is going to be messy since the bedliner coating was already applied. I asked my wielder friend who built the bumper for me and he says he can add holes behind the decorative slots in the front plate but he said it may not be pretty so I was hoping I might be able to avoid going that route by installing an aux trans cooler. But there's still a lot of radiator and AC condenser down there as well that could also use more airflow so I'll probably do it.

These are the cuts I made. I made the slot first, and later added round holes where the red circles are. I'm sure there's a lot of stagnant air behind the bumper's bash plate at road speeds but at least the fan can pull air through.

The OD off stuff phattyduck is talking about will also make a HUGE difference on grades and in traffic.

 

[96RedRunner]

Do you also have an extra transmission cooler or are you staying below 190 with the stock transmission cooling?

Bypassed cooler in radiator using the B&M 70264, use OE skid plate I cut 6 1-1/4" holes in leading edge
As others have mentioned make sure thermostat is clocked correctly.

 

[19963.4lsr5]

I always try to drive at a speed to get lockup if I can. With 4.10’s lockup is 48mph in 4th or around 41mph in 3rd.

I’m partial to the TrueCool 4589 for bypassing the Rad. But it will require relocating the horn.


Sent from my iPhone using Tapatalk

 

[phattyduck]

Oh wow, that is super good to know, thank you again! I'll definitely keep the OD off on my next trip up the mountain on Friday. It'll be a loud trip with the 4.88 re-gear and my already-embarrassing gas mileage will likely suffer but it'll be worth it if I can keep those transmission temps in a more reasonable range.

3rd with the torque converter locked is only a few hundred RPM higher than 4th unlocked - it won't be much different in sound. Obviously on the flats and mild hills, leave OD on...

Under load, a little more RPM is almost always a good thing - the water pump and fans spin faster (more cooling), the engine torque requirement is lower (hp = RPM x torque) which is better for engine, and it is better for transmission heat (no or less torque converter losses). 3rd locked will be *better* for mileage than OD unlocked - along with being better for the rest of the drivetrain.

For the same set of reasons, 4LO is better when going slow offroad.

-Charlie

 

[Option01]

3rd with the torque converter locked is only a few hundred RPM higher than 4th unlocked - it won't be much different in sound. Obviously on the flats and mild hills, leave OD on...

Under load, a little more RPM is almost always a good thing - the water pump and fans spin faster (more cooling), the engine torque requirement is lower (hp = RPM x torque) which is better for engine, and it is better for transmission heat (no or less torque converter losses). 3rd locked will be *better* for mileage than OD unlocked - along with being better for the rest of the drivetrain.

For the same set of reasons, 4LO is better when going slow offroad.

-Charlie

Oh dang, sounds like OD off is pretty much good for everything when traveling a consistent incline. Any idea if ECT does any good or harm in that situation? Since I re-geared to 4.88, I've been thinking of leaving it on all the time since it feels a little better when accelerating from a stopped position (it feels like it jumps into 2nd gear a little too quickly and ECT seems to help a bit with that).

BTW, thank you again for all you super-informative answers! Without helpful people like you and the other posters on this forum, I'd probably be dealing with a busted transmission in the near future.

 

[mtbtim]

Bypassed cooler in radiator using the B&M 70264, use OE skid plate I cut 6 1-1/4" holes in leading edge
As others have mentioned make sure thermostat is clocked correctly.

I was actually thinking of cutting holes in my front skid plate and the bumper itself to increase air flow, but I'm leaving that as a last resort until I see how well the Koyorad aluminum radiator performs in adverse conditions.

 

[phattyduck]

Oh dang, sounds like OD off is pretty much good for everything when traveling a consistent incline. Any idea if ECT does any good or harm in that situation? Since I re-geared to 4.88, I've been thinking of leaving it on all the time since it feels a little better when accelerating from a stopped position (it feels like it jumps into 2nd gear a little too quickly and ECT seems to help a bit with that).

BTW, thank you again for all you super-informative answers! Without helpful people like you and the other posters on this forum, I'd probably be dealing with a busted transmission in the near future.

From a transmission longevity standpoint, it won't make much difference either way. Many on here drive in "power" mode all the time.

-Charlie

 

[IconicFJ_]

I sell the 4runner transmission cooler kits. I hear from my customers they can reduce the temps by 30 degrees F or more.

1996-2002 4runner Transmission Cooler Bracket Kit
– Iconic Fabrication

 

[mtbtim]

I sell the 4runner transmission cooler kits. I hear from my customers they can reduce the temps by 30 degrees F or more.

1996-2002 4runner Transmission Cooler Bracket Kit
– Iconic Fabrication

That's cool you make a bracket for transmission coolers. I tell you what, I'll link your kit in the video description of two videos I have on the subject. Look at the parts list and you'll see the link to your bracket.

External Transmission Cooler Install (3rd Gen 4runner/1st Gen Tacoma) - YouTube

Transmission Cooler Install with Radiator and Thermostat Replacement - YouTube

 

[Romeo1]

From a transmission longevity standpoint, it won't make much difference either way. Many on here drive in "power" mode all the time.

-Charlie

[MENTION=139000]phattyduck[/MENTION] or anyone else, Is there a definitive consensus on what exactly the ECT does? It obviously raises shift rpm's, but does it change the torque converter lock up strategy? Does it change anything else like say fueling tables or anything if the sort?

I want to say in the several hours I've spent searching that topic, I think there's only one thread that actually goes into it specifically. I should have probably booked marked it....

 

[Option01]

I sell the 4runner transmission cooler kits. I hear from my customers they can reduce the temps by 30 degrees F or more.

1996-2002 4runner Transmission Cooler Bracket Kit
– Iconic Fabrication

Oh man, I really like your kit but it looks like it might not fit on my 4runner as my bumper overlaps the rail that the lower section of your bracket attaches to. Or am I maybe looking at it the wrong way?

 

[96RedRunner]

my 4runner as my bumper overlaps the rail that the lower section

Was looking at pic you really should clearance the cutout around freon line or bend line.
Condenser flex's with body bumper rigid with frame it will rub a hole in the line.

 

[96RedRunner]

I was actually thinking of cutting holes in my front skid plate and the bumper itself to increase air flow, but I'm leaving that as a last resort until I see how well the Koyorad aluminum radiator performs in adverse conditions.

Best way to go about it if you want to find out cause and effect of mods.
OE skid covers 1" of fins and bottom cap right at 3" of radiator noticed temp difference with it off.
OE skid better than nothing and it's enough for wheeling I do.

 

[IconicFJ_]

Oh man, I really like your kit but it looks like it might not fit on my 4runner as my bumper overlaps the rail that the lower section of your bracket attaches to. Or am I maybe looking at it the wrong way?

Thanks! Yes you are correct, my bracket won't work with that bumper. Is it a Coastal Offroad?

 

[phattyduck]

[MENTION=139000]phattyduck[/MENTION] or anyone else, Is there a definitive consensus on what exactly the ECT does? It obviously raises shift rpm's, but does it change the torque converter lock up strategy? Does it change anything else like say fueling tables or anything if the sort?

Shift points, mainly. It *might* have a slight effect on lockup, but its minor. Absolutely no change in fueling or timing tables for the engine.

-Charlie

 

[phattyduck]

Oh man, I really like your kit but it looks like it might not fit on my 4runner as my bumper overlaps the rail that the lower section of your bracket attaches to. Or am I maybe looking at it the wrong way?

Where there's a will, there's a way. Grinder to the bumper, mount the cooler on the back side, spacers as needed, etc. There's plenty of room left in there for a trans cooler.

I custom mounted my cooler - it sits behind everything, right next to the AC condenser so the fan pulls as much air through it as possible. Modified the upper and lower condenser mounts, etc. I also used a thermostat on the cooling system to minimize overcooling in the winter. There's now a winch control box in there, and it all still fits...

-Charlie