Transmission issues while towing?

I got a 2000 tundra sr5 4.7l 4x4 and it struggles with towing. I try to use it to tow my 2001 ford mustang to and from the track and it just absolutely hates it. I know that these trucks aren't really designed to tow but cmon when you're floored and decelerating when trying to get onto the highway, it's a little ridiculous. Big v8 with 4 wheel drive should be able to pull my 3500 lbs mustang no problem. Hell, it has trouble towing my quad. Anyone know if this could be my transmission possibly going out? I did have to replace the transmission pump not to long ago due to it braking when when reinstalling the transmission when I replaced the rear main seal on it. And the truck does have 226k miles so I wouldn't be to surprised. But does anyone know how to make these better at towing, Or if it is my transmission going out on it? The truck also does struggle a little bit driving uphill even when it's not towing. And when I am towing, I do have overdrive off because I read that towing with overdrive on will blow the overdrive gear. Or maybe there's some modifications I can do to it to make it better? I've put too much money into this truck to get a better tow rig so any help will be appreciated.

 

Making sure your trans fluid is in good shape would be a good start. Also sounds like it would be good to keep an eye on your trans temps with a scan gauge or similar. Though I'm not sure a transmission issue is what's causing your problems.

 

The transmission fluid was just flushed about 1000 miles ago when I replaced the transmission pump. I also bought this truck off my girlfriends dad and my girlfriend learned how to drive with this truck. She also took it to the desert and did dounts almost every other day and her ex boyfriend was a wanna be mechanic and tried to do an oil change on it and drained all the fluid in the transmission and then proceeded to double up the engine oil. And then my girlfriend drove the truck about 100 miles like that. That's also why I'm thinking transmission is going out.

 

And the brakes are not up to the task either. I tow a M/C trailer and bike of maybe 750 lbs. or so total weight, and I know it's behind me. The engines aren't torquey enough, and the brakes are anemic. But they are reliable.

 

So he added the trans fluid to the motor? She drove 100 miles on an empty trans? Yikes!

 

I think I found the problem.

Big V8 displacements, expressed in units of tenth of a litre, begin with the number 7. Small block V8s run from 5.0 to ~5.9 with the 6s occupying a small-bore, big block segment.

What you have, in block parlance, is a sub-small or micro block generating a published 245hp and 315 foot/üllbs. And that's when the engine is fraesh... you may have some intake valve crud or filthy injector schnozzles subtracting from those values.

 

It would’ve only drained the pan, so [EDIT: not all the fluid] though I don’t recall what the pan holds exactly on the 4spd. I think there’s just under 4qt in the trans? The trans would be low and probably shifting funny, definitely would eventually cause damage. Not sure if it’d do it in a hundred miles, no more than having 13qt oil in the engine would!

There was one other guy on here who made this mistake, and I think he actually did nuke his trans, but it was on one of the later 5spd trucks like mine, not the older 4WD like OP’s

@SlowCars19 your best solution is probably in re-gearing front & rear. While it’s not impossible the trans is going out, it wouldn’t be too common at 200k-ish miles per other user experiences on here.

 

Overfill the trans fluid a little and report back. Is the torque converter a separate drain on ours?

 

It shouldn't be struggling that much, especially not with just a quad or "driving uphill".

Until I recently upgraded to a 5.7L 2019, I had the same truck as you... '00 SR5 4X4 w/4.7L V8 (Not a "Big V8" btw)

It towed my travel trailer @ about 5,500 lbs (W/huge frontal area) just fine. Not the fastest guy up the grade, but it performed very well for 6 years. I bought it with 155K and sold it with 205K.

Is that 3,500 lbs. of Mustang with or without the trailer?

That motor makes it's torque @ 3,400 rpm, and when towing I drove it from the tach and not the speedometer.

Sounds like there's something else going on... @ 245 HP/315 Tq those motors aren't making huge gobs of power, but I never had any problems. Do the shifts seem positive or slipping?
Maybe find a reputable trans shop and get it checked out. Most good ones will do free diagnostic.

 

4qts in the trans pan for a drain and fill, trans overall has closer to 10qts if doing a full replacement / flush.

 

Something isnt right.

no problems towing a 2500lb tractor on a 2000lb trailer.


Averaged over 14mpg.

Time your truck from 0-60. See if you can beat 9 seconds. Sans trailer, of course.

 

I’m trying to comprehend how one drains a transmission and not know it when the red fluid comes out? It should’ve been obvious when you start putting in the golden color of oil. I don’t foresee a great soon to be mechanic ex-boyfriend in the making.

Anyway, yeah get the tranny checked out by a professional. 100 miles with only 8 quarts of fluid instead of 12 with 4 quarts drained is going to cause issues. My experience in running a quart low can cause issues with the solenoids and harsh shifts.

How’s the shifting without towing otherwise?

 

I was going to ask if maybe the OP's girlfriend used to date @FlightSimGuy Related thread here: https://www.tundras.com/threads/transmission-fluid-question.117470/

On a serious note: OP, when was the last time you cleaned the MAF sensor? I really dirty one can have a MAJOR effect on performance.

 

Thanks for that - I had the 4 stuck in my head, but was drawing a blank if it was "1 and 4" or "4 and 10". Still haven't drain/fill'd mine yet, so I don't even have a reference for the 5spd.

 

Yeah, something is not right, unless the trailer for that mustang weighs 5,000lbs or something. I towed a 2002 4runner, on a trailer with mine....and yeah, it was there...but it was fine.

 

Hey! I never claimed to be a mechanic, I build log homes. A bit of a difference in materials.