Higher running temps after 2.79 to 3.80 swap

It could be coincidence, but my car wants to run at slowly increasing temps since Friday, when I rebuilt the rearend. Even if I drive slowly, so the car thinks it is still going 60, when my speedo says 85, it wants to heat up. Today, I swapped out my 160 degree thermostat to a 140, and swapped the 13lb cap for a 16lb, to keep the fluid from coming out at 220 degrees.

I have always run at 180-190, even dead summer heat in Houston. But since swapping the rear, it wanted to go to 230, starting to spew out the overflow hose at 220. Now with the new 140 thermo, it still runs at 205. I want my 180 back. Any suggestions as to why it is running hot?

Other than the new gears, no other changes have been made until I swapped the cap and thermo today. Temp outside was around 80 while driving, and the car is used to 90 and 95.

I am starting to think the transmission is running harder, due to the lower gears, and is heating up the radiator (trans lines run into the bottom of the radiator), leading to increased water temps. Does this sound logical? If so, I can buy a cheap trans cooler and solve the issue?

 

Hmmm . unless you were practicing burnouts with the new 3.80 and blew a head gasket ....

 

I doubt that the gears are the source of the increased heat...

 

I know the gears are not a source of the heat. I am more worried that the transmission is having to turn more to turn the gears at highway speeds, and the trans fluid is cooled through the radiator, and that heat is flowing into the coolant, causing the engine temp to increase. I have had blown head gaskets, and that is not what is going on here. I wish it was, as I would do some serious work while I was in there to increase my compression. Maybe mill the heads a bit, or swap them out for decent aftermarket heads. Maybe put shim gaskets in or something.

Nothing else has changed except the running temp after the rear gear swap, and it has to be something easy to fix. The coolant is new, within 500 miles, the radiator has been "reamed" and rebuilt at the same time. It ran 180-190 consistently, sometimes 200 if I sat at a red light for 3 or 4 minutes, but only during the heat of the summer. Until Saturday when I swapped the gears.

As far as "practicing burnouts" that is not an issue. With a 3.80 rear with a mini spool, "practicing" is not an issue. I can burnout just sitting at a red light with my RPMs up to 1600. Found out today on accident, when I was messing with "flashing" my converter. I was sitting at the red light, and slowly increased my RPMs to stall, and the rear started to swim to the left, which tends to be the direction of swim. Is the swim due to uneven air pressure in the tires? It has swam to the left since the conversion.

 

Maybe it's the sidepipes...

 

high temp

a decent tranny cooler is cheapand easy to put on...couldn't hurt, I put one on mine and temp dropped almost 30 degrees. you might look to see if moisture is in oil...never can tell...Jim

 

The sidepipes...riiiiight. You just won't give up on those pipes, will you. One day, we will meet in person, and I will buy you a beer, and we can personally argue the pros and cons of MY sidepipes.

I am starting to gain a fond affinity for you, TL. I hope our paths cross someday...

If I ever say something offensive to you, please recognize that I am a very friendly guy, but not all get my humor. I have not negative nor harsh feelings toward those who negate my projects. But, I LOVE to play the underdog and fight for what is right...one's desire to build what one wants!

If I ever do a ski trip to Colorado, I expect a meeting in a dark and shady location where we can meet and have a cold malty beverage together.

 

So, is a tranny cooler in my near future?

 

Lol@TL!

 

tranny cooler

couldn't hurt

 

wish i had put in a tranny cooler straight away. would have saved my tranny. your theory on heating sounds reasonable to me, and besides a cooler is cheap inshurance. that and a tranny temp gauge. ya don't know which port on c4 is out or in ????, me neither, any one else??? i'd recommend putting the aftermarket cooler on the return line for a happy tranny. do you have a thermal fan clutch, did it go as a freak coincidence???

 

I mentioned this on another thread...My Mav now outruns my 360 HP Dodge Hemi 1500. I always felt that the Hemi was the fastest vehicle I ever drove, but in the small Mav, it doen't feel as fast. Today, I put a pass on a guy after we both turned onto a highway that was two lanes but quickly turned to one lane. I passes his a$$ like he was sitting still, in second gear. Then I checked the timeslips on my Hemi, and noticed that the Mav is about 1/2 second faster...i was amped, since I always thought the Dodge was a very fast vehicle. I guess getting under 10 second 1/8 is my imaginary goal at this point. By the way, if I do 70 mph at 9.99 seconds on the 1/8th, what is my estimated 1/4 speed. It is a 40 mile drive to the closest 1/4 mile track (Houston Speedway) so I would like an estimate before I drive out ther and get my a$$ kicked.

I may have to try the trans cooler and see if I can drop my running temps. Should I mount it in front of, behind, or beside my radiator? My power-steering pump cooler is beside and to the left of my radiator. Shoud the trans cooler be to the right and behind?

 

for best result airflow should go grill, tranny cooler, a/c (if applicable), radiator. i think my tranny coller spec sheet said ya drop to 60-75% efficient by going behind radiator

a.k.a tranny cooler in front.

glad to hear yo mav rocks!!! i've been telling myself to put 3.80locker in for a while, i hate that one wheel wonder. how many r's ya spin at 55mph, 75mph

 

Ok, the long answer... I am a psychotherapist, and I get paid for the long answers, so here goes...

I got my wife to lead me to the racetrack on Saturday afternoon, after my rear rebuild. I told her (by cellphone) to go 30, 40, 50, 60, and 70 mph and put the cruise on, so I could follow and see what my 2.79 speedo gear said I was doing. At 30, my speedo said 40, at 40, 55, 50-65, 60-85, and 70-95. I am doing about 3250 RPM at 70. Not too bad for a part-time track car. My tires are 245-60r15, at about 26.5 diameter. A little slow for the track, but they average out for highway. I am thinking about 75% of original speed. On average. I called Ford and they said for every 5mph I lose, subtract a tooth from my speedo gear and we can correct the gears to the speedometer. I am not sure at what speed they are talking, but for the price of gears, I may try a couple.

My A/C is in the attic, since it makes the engine compartment much more cramped and ugly, especially with the shock towers in the way. Maybe after the tubular A-arm rack/pinion conversion, I might add the A/C back on. I need it in south Texas, but currrently drive after 6:00pm when the temp start to drop. The races don't start until 7:00 anyway.

It looks like a tranny cooler is in my very near future, to help cool down my radiator. I am guessing that is where my extra heat is coming from.

By the way, I always thought Aeon Flux was soo hot! Like your avitar(?) if that is what it is called.

 

Hey, I don't have anything against You either. You're a fellow Maverick enthusiast, and that makes you cool in my book. I'll be happy to help in any way I can. I just don't like sidepipes...