Transmission thermostat/potential trans issue

[mun52022]

Hey, ive seen others without a thermostat in the trans, but couldn't find any write ups. Is it worth it, or possible to remove the thermostat or not really?
I've noticed that when my trans is cold, anything below °120, it shifts like butter. But anything higher it shifts hard into 4th and only 4th, also I've noticed Here recently that when I'm driving in normal drive, and I have to get on the gas a little to merge into traffic, it will hesitate to downshift. Then downshift very very hard. It did it once and it was so hard I thought something broke, then the engine was unresponsive for a few seconds then everything was fine. Very confusing. I looked up normal leadframe issues and my issues don't seem to be the same. I have been driving it in manual mode and it's been perfectly fine other then shifting firm into 4th and only 4th when above about 120. Anyone else had this happen or know what I should do? No codes, going to check connections and wiring to trans soon. Thanks everyone. Really hope to figure this out
Truck is a 14, has a whipple and some other stuff done. Probably has a trans tune but I have no clue who's.

 

[MurderedOutSVT]

Nit sure what you are trying to accomplish by removing the t-stat. Sounds like a valve body issue

 

[The Car Stereo Company]

hows the oil level?

 

[mun52022]

Oil level is good. I did a filter/fill, a month ago. it did all this before though, looked clean inside, not much material on magnet.

 

[MTF]

Not knowing how it was driven from the previous owner doesn't help.
Not knowing what tune is on the truck doesn't help either.

First, I would try and track down the Handheld Tuning device from seller.
Or start calling, Whipple, JDM, 5-Star, Livernois and see if any of them made a Tune for the truck using your Vin#.

Normal operating temp of the trans is 200. 170 to 230 (230 is max and should not be driven hard till it cools down).
Keep in mind 170 is when the tranny's fluid thermostatic coupling opens.

If you normal drive in manual often and have since you got the truck.
It could be the transmission learning cycle hasn't completed (and I mean maybe).
It does take about 300 miles to complete a learning cycle with mixed driving in D mode.

Lead Frame/Valve Body/Clutch packs/Bands, would be the most likely candidates.

 

[PoolManRaptor87]

So my trucks got about 230k. Trans has 100k. Was replaced at 50k, and I beat the **** out of it for 50k while neglecting my trans service. Honestly, it was the one fluid I didn't change upon purchase, and the trans ran so cool and shifted so damn good I overlooked it until it was too late. Got a soloniod code, started over heating in higher gears. Reset codes, started driving in manual avoiding top gears while waiting for fluid,parts, and time. 1k later I drained trans, rebuilt valve body with sonnax shift kit, trans go shift kit(which it already has), superior trans thermostat cooler delete, and Amsoil fluid. Got another 3k in Manuel avoiding 5-6 gear and long highway trips. Now my trans is overheating in 4th after roughly 15-30 mins depending on driving conditions. Back roads in 1-3 I don't get over 170 degrees.
I put off my trans service way too long for how I drive. I'm WOT everywhere. Self employed. And late to everything and where where I'm needed, everyday, all the time. Also do all my own vehicles maintenance for myself, company, and family.
Long story short,
I'm throwing in a cheap used high mileage trans to get her back into work daily with me. Since working out of the wife's vehicle is very taxing, at work and at home.
Then rebuilding my current trans with a new TC for install next spring.
But there is now way I would have gotten another 4k out of my trans without the low temps from the trans thermostat delete.
I'm 100% Installing in my new high milage trans, and my rebuilt one. As long as your cooler lines still go threw your radiator, temps still get to 180-185. After an hour or so of easy driving in 80 degree weather. As your trans fluid transfers heat with coolant in the rad. But the difference it made in trans temps was 4x what an additional trans cooler did. Additional trans coolers really don't do squat when the thermostat doesn't open till 190-195, if it doesn't get stuck closed all together.
Will never run without a
STL009 by Superior trans cooler delete
Or a trans go shift kit
Ever.

 

[TomDirt]

I'd hate to R&R that transmission 2X if I didn't have to. Around here I found a reputable shop to do a bench rebuild (all oem parts) for $2500.