Has your trans thermostat failed yet?

[caulk04]

It seems mine is giving up the ghost.

'But you have a bypass valve installed, right?' Not currently. I've been playing with a new setup for a while now that I wanted to call a 'failsafe' thermostat. Using one of my aluminum caps and a custom spacer I had a setup that would remain partially open to the heater and cooler at all times and then open to full cooler and no heater operation at normal temp (~180). For over a year it's worked, seemingly invisibly.

Today though, the thermostat seems to have stuck shut or partially open. This was running down the highway 75-80 towing my sxs and a light trailer for 45min+ over hilly (not mountains) terrain. Within a couple minutes of surface streets it was down to 200 then over the next 15 minutes it was back to normal 180.

Seems that typically when the thermostat fails to open guys can see over 240° trans whereas mine settled here at a max of 222. Still unacceptable to me, so I'm going back to a full bypass and won't be offering this option.

 

[Wild one]

View attachment 572526

It seems mine is giving up the ghost.

'But you have a bypass valve installed, right?' Not currently. I've been playing with a new setup for a while now that I wanted to call a 'failsafe' thermostat. Using one of my aluminum caps and a custom spacer I had a setup that would remain partially open to the heater and cooler at all times and then open to full cooler and no heater operation at normal temp (~180). For over a year it's worked, seemingly invisibly.

Today though, the thermostat seems to have stuck shut or partially open. This was running down the highway 75-80 towing my sxs and a light trailer for 45min+ over hilly (not mountains) terrain. Within a couple minutes of surface streets it was down to 200 then over the next 15 minutes it was back to normal 180.

Seems that typically when the thermostat fails to open guys can see over 240° trans whereas mine settled here at a max of 222. Still unacceptable to me, so I'm going back to a full bypass and won't be offering this option.

To bad a guy couldn't find a bimetal spring like they used to use in thermostats that would fit in the bore,as they very seldom failed.I'm no fan of the pellet thermostats as they seem to fail way more then they should

 

[KansasArt]

To bad a guy couldn't find a bimetal spring like they used to use in thermostats that would fit in the bore,as they very seldom failed.I'm no fan of the pellet thermostats as they seem to fail way more then they should

I can attest to that statement!

 

[HEMIMANN]

Holy, moly man! You'd have to change trans oil @ 5,000 miles at those temperatures!

Like @Wild one says, the thermostat idea isn't inherently "bad", it's poorly-implemented. First off, you need a BIG thermostat so as not to restrict trans oil flow rate from design rate to and from the oil cooler radiator. 1st fail. Then it has to be RELIABLE, and it's not. 2nd fail.

Trans oil temp control is every bit as important as engine temp control, yet the only half-a$$ designed it. For my old RFE I just put in the bypass block and let 'er flow full time just like legacy trannys did. IDGAF if it's sluggish when cold.