Normal for RPMs to rev up and down while braking?

When braking I noticed my rpms reving up and down, is that normal? Also sometimes it seems when going slow I guess it's a feather of the gas and the truck doesn't seem to move but the rpms go up. I just purchased don't want to bug the dealer. Thanks for those who help me.

 

Transmission is downshifting to assist in braking. Some cars to it, some dont. I think it helps on a pickup.

Not sure exactly what you're asking in the second question. Sounds like normal characteristics of an automatic transmission (and laggy throttle response on newer cars to get better fuel mileage numbers). The torque converter slips below it's rated stall RPM. It how you can sit at a red light with your foot on the brake in drive. I don't know what that number is, I'd have to guess around 1800rpm.

 

Sorry I'm not to knowledgeable about transmissions and the language required to communicate in car talk I'll do my best. But from what I get out of your message is it happens when the tourqe converter catches up with its self to Mach the speed of the car? And yea it seems to only be around 1 to 2 rpms when it happend then it kicks in the gear. Only seems to do it when being very light on the gas.

 

Sorry I ment 1k or 2k rpms*

 

This all seems normal.

 

Completely normal. This is the transmission downshifting as you slow, not only to help slowing down but to ensure you are in the right gear if/when you decided to accelerate again. Seems a little more pronounced on my 21' TRD pro vs my 15' TRD possibly just because I can hear the exhaust better.

 

There was speculation and maybe even an official Toyota response that they changed the shifting profile in the 19+ when they removed the trans cooler. This could be why it feels different.

 

That's right - blame everything on the missing trans cooler!

 

There was speculation and maybe even an official Toyota response that they changed the shifting profile in the 19+ when they made a decision that was contradictory to the previous 12 MY. This could be why it feels different.

I fixed it. No mention of the thing you speak of.

 

I was thinking of installing a Trans cooler. I won't be doing any heavy hauling for at least 3 years but I do have access to a trailer for up to 2 bikes. I was also ready you would want your transmission to heat up properly, and that driving to cool isn't good. So in that case just let the car warm up really good before towing?!? What's your thoughts on installing a Trans cooler?

 

sounds normal to me. I came from a manual tranny ranger so the behavior of the auto on this truck was making me question things like this as well but all seems to be normal. Really wish there was a manual option but what can you do.....

 

You’d install the oem transmission thermostat that doesn’t open until it’s warm. There’s also coolant lines running to the transmission that help it warm up. The cooler on your truck was called a warmer before 2019. There’s a lot of threads with speculation on adding a cooler and if you really need one.

 

A torque converter works by using a propeller-like disk driven by the engine to blow transmission oil at another propeller-like disk that connects to the transmission. A fan blowing a fan with liquid. There's more to it but the thing to remember is that it isn't a solid connection. That's why the engine speed can vary with throttle when the transmission isn't changing gears. At higher speeds under light throttle in high gears it uses a lockup clutch to force everything to turn together so it isn't pushing around the oil to move the vehicle anymore. Lowers temps and helps mpg. That's why when you're on the highway the engine speed doesn't flutter around when your foot isn't holding perfectly still.

 

They are called, Turbine and Impeller that is a fluid coupling to allow you to stop and idle in gear like at traffic lights, etc. The speed of engine changes the angle oil strikes the Impeller giving you about a 2.6 torque advantage, so as engine speed goes up so does the torque applied to wheels. The lockup clutch was not used in earlier days but was added in recent years after the VVT became standard to get the last bit of fuel savings.

 

Yeah, the truck is shifting down to use engine braking to assist slowing the vehicle. I have this one place on my way home, where I'm on a slight down hill, but I have to brake slightly for a dip in the road. The truck will down shift nicely and allow me to take my foot off the brake.