High RPMs at highway speed

Driving to work today my truck (2010 trd off road 2 wheel drive) was having very high rpms, I attached two pictures. When I took my foot off the gas the RPMs would drop to 1000. As soon as I started pushing down on the accelerator again, the RPMs would jump back up to 3/4000. I recently had to replace the rear differential. While it was in the shop they also replaced the leaf springs due to the recall. Could replacing the differential have caused this rpm problem? I have a 35 mile drive to work and I feel like that distance at 4000 RPM is not going to work for very long. I looked into changing the transmission fluid here on the forums and it seems like I should never have to do that. I also sometimes get the axle wrap problem when stopping and starting. I am planning on using the U-bolt fix I found on here for that problem. I made sure that I was in drive and not 4. I am kind of at a loss.

 

FYI the maintenance light has been on since I got it back from the shop.

 

That sounds like your transmission isn't in O/D no matter what the light says, but that it's stuck in 4th or even 3rd.

 

Is it possible when they replaced the diff that they replaced it with a different gear ratio?

 

A quick experiment...next time driving at lower highway speed, like 45-55, shift from O/D to 4th and see if the RPMs change. If it does, it's not the tranny. If nothing happens, then you might be stuck in 4th.

 

I am going to try switching it into 4 then back D on the way home and see if that is the solution. Having just spent 3k on the differential I really don't like the idea of repairing the transmission. I will also check the gear ratio, it was stock before and was replaced with what was supposed to be a brand new stock differential.

 

The switching to 4 then drive didn't work. This seems to occur when I go over 60 miles an hour or half to accelerate quickly, and then it doesn't fix itself until I park turn off the car and turn it back on. The whole turn it off turn it back on thing makes me wonder if it's a computer issue. Will be taking it into the shop later today. Also last night when it occurred all these extra warning lights came on.

 

I'm guessing your truck is a v6 and the shop put in a diff for a 4 cylinder Tacoma. Time for 35s

 

If your truck is 4x4, don't use 4x4 until they put in the correct diff - you'll blow up gears.

The 35s comment above was obviously a joke.

 

Very weird. Interested to see what the issue is. Good luck.

 

The truck is 2 WD, by the way...

 

Yeah I'd guess gear ratio but those lights make it seem like the computer could be a problem too like you're saying. Interested to hear the answer, I've had reason to suspect questionable electrical on more than one occasion too.

 

The stock final drive ratio for a 2010 V6 is 3.73:1, it would have to be double that to account for the 3800 rpm the OP is showing at 65 mph.

 

I would lean more towards it being something with the transmission before i would believe that its a different gear ratio.

 

From a dead stop, count how many upshifts you have, this will tell you what gear you're in.

 

Get the DTCs read, that will tell you a lot...

Also in skimming your posts I read that you paid $3k for a differential--what the heck did they do to it that was worth $3000 ?

 

I think the truck is in limp mode.

 

I had a similar problem to yours @jmc1131.

One evening I was driving and hit a rather deep pothole; it kicked my truck out of 5th into 4th and refused to up shift. No engine code, and for about a month the problem was intermittent, happening maybe 50% of the time I was driving. I took it to a transmission shop, they couldn't figure it out, I took it to a local automotive electrical expert, and the issue went away after cleaning and re-connecting all my transmission wiring. Electrical guy said it ended up spitting the code P0748 - Pressure control solenoid A electrical. Code ended up going away when I fired the truck up the next day, and hasn't been back since.

 

Disconnect a battery cable to clear the code and let us know if it runs normal.

 

Wiring connections would be one of the things I would check first, especially after having work done...