Q to those who purchased new lifted trucks with 35's and 3.21, question about AT shifting to 8th

[Elijah]

Over these past years dealerships have been selling lifted trucks. Based on the window stickers I've seen they have come with either 3.21 or the 3.92 gearing.

I have a question

1. Have you noticed when on the highway it not seeming to shift to 8th a lot?

It is so odd. I drive the same way to work everyday. Some days it shifts to 8th right away but then again like today it did not get to 8th at all.

13 miles to work and I'd say 10 of them are highway.

 

[rwhjr]

35s and 321s and I have no problems with my truck going to 8th gear

 

[ThunderMug95]

Yeah, its common for my dealer to have a new one with 37’s and 3.21’s. The 8spd trans works very well for turning 35’s w/3.21’s. My truck came stock with 31.4’s (17’s)and it was a rocket and never hunted btw 7/8 unless I was going up a noticeable grade. Current set up is 33.2” tire on my 3.21’s and it will hold onto 7th a lot longer, but 7th and 8th are both sub 1:1 anyways

 

[WilliamS]

I had 3.21s and 35s for 4 years and it still shifted to 8th just fine. It would slip out pretty easy to 7th gear on overpasses and such but 8th while cruising flat out was never an issue. Still maintained about 18mpg on average with 80 highway / 20 city mix at 70+mph in Florida.

 

[Elijah]

The roads are pretty flat here. Very mild inclines. When it hits 8th I too get about 20 - 21.5 mpg on my 35s.

I'm just not clear as to why it is so hard for it to get to 8th.

Any suggestions?

 

[rwhjr]

The roads are pretty flat here. Very mild inclines. When it hits 8th I too get about 20 - 21.5 mpg on my 35s.

I'm just not clear as to why it is so hard for it to get to 8th.

Any suggestions?

That’s pretty vague. What speed is it shifting into 8th at.

And if you expect to pass people on the highway in 8th with the setup we have then that’s not gonna happen

But I don’t see why that would even matter since it’s an auto and does it’s thing without you having to do anything...

 

[Elijah]

That’s pretty vague. What speed is it shifting into 8th at.

And if you expect to pass people on the highway in 8th with the setup we have then that’s not gonna happen

But I don’t see why that would even matter since it’s an auto and does it’s thing without you having to do anything...

1st : No I'm not trying to pass people.
2nd : Just maintaining any highway speed

For example this morning on one stretch of highway I was doing a steady 65mph. Did not shift to 8th.
Then after getting onto another highway I was at 50mph still did not shift to 8th.

But then there are just as many days driving the same highway where it is shifting to 8th.
I'm light footed so I don't drive gas on and gas off.

Appreciate your response

 

[alainwow]

I had 3.21s and 35s for 4 years and it still shifted to 8th just fine. It would slip out pretty easy to 7th gear on overpasses and such but 8th while cruising flat out was never an issue. Still maintained about 18mpg on average with 80 highway / 20 city mix at 70+mph in Florida.

Dude I’m in Miami and I’m lucky if I get 13 Mostly highway too...

 

[NoveskeFan]

Just curious. My truck is stock with 3.21’s. If I’m just cruising along it will shift into 8th gear once I hit 55mph. What speed are most people with 35” tires seeing the 8th gear shift at?