55 mph on highways ?

[78 Chevyrado]

Wow Kenny, I'm glad that you're ok enough to post that!  Did the rager get charged?

It was several years ago.   I didn't even get a bump on myself...  old truck was heavy and I was holding the brakes as hard a i could.   he didn't move it much was why he left so much of his car behind.   Guy had no tag at all.  cops said likely a stolen car.   Rager got away.   I'm totally okay with that because it didn't step up to the next level.   any time things do step up to the next level I'm okay with it when only vehicles got damage.  I've wondered what happened tho to the other drivers that were involved in the pileup.  It was Sunday and there were several mini vans in there.   I hope they are OK.   

[berserk]

Edit: post rambles on so I removed it.

[Blazin]

I've run dozens of square bodies, & other trucks with everything from 235/85/16 to 35" rubber with 4.10 gears. 70/85 MPH no worries. You should figure out where the vibration is coming from though. If you're towing being a 1/2 ton you might want to keep it around 60, maybe 65 MPH though.
Are your tires E rated?

[berserk]

Edit: Starting thread for the specific issue I am having with vibration which is separate from this threads topic.

I agree, look at the post just before yours where I'm asking advice. Yes I have Mickey Thompson 10 ply E rated.

[AsolMarandy]

Many older trucks run like this on the highway. A TH350 with 4.10 gears and 33 tires will turn high rpm at speed. Running 55 is normal for that setup.

Staying in the right lane helps. Using hazard lights when traffic stacks up can help. Pulling over when there is space helps too.

Fixing the driveline vibration should be a priority. A vibration makes highway driving harder.

A gear change is an option later. A 3.73 or 3.55 gear will lower rpm. An overdrive swap like a 4L80E also helps, but it can wait.

Old trucks were not built for fast highway speeds. Watching the road ahead and letting others pass is the safest approach.

[zieg85]

I ran the 70mph with the 4:10 and a th400.  RPM's were up for sure but other than that easy peasy... I did eventually gear mine to a 3.21 and loved it.