55 top speed

[Mandoguy]

Thanks guys for all the posts, when I said “55 top speed” I ment 55 was a comfortable cruzing speed. I have 265-75-16’s on my truck as in the avatar pic,I drove the truck with the stock wheels 235-85-16’s for a few months and it was running high RPM’S at 55 also. I don’t have a tach so I’m not sure on RPM’s.Could my Quadrajet carb be holding me back? I don’t see how I could go to a taller tire short of changing wheels,,,the 85 series I had on it never helped.

 

[Dougnsalem]

Thanks guys for all the posts, when I said “55 top speed” I ment 55 was a comfortable cruzing speed. I have 265-75-16’s on my truck as in the avatar pic,I drove the truck with the stock wheels 235-85-16’s for a few months and it was running high RPM’S at 55 also. I don’t have a tach so I’m not sure on RPM’s.Could my Quadrajet carb be holding me back? I don’t see how I could go to a taller tire short of changing wheels,,,the 85 series I had on it never helped.

If you think that's so horrible, then try running 215/85R16's with 4.56 gears and a big block. I think getting a tach first, would be your best bet. (This is ment as a serious recommendation. Not demeaning in any way....)

EDIT: And I pull my camper at 65 to 75mph for extended trips....

 

[Frankenchevy]

Thanks guys for all the posts, when I said “55 top speed” I ment 55 was a comfortable cruzing speed. I have 265-75-16’s on my truck as in the avatar pic,I drove the truck with the stock wheels 235-85-16’s for a few months and it was running high RPM’S at 55 also. I don’t have a tach so I’m not sure on RPM’s.Could my Quadrajet carb be holding me back? I don’t see how I could go to a taller tire short of changing wheels,,,the 85 series I had on it never helped.

Those tires are within a few mm of theoretical height. Ones just wider. 265mmx1.5+16 or 235x1.7+16 is within 2mm.

 

[Frankenchevy]

Tire size is the easier way for most people to better their final ratio for top speed. From what I gather from your comments, you’ll probably want a shop to swap your gearing for you. Not to say you couldn’t pull it off, but I’d at least find a buddy who’s done it once or twice.

You’ll need to do both axles and 4.10 is probably the cutoff for carriers. So you’ll need to swap it all to go taller than 4.10

 

[Dougnsalem]

If you want you'r cake and eat it too, as in don't want to lose torque, but want lower rpm at a higher speed, there's only 2 ways to accomplish this. Either taller tires, or overdrive. However, taller tires tend to eat up that torque too. If it's a 2wd, I'd be highly considering a 4L80-E. Gear Vendor is an option too but very expsive not only for the unit itself, but the mods to make it work as in driveshaft work, crossmember moving and/or addition etc.

You don't even look at the profiles before you post a reply, do you? He has a K20....

 

[HotRodPC]

You don't even look at the profiles before you post a reply, do you? He has a K20....

Nope, sure didn't. Didn't know it was 3/4 ton and didn't know it was 4x4. Some people don't have profiles. Some don't even mention it. Some have acquired other squares not even talking about the truck in the profile. Not a bad start for an assumption though.

 

[Dougnsalem]

Nope, sure didn't. Didn't know it was 3/4 ton and didn't know it was 4x4. Some people don't have profiles. Some don't even mention it. Some have acquired other squares not even talking about the truck in the profile. Not a bad start for an assumption though.

Why, thank you, kind sir.

 

[dajn37]

I have only taking my 87 v20 around the block. TBI 350 and th400 trans. I need to look to confirm but most likely 4.10. Cant believe I haven't confirmed that. Anyway, I couldn't believe how smooth it shifted. But now I am curious about 55 to 60mph cruising also. In high gear before 30mph. Could barely feel both shifts. I remember being surprised I was in high gear already. I only got up to 50mph. To be honest, I think your overly concerned about rpm. Those 350's can handle it pretty good.

 

[Frankenchevy]

I have only taking my 87 r20 around the block. TBI 350 and th400 trans. I need to look to confirm but most likely 4.10. Cant believe I haven't confirmed that. Anyway, I couldn't believe how smooth it shifted. But now I am curious about 55 to 60mph cruising also. In high gear before 30mph. Could barely feel both shifts. I remember being surprised I was in high gear already. I only got up to 50mph. To be honest, I think your overly concerned about rpm. Those 350's can handle it pretty good.

You can adjust the vacuum modulator on your TH400 to modify the shifts a bit.

 

[dajn37]

I have a long ways to go before that thing is ready for the road. I am not really concerned about 60mph driving. I do realize it will be turning some decent rpms at that speed. This is a good thread that got me thinking about it. But I dont think it will be any issue. Plus I didn't buy my 3/4ton for freeway driving. My 1/2 ton will take care of that.

 

[Dougnsalem]

You can adjust the vacuum modulator on your TH400 to modify the shifts a bit.

Or just floor it, until you hit cruise speed. That should harden up the shifts a bit.

Seriously though, IMHO David, you shouldn't have anything to worry about. Same with you, Jason. Jeremy, on the other hand, is just flat out screwed..... Lol

 

[Frankenchevy]

Jeremy, on the other hand, is just flat out screwed

Yes please

 

[dajn37]

As tony beats from gold rush would say. "Giver giver giver!!!!!!!!"

 

[Mandoguy]

You don't even look at the profiles before you post a reply, do you? He has a K20....

Yeah guys I’m new to these forums so cut me some slack

 

[Dougnsalem]

Yeah guys I’m new to these forums so cut me some slack

I'm not quite sure what brought that on- but to be clear; I wasn't saying anything bad or negative, about, or to you at all.