97 12v Cummins speed upgrade

[Christopher P]

Hey guys, I have a 97 12v 3500 I’m afraid to upgrade the engine on because it has such a low top speed. It has a 6 speed manual and 4.10 rear.. The truck will only do about 85 mph as it sits. What are some possible ways to up the top speed on a truck like this.

 

[SAndreasen]

Do you really need a one truck to go over 85? Maybe a Honda Accord would be a better option ? I have a 5 stage edge juice with attitude and 50 hp injectors it’ll go a bit faster than 85 but I never run above that anyway

 

[Christopher P]

Do you really need a one truck to go over 85? Maybe a Honda Accord would be a better option ? I have a 5 stage edge juice with attitude and 50 hp injectors it’ll go a bit faster than 85 but I never run above that anyway

Well, I’m out in ole Nevada with wide open stretches of road 100’s miles long. A lot of times in my other newer truck I find myself doing well over 100. But I love the old 12v so much and would love to daily it but 85 at redline just doesn’t cut it. The truck is a little over stock hp.

 

[SAndreasen]

More horsepower won’t hurt it . But getting caught going that much over the speed limit sure will

 

[promisedland]

spicerparts.com/calculators/transmission-ratio-rpm-calculator (copy & paste)
Do some math & see for yourself.
2wd?

 

[Thomas (Steve) Dixon]

What promisedlandorganicfarmer said. There are also other calculators that will do the same thing on the internet. After that you can determine what changes would be best (most economical?) for you. Another option would be to add a separate OD unit.

Steve

 

[Bill Lins]

You could either change the rear axle to something a bit more highway-friendly or add an overdrive unit. The axle swap would probably be cheaper.

 

[SAndreasen]

I have 3.42 gears and they are perfect for me . You could always go up a couple tire sizes to that helps a lot

 

[Cummins12V98]

I have 3.42 gears and they are perfect for me . You could always go up a couple tire sizes to that helps a lot

less expensive especially if ya need tires

 

[Thomas (Steve) Dixon]

I have 3.42 gears and they are perfect for me . You could always go up a couple tire sizes to that helps a lot

Just curious, but did your truck come with the 3.42s, or were they added later? I was under the impression that the only choices were 3.54 or 4.10, but if 3.42s were also available it would give me another source if I decide to change mine.

Thanks,

Steve

 

[Signal73]

4K GSK and a set of 60lb valve springs are the cheapest options

 

[SAndreasen]

Just curious, but did your truck come with the 3.42s, or were they added later? I was under the impression that the only choices were 3.54 or 4.10, but if 3.42s were also available it would give me another source if I decide to change mine.
They were on the truck when I bought it used. If Your are a single wheel truck I’d go up to 285/75/16 or even a 305 size tire
Thanks,

Steve

 

[Thomas (Steve) Dixon]

Thanks, I think 3.42 would be perfect too. I just bought new 285/75R 16 tires. Perhaps I'll try 305s next time.

Honestly, it may be all right anyway. I just got the truck and on it's first fill up, after a little better than 500 miles, it only got 17 mpg. I was expecting more. Next was a trip of nearly 1700 miles where it got 20.7 Both were empty. I usually run around 70. My concern is mpg, the thing goes plenty fast for me, but bigger tires would lower rpm which, in my case, would probably provide a few more mpg.

The previous owner had a Banks PowerPack put on it. The brochure says it increases mileage, but I'm not convinced. It does go up hills all right though.

Thanks again,

Steve

 

[SAndreasen]

I had a 93.5 build date 94 one ton regular cab dually flatbed and that’s what mileage it was getting 17/ 17.5 That’s pretty good no matter what anybody says especially for a 4.5 ton truck there’s only so much you can expect

 

[GrantP]

3k GSK, #6 plate, pyrometer and enjoy.

 

[NIsaacs]

I have 3.42 gears and they are perfect for me .

Are you sure? That does not appear to be a Dana 70/80 ratio.

 

[SAndreasen]

Are you sure? That does not appear to be a Dana 70/80 ratio.

I always get them mixed up I’ll Have to see if one of the tags is still on

 

[SAndreasen]

In five early 98.5 build date model 99 trucks and one gen one I have never ever had to do anything to a rear ended but change oil and pinion seals

 

[Bob4x4]

2nd gens only came from the factory with 3.54 or 4.10

 

[BigPapa]

And, I can’t remember, is the D80 carrier different for the 3.54 and the 4.10? I know there’s a break.