5 Speed Owners

[BoatDriver]

Replaced the NV 4500 in my 1994 K2500. The truck has 4.10: 1 gearing.
It's been 5 months since I've driven the truck, I thought that at 55 mph, the engine was turning about 1900 rpm. Now my memory isn't what it used to be, but the engine is turning at around 2250 rpm at 55rpm. Can anyone confirm this?

[joed]

My truck, with 3.73 gears, runs about 1800 rpm at 60 mph.

Have you changed the alternator lately as a different (incorrect) size pulley can affect the tach?

I suppose it's also possible the older NV4500s had a higher OD gear. Not sure on that?

Joe.

[Hubert]

I get a little under 1700 or there about rpm in 5th 55 mph 3.73 gearing 265/75 tires.

According to quad4x4.com 5th gear is 0.75:1 ratio so you can do the math if you want to mathematically check speedo/alternator accuracy.

They state there were 1st gear and reverse ratio changes but I did not see 5th gear ratio change.

[kaylabryn]

Using math with 245/75/16, 4.10 gears and .75 od ratio you should be turning 1866rpm. I second the alternator, check there first.

[poolmike]

Maybe the replacement trans is for a gasser. Check your part numbers.

www.nv4500.com

[BoatDriver]

I never went near the alternator. Called rebuilder, "We install the updated fourth gear." By updated he means a different gear ratio for the fourth gear. Now I get to replace the new trans, again!

[kaylabryn]

4th gear does not change your final 5th gear ratio. 5th gear is in the back it is the one that gets destroyed when the infamous nut backs off. All of the NV4500 had a 5th gear ratio of .73:1 no matter if it was the Dodge or Chevy design. Only the first gear ratio changed. Some after markets seem to change the other ratios to accommodate certain vehicle applications but I have never seen 5th change. I would check things real close before droping that trans out again(no fun).

[JohnC]

4th is direct, hard to change... They must have meant 5th.

Measure the diameter of your alternator pulley. Should be (IIRC) 2 9/16"

[BoatDriver]

Look at the shifter knob, I mean fourth gear.
Last night I wrote down the rpm at indicated mph.
3,000 rpm at 75 mph.
Have you ever heard a 6.5 at 3,000 rpm on cruise?
Not something you'll forget soon.
Yeh, someone must have changed the alt. pully when I wasn't looking.

[JohnC]

Look at the shifter knob, I mean fourth gear.


Sorry, can't see it from here. And I sold mine 2 years ago. Never looked at the knob anyhow. What I meant was 4th of the 5 ratios available in the trans, what ever you choose to call them. You titled the thread "5 speed owners" so I figured you were talking about a trans where the top gear was called 5th.


So, let's look at this from a different angle. Assume 245/75-16 tires, 4.10 rear and direct drive (4th in a 5 speed or 3rd in a 4 speed with LL). At 75 mph you should be doing 3392 RPM. Now shift up one gear. If you're doing 3000, your ratio now is about .885:1, not much of an overdrive. With the .73 OD ratio, you should be doing 2476 at 75 mph. Like I said before, direct is hard to screw up, so if your rpm is off in direct (not 3392), you need to look somewhere else.

If you don't like the noise, try 60 mph. Your RPM in direct should be 2714.

Maybe someone snuck in and changed your 4.10 for a 4.88 while you weren't looking... :D