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Six speed?

Jason63

Jason63

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North Idaho
Hey I was wondering how hard it is to put a six speed allison in my 95 gmc k2500? I need to lower my rpms. Lot of freeway driving, I'm at 2800 at 70, I would like to be at around 1800-2000 at that speed. Would it be cheaper to change rearend and I dunno is it a gearbox on these or does the tranny and transfer case determine gear ratio? I just need to do it the cheapest way, without jacking it up with big tires, thanks
 
I can't help you with the trans. swap but a Gear Vendors overdrive would work. They aren't cheap but I don't think a swap would be either.
 
need to buy tranny, standalone computer, adapters, shortened driveshaft, torque converter, and a new tranny crossmember. i would go to a taller gear ratio. it wont be cheap but its a lot cheaper than a allision swap
 
With the nv4500 and 3.42 gears and 32-33" tall tires will put you around 2000rpm at 70mph

My 3.42 gears are semi-floating, so might be whole axle swap.

I think you can find 3.42s with worm gears too
 
Jason63 said:
Hey I was wondering how hard it is to put a six speed allison in my 95 gmc k2500? I need to lower my rpms. Lot of freeway driving, I'm at 2800 at 70, I would like to be at around 1800-2000 at that speed. Would it be cheaper to change rearend and I dunno is it a gearbox on these or does the tranny and transfer case determine gear ratio? I just need to do it the cheapest way, without jacking it up with big tires, thanks
Click to expand...
Are you positive your tach is right? You may have the wrong alternater pulley.
Run your VIN on this to tell what ratio axle you have http://www.compnine.com/vid.php
 
It depends what the tire size is, shorter tires will give higher RPMs. Taller tires lower RPM. The nv4500 final ratio is also slightly lower than the 4L80E even though it has a 5th gear.
 
NVW said:
Good catch, with 4.10's it should be about 2500 rpm at 70 mph
Click to expand...

This is excactly what mine reads with 255/85 r 16 tires and 4:10s

I think but not 100% the nv5600 will bolt in where the nv 4500 was but I dont think the 5600 overdrive is much higher than 4500.

The gearvenders overdrive would be awsome to have, but if its a 4x4 I've heard they can be a real PITA on them.
 
625fireman said:
This is excactly what mine reads with 255/85 r 16 tires and 4:10s

I think but not 100% the nv5600 will bolt in where the nv 4500 was but I dont think the 5600 overdrive is much higher than 4500.

The gearvenders overdrive would be awsome to have, but if its a 4x4 I've heard they can be a real PITA on them.
Click to expand...

The 2 overdrives of these trans are almost the same. The 5600 is just a closer ratio box. Also the 5600 came behind the CUMMINS not the GM, and the CUMMINS version used a different bolt pattern on the front IIRC.
 
Didn't the NV5600 come behind the d-max? I would like a 5 or 6 speed with closer ratios (3rd-4th) than the NV4500.
 
Mikey von said:
Didn't the NV5600 come behind the d-max? I would like a 5 or 6 speed with closer ratios (3rd-4th) than the NV4500.
Click to expand...

Nope, it was the zf6 behind the dmax. This swap is doable since the bell housing pattern will match up but the zf was a rare option and if you find one, it will most likely be high dollar.
 
bk95td said:
Are you positive your tach is right? You may have the wrong alternater pulley.
Run your VIN on this to tell what ratio axle you have http://www.compnine.com/vid.php
Click to expand...

Ya got me all excited for nothing. Went there with the intent of decoding my vin, and got a page that reads: These types of announcements don't come easy, but effective immediately Comp Nine will be closing its doors permanently.
Thank you to everyone that helped keep the site going and for allowing Comp Nine to serve the community for so many years.

Please contact [email protected] if you have any immediate concerns.
 
Jason63 said:
That's cool thx, I'll just get a new nv4500 and gear swap I guess
Click to expand...

Your thoughts may be different, but this is how I think. Wouldn't it be cheaper to just rebuild your 4500, than to buy a new one? This IS my first diesel, and my first "big" truck, but the way I think, for the cost of a new 4500, I could probably do a complete rebuild of my old one, maybe incorporate a couple of improvements (if there are any), change the clutch/pp/brg while I am in there...

I know that right now, my clutch/transmission has an issue. I think there might be a synchro issue, since I have to play with the gears to get it into 2nd, while upshifting, etc. I actually think it is more of a clutch issue though, since when I put it in gear, it wants to creep on me, and 2-3, 3-4, and 4-5 shifts are sometimes a little more effort than they should be. The clutch does not slip, so I am thinking maybe a problem with the PP... maybe a problem on one side, causing it to not operate properly. If I have to pull the tranny, I will do everything I can find that needs to be done while it is out, because there will never be a better time to do those things.

Speaking of trannies, what lube is in the NV4500, and would a synthetic alternative be effective?
 
normburns said:
Your thoughts may be different, but this is how I think. Wouldn't it be cheaper to just rebuild your 4500, than to buy a new one? This IS my first diesel, and my first "big" truck, but the way I think, for the cost of a new 4500, I could probably do a complete rebuild of my old one, maybe incorporate a couple of improvements (if there are any), change the clutch/pp/brg while I am in there...

I know that right now, my clutch/transmission has an issue. I think there might be a synchro issue, since I have to play with the gears to get it into 2nd, while upshifting, etc. I actually think it is more of a clutch issue though, since when I put it in gear, it wants to creep on me, and 2-3, 3-4, and 4-5 shifts are sometimes a little more effort than they should be. The clutch does not slip, so I am thinking maybe a problem with the PP... maybe a problem on one side, causing it to not operate properly. If I have to pull the tranny, I will do everything I can find that needs to be done while it is out, because there will never be a better time to do those things.

Speaking of trannies, what lube is in the NV4500, and would a synthetic alternative be effective?
Click to expand...

x2 on having the trans rebuilt. Guy down the road from me will do a full rebuild for $1200. Hell of alot cheaper than buying a new one all together.

normburns.....Check your clutch fluid. Being low obvoiusly causes some problems, but also look for thick black coloring. This can indicate failure of the master cylinder. A bad slave could cause some similar issues as well.

As for the origonal poster...I would think a gear ratio change would be your easiest and cheapest option. The aftermarket overdrive kits are nice (i plan on installing one someday down the road) but they are very pricey. Im running 3.73s and I still find myself wanting another gear, or a taller 5th gear, so id be looking at swapping to 3.42's if I were you.

I am curious to see if anyone actually has done a ZF swap in one of these trucks....

-Nick
 
normburns said:
Your thoughts may be different, but this is how I think. Wouldn't it be cheaper to just rebuild your 4500, than to buy a new one? This IS my first diesel, and my first "big" truck, but the way I think, for the cost of a new 4500, I could probably do a complete rebuild of my old one, maybe incorporate a couple of improvements (if there are any), change the clutch/pp/brg while I am in there...

I know that right now, my clutch/transmission has an issue. I think there might be a synchro issue, since I have to play with the gears to get it into 2nd, while upshifting, etc. I actually think it is more of a clutch issue though, since when I put it in gear, it wants to creep on me, and 2-3, 3-4, and 4-5 shifts are sometimes a little more effort than they should be. The clutch does not slip, so I am thinking maybe a problem with the PP... maybe a problem on one side, causing it to not operate properly. If I have to pull the tranny, I will do everything I can find that needs to be done while it is out, because there will never be a better time to do those things.

Speaking of trannies, what lube is in the NV4500, and would a synthetic alternative be effective?
Click to expand...
it might be better to start a new post. this one is old and your q's might be missed.
 
since it has been revived haha.

the Final overdrive ratio between the 4L80E, nv4500, nv5600, and zf 6 are all very close to each other. the difference between the manuals is the 6 speed has better ratios from 1st to their 5th (1:1). Overdrive between all 3 is about the same.

Only way to get more out of the overdrive is to either regear your axles, or install a add-on overdrive unit such as a gear vendors.
 
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