NV3500 Trany...Good?...Ratios?...

[lts70]

I have 320+hp 327 in my 70 Chevy SWB. I replaced the stock transmission with a NV3500 5 speed out of a 92 Chevy ½ ton truck (got for free out of a 600 org. mile wrecked truck). I looked every where for gear ratios and final found these on an S-10 forum. Does any one know what 5th gear ratio I would have? They had 3 different options on their site.

1 - 4.02
2 - 2.32
3 - 1.40
4 - 1.00
5 - 0.83 or .78 or .73 ?
R - 3.74

I have the stock posi-track rear-end still in the truck. Does any one know what rear-end gearing a 1970 6 lug SWB with posi from the factory would have had?

My rear tires are BFGR 285 70 R15.

I am trying to figure out if this is a good combo for my truck. If it is I want to purchase a speedo conversion box to convert the electrical signal to run my mechanical speedo. I just don’t won’t to throw $300+ dollars at something I won’t be happy with in the long run. Or is it possible to easily put a speedo gear in the trany?

So my questions are:

1) What would be my 5th gear ratio?
2) What gear ratio would my differential be?
3) Is this a good set up for my truck?
4) Is this a good trany?
5) Best way to convert to mechanical Speedo?

[Longhorn Man]

To guess what gears you have... we need to know the eng/tranny combo it had originally, and we also need to know if it is a 10 or a 20 series truck.

[Palf70Step]

3500 is a good tranny, and If I remember the NV3500 had a .73 5th.

Far as your rear end gears, like Andy mentioned, we would need to know the trucks original configuration. You could also check the glove box label, since posi's were only an option as far as I can remember.

[lts70]

It is a c-10. I dont know what trany it had by name but it was a 4 speed with first being a granny low and the reverse was on the right side. I dont know if it was original to the truck but it had a 307 when I got it. There is no glovebox decal.

[Longhorn Man]

that woulda come with a 3.07 gear... not a great gear for an overdrive. You can try it, some ppl have and came out ahead. But most will tell you the RPMs will be too low, and MPG can even get worse.

[lts70]

Thanks guys, it is good to know that it is a strong tranny and what Ratios I have.

It would be nice to have the overdrive a little lower but because Utah driver are known for there speeding, most of the time I can use it to stay up with traffic and not be ran over. On my commute to work and back I am usually in 5th gear at 2500 RPM. I think it puts me between 75 and 80 MPH.

Right after I put the transmission in I got pulled over in Idaho for going 89 MPH and had know idea I was going that fast (cop didn’t buy it). I believe I was running at 2800 or 2900 RPM then. It is weird to go 90 down the highway in one of these old trucks and have it so smooth and not feel like your motor is going to jump out of the engine bay and run off. And the Gas Mileage is a great bonus.

So I guess now my only question is how to run my mechanical speedometer off of the electronic signal?

There is a product called the cable-X that is a conversion but has any one here used it and know how it performs? I also found a Terf Inc. that has a product called the Speed Changer Mechanical which he claims will be better that the cable-X because it does not have any initial delay.

Then there is cracking the case and putting gears in. Does any one know if that is possible with this transmission? How hard it would be to do it if possible or how much money it would cost?

I am just trying to size up my options before I jump into it. Thanks guys for all of the help. I know how you guys like pictures so I will try to attach the only one I have here at work that has any thing to do with this post. It should show my shifter knob.

[elf w/capital T]

Holy smokes I want that center seat!! What did you find that setup outbox??

[WIDESIDE72]

Having the "right" rear gears ratio with a manual of trans is not as critical as it is with an auto trans. Too high if a gear with an auto causes the trans to hunt back and forth when encountering even small hills, which results in heat. With a manual trans, you will know to shift down to fourth if experiencing hills.

As for a signal converter, you're on the right track. I believe last month's issue of car craft did a story on these. I don't ha e any personal experience but there are also GPS Speedos.

Be careful "power shifting" that nv3500. You are right on the edge as far as the torque you're putting out. The nv3500 isn't as heavy duty as an nv4500.

[hamjet]

http://en.wikipedia.org/wiki/New_Ven...0_transmission A little reading....

[Gimme Jimmy]

If you want to use an Electronic speedo with the NV3500 or 4500 there is an article I found to set up a '90 to '95 GM DRAC or VSSB speed buffer
to match Tire Sizes and Rear Axle Ratios to an aftermarket or oem electronic speedo.
This is not an adaptor for an oem mechanical speedometer.
http.//www.tbichips.com/drac.
This process requires some electronic skill as some desoldering, soldering and wiring techniques are used. Basically all you need is the sender (attached to the trans), a 90 to 92 GM DRAC or VSSB (vehicle speed buffer with harness plug) (cheap from most junkyards), 2 4pin dip switches, some wire and an electronic speedometer.
I used this lashup when I installed an NV4500 in my '71 GMC, and it works great!

[Bigdav160]

This thread was brought back from the dead because of a comment on the seat.

Low back, 1980's pattern.........perhaps out of a Topkick or Kodiak?

[hamjet]

WOW! My bad! I never looked at the dates......

[elf w/capital T]

Originally Posted by Bigdav160

This thread was brought back from the dead because of a comment on the seat.

Low back, 1980's pattern.........perhaps out of a Topkick or Kodiak?

Ha! Yes I get side tracked, but thanks!