Gear Vendors install on a 72 K2500 Things I learned

[conoco]

Figured I would share my experience with the Gear Vendors install on my 72 k2500. There was a lot I learned and even more I took my time on to make sure things were good. This is just a summary for those that might encounter this in the future. Hope everyone is well.

Do's
1) Before you touch anything take "MEASUREMENTS" of your drive shaft. You will need to know the pinion yoke degrees from the Transfer case and also the rear end. ( This is important) you will also need the drive line degree/ angle. You have to have these for reference to compare the new or cut drive shaft too MANUFATURER SPECS SAY THAT THEY BE WITHIN 3° there are plenty of resources to read on this topic. Or you could just ride the lightening and hope for the best LOL. ( There are a lot of great resources online that will help you find your angles, use them if needed)

2) For me I had a small leak coming from my NP205 so I decided to just pull it, get it on the bench and change the gaskets. Once I got it out that snow balled into me completely disassembling it so I could make sure the bearings and gears where good ( They looked great) For those that have not pulled a transfer case by yourself you will have lots of fun!! But since you got it out I would recommend spending the extra couple hours to go through it, clean it and paint it. ( Your gonna have a shiny new gear vendors unit so you might as well have a matching transfer case

3) Back to the transfer case. Since you have it out I CAN NOT STRESS ENOUGH THAT IT WOULD BE A GREAT TIME TO ALSO PULL OUT THE TRANSFER CASE TO TRANSMISSION ADAPTER AND REPLACE THE 2 SEALS AND O-RING. These seals and o ring are prone to fail leaking fluid into the transfer case. Some might use ATF for the transfer case also so you might not notice. But those that use gear oil don't want the mix of the ATF. these seals are super easy to change and there is no better time!! Also, might as well paint that to to match the transfer case!

4) The new Gear Vendors unit come with a MSD control box. This replaced the old style control box that they use to send with the GV Unit. These are much more stream line. Follow the directions to a T and you will have no problems with he electrical portion of the install.

5) For those that do not have a 4x4 indicator light. My 72 np205 does not have a light and I believe this wasn't even an option until the late 70s. With this said it is very important that you make sure if anyone else is driving your truck other than you that you disconnect the auto feature on the GV unit. If your gear vendors engages while in 4x4, well you will very much regret it. It will engage in 4x4 if you have not disconnected the auto feature. There is electrical wires from the GV unit that should be hooked up to the 4x4 indicator on most trucks "Safety feature" that automatically disables the system when 4x4 is engaged. For me I am in Alaska and use 4x4 often, however, I am the only one that drives my truck. Just for safety I connected the Auto wires to quick connects. If someone else does drive my truck in the winter I can just disable this feature very easily. If I forget to do that and they throw it is 4x4, I will have the same results as I mentioned above. I spoke to the GV techs for about a half hour and they told me to just do away with the auto feature all together for safety and just run in manual. I really want the auto feature in summer time on long trips and I think I am smart enough and know enough about my truck to make sure is is disabled if I need it to.

Last thing I learned.
When you take your drive line off "Wire wheel" it and clean it before you take it to get shortened. If you do this the shop will more than likely paint it for FREE!. I cleaned mine and took the old u-joints of and then degreased it. Surprisingly when I picked it up they had painted it ( no charge) the guy told me I already spent the time cleaning it and all he had to do was spray it and it looks awesome. I also had them throw in Spice LIFE u-joints ( Non-Greaseable for strength) at the same time because they needed to be replaced anyway. they are a little more expensive but well worth it.

If you have a slide yoke on your drive shaft you can still use this, but you will need to have GV send you the fixed yoke for the GV unit and not the slip yoke. Instructions call for 5/8 play in the slip yoke that goes to the GV unit and ties into the drive shaft, however this is for a solid drive shaft and not and slip shaft. Just something to consider. I am about a month out from finally testing this thing out, just welding the mounts for the leather seats on a 2010 Tahoe and then will be all set.

I installed the "Red and Green" indicator lights to the left of my radio and they turned out pretty slick looking.

Hope this can help someone. Its a big purchase and a lot more than just throwing a 700r4 in. I love my th350 and wanted to keep the stock components plus being able to split gears while towing and going through the mountains here in Alaska to my favorite fishing hole is worth way more than just slapping in a r4. Good luck and be safe!

[BigBird05]

After looking at your pictures of the Gear Venders unit, it looks remarkably similar to the one we made in GM experimental in the late 70's. Ours worked well when you ingauged it, but we had trouble with disengaging it. Any way I think it was used to test the theory of an over drive transmission.

[conoco]

Originally Posted by BigBird05

After looking at your pictures of the Gear Venders unit, it looks remarkably similar to the one we made in GM experimental in the late 70's. Ours worked well when you ingauged it, but we had trouble with disengaging it. Any way I think it was used to test the theory of an over drive transmission.

Fun Fact:
All GM Callaway Twin Turbo Corvettes with automatics came with a TH400 and GEAR VENDORS instead of the 700r4 which was the base Corvette trans.

I did a lot of research and reached out to a lot of people that have these units before I made this purchase. I am confident that it will be an excellent addition based on those conversations! Only time will tell. As long as I am not at 3500 rpms at 65mph anymore I will say its a success

[HO455]

Thanks for posting your experiences.
It good to hear they have finally moved on from their 1970's vintage controller. Hopefully the new one is not as susceptible to stray electronic signals or noise as the old one. The MSD unit is a fairly recent change as they made no mention of it during our conversations in early 2020. Do you have any photos of the new MSD unit?

[chewychevy67]

Yes I would like photos as well. I have my unit on my transmission but haven't started the wiring yet. If it's improved I may Try to get that set up myself

[bry593]

Tiny sump on that overdrive. How often does GV recommend you change the oil?

[conoco]

Originally Posted by HO455

Thanks for posting your experiences.
It good to hear they have finally moved on from their 1970's vintage controller. Hopefully the new one is not as susceptible to stray electronic signals or noise as the old one. The MSD unit is a fairly recent change as they made no mention of it during our conversations in early 2020. Do you have any photos of the new MSD unit?

I had no idea I was getting the new controller. I was expecting that big white control unit. I was surprised when I opened everything up and got this one. I thought they had sent me the wrong unit. I am up on the Oil fields of Alaska and wont fly home for 2 more weeks. I will look through my camera roll and see if I have any. If not I will update this post as soon as I get home.

I will say its pretty slick looking. I installed mine away from most any wires ( At least where I could) I will update soon.

[conoco]

Originally Posted by chewychevy67

Yes I would like photos as well. I have my unit on my transmission but haven't started the wiring yet. If it's improved I may Try to get that set up myself

I don't have a picture but I do have the instructions that I took pictures of and it has the new control unit on the top left. It looks just like this and is black. Its pretty small and easy to tuck away.

It also came with the headlight switch for using manual mode, and it came with another switch that is attached to the green and red LED lights with is how you put the unit into manual or Auto.

I will still take pics when I get home but this will have to do for now. I believe it just came out not to long ago to address some of the problems with the old unit and just because it needed to be updated.

[conoco]

Originally Posted by bry593

Tiny sump on that overdrive. How often does GV recommend you change the oil?

Every 5,000 miles

[D.B]

Hey Conoco, I installed a GV in my 72 C20 about 5-6 yrs ago. I am running a 511 big block , T400 trans and a 4.10 gears with 31" tires. I hated getting up on the highways because of the rpms the engine would turn. At 50 mph it would turn about 3100 rpms. And now with the GV and 33" tires I can run 65 mph at about 2300-2500 rpms. I have not learned to split shift but I did not buy the GV for that purpose. You are going to like your GV.

[conoco]

Originally Posted by D.B

Hey Conoco, I installed a GV in my 72 C20 about 5-6 yrs ago. I am running a 511 big block , T400 trans and a 4.10 gears with 31" tires. I hated getting up on the highways because of the rpms the engine would turn. At 50 mph it would turn about 3100 rpms. And now with the GV and 33" tires I can run 65 mph at about 2300-2500 rpms. I have not learned to split shift but I did not buy the GV for that purpose. You are going to like your GV.

I can't tell you how happy I am to hear you say that. I take my truck on long fishing trips here in Alaska and before this unit I am at 3500 rpms at 60-65mph. It is so loud in my truck that I have to yell to talk to my kids lol. I was honestly going to consider it a success if I could just get it to 2600. Everything I have read and those that I talked to seem to thing 2200-2500 should be expected. I will be very happy with that. I have a 4" lift with 35s and 4.11s. Thanks for sharing that!

[BigBird05]

Wow, after looking up Gear Venders on the web site I guess I'll be looking for 700 R4.

[conoco]

Originally Posted by BigBird05

Wow, after looking up Gear Venders on the web site I guess I'll be looking for 700 R4.

Most people do!! They cant afford the GV unit, it is an investment. I would take my th350 over the r4 any day. However, I do pull my camper and trailers up mountain roads all summer. Being able to split gears is worth way more to me than the money saved from putting in the weaker r4. Then again, the r4 will work just fine depending on what the truck is used for. I wanted to stay stock and have a beefy strong transmission. But I get what you are saying!

[un4gvn!]

I also installed a brand new GearVendor in my 69 big block truck with a T400. The same reason as you all, high rpm's at 60-65 and getting real bad gas mileage. I also race my truck and I was talking to GearVendor on the phone. They informed me to use the unit when I race and let them know how much I enjoyed it. Can't wait for all this snow to melt and the drag strip to open up. I look forward to it.

[jocko]

Originally Posted by conoco

I can't tell you how happy I am to hear you say that. I take my truck on long fishing trips here in Alaska and before this unit I am at 3500 rpms at 60-65mph. It is so loud in my truck that I have to yell to talk to my kids lol. I was honestly going to consider it a success if I could just get it to 2600. Everything I have read and those that I talked to seem to thing 2200-2500 should be expected. I will be very happy with that. I have a 4" lift with 35s and 4.11s. Thanks for sharing that!

Your before and after RPM snapshots at various highway speeds are below (can be more exact if you want to measure actual tire diameter and post it). The 35s help your highway rpm about as much as your GV unit - together, you'll have a very nice quiet highway ride . If you want to cross-check once you start driving, make sure to use a GPS for the correct speed when you check RPMs - with 35s the speedo is not accurate unless you've monkeyed with speedo gears to get it close to correct, but a GPS will still be the most accurate reading.

With 35s and 4.11 gears:
(without GV/with GV)
at 55 mph - 2170 rpm/1693 rpm
at 65 mph - 2565 rpm/2000 rpm
at 75 mph - 2959 rpm/2308 rpm

Thanks for the detailed write up and tips, always great to see what others encounter when they do these types of upgrades. I've toyed with the idea on my K20, but will be w while before I get around to it(!)

[conoco]

Originally Posted by un4gvn!

I also installed a brand new GearVendor in my 69 big block truck with a T400. The same reason as you all, high rpm's at 60-65 and getting real bad gas mileage. I also race my truck and I was talking to GearVendor on the phone. They informed me to use the unit when I race and let them know how much I enjoyed it. Can't wait for all this snow to melt and the drag strip to open up. I look forward to it.

Really hoping with time I can get the manual mode figured out. I have read everything I possible can on the GV unit multiple times, it's time to do it now have fun at the strip brother. Let me know on this post how it went for you!!

[HO455]

Originally Posted by BigBird05

Wow, after looking up Gear Venders on the web site I guess I'll be looking for 700 R4.

They come up for sale used all the time. I've bought 3 of them over the years never paying more than $1300 for one. The one I put in my Burban was $600 complete with a TH350.

[HO455]

Originally Posted by conoco

I don't have a picture but I do have the instructions that I took pictures of and it has the new control unit on the top left. It looks just like this and is black. Its pretty small and easy to tuck away.

It also came with the headlight switch for using manual mode, and it came with another switch that is attached to the green and red LED lights with is how you put the unit into manual or Auto.

I will still take pics when I get home but this will have to do for now. I believe it just came out not to long ago to address some of the problems with the old unit and just because it needed to be updated.

Thanks for posting.

[KevinK7]

Thanks for posting in the GV.
The '69 C20 I picked up has an older GV unit in it. I did sell this truck to my brother (since two 68's is enough lol) but I contemplated keeping the GV, but let it go.
Somewhat curious about it, and glad to see someone posting on it

[conoco]

Originally Posted by HO455

They come up for sale used all the time. I've bought 3 of them over the years never paying more than $1300 for one. The one I put in my Burban was $600 complete with a TH350.

I wish they came up used all the time here in Alaska LOL I see them for sale in the states but the shipping price is ridiculous, then add in the cost of the adapter for whatever its going in and spending the extra money for a new one is almost cheaper, or at least the peace of mind having the warranty is I wish I lived in the states sometime, well until I go there! I would have a yard filled with 72 gmc's!! I was lucky to find mine. Stay well brother!

[conoco]

Originally Posted by jocko

Your before and after RPM snapshots at various highway speeds are below (can be more exact if you want to measure actual tire diameter and post it). The 35s help your highway rpm about as much as your GV unit - together, you'll have a very nice quiet highway ride . If you want to cross-check once you start driving, make sure to use a GPS for the correct speed when you check RPMs - with 35s the speedo is not accurate unless you've monkeyed with speedo gears to get it close to correct, but a GPS will still be the most accurate reading.

With 35s and 4.11 gears:
(without GV/with GV)
at 55 mph - 2170 rpm/1693 rpm
at 65 mph - 2565 rpm/2000 rpm
at 75 mph - 2959 rpm/2308 rpm

Thanks for the detailed write up and tips, always great to see what others encounter when they do these types of upgrades. I've toyed with the idea on my K20, but will be w while before I get around to it(!)

Thanks Jocko!! That's great information, Once I get her out on the road I will surly map it out. I also have the Progression distributor in my truck and that thing is awesome. Shows my timing in "real time " and I am able to change it on the fly. But the graph shows my RPM range through everything, pretty slick and I got about 2 months of driving into it before I parked it for the winter! Really excited to get her out! Just have to get my seats mounted! Stay well brother!

[davischevy]

I thought when I put the GV in my 71 K20 I would learn to split shift it, but it works so good in automatic I just leave it there and drive it.