Gear Vendors Overdrive it is

[GPrez]

After a whole lot of research on here and deliberating I have decided to go with the Gear Vendors overdrive unit in my M1028. I figured I would post me reasoning in case others are having the same hangup.

I had narrowed my decision down to a 700r4 swap and the GV. The 4L80 and 4L60 just turned me off due to the electronics required and extra parts that would be needed. I wanted it to be simple and easy to understand.

The 700 was tempting and I had even made an offer recently to someone who was selling a 700 with transfercase out of a 86 Jimmy on CL. The seller never responded to my offer though. I calculated the cost of a used 700, having it rebuilt with good parts, and a low stall TC and the other stuff like finding the TV bracket etc. and I was getting close to $2K maybe a little less. Then factoring in the time and effort to replace the transmission and mating it to the NP208 it just seemed to get real close to the GV unit in overall cost if you factor your time and gathering all the components.

The GV unit appears to be a simple 1/2 day install and I couldn't find a bad review on them anywhere. The initial cost of the GV is a turnoff for sure. I fully intend to keep this truck a long time, but you never really know as life changes from day to day. The thing that popped into my head that really steered me to the GV was that if I ever do sell the truck I could remove the unit, install the original driveshaft and sell the truck and GV unit separately. I feel I have a better chance of recouping part of my investment this way verses the 700r4 as you wouldn't want to remove it. The initial expense of both options sold in the truck is never going to be recovered, but if sold separately might.

I ordered it today from a Speed shop in the building next to my office. It was actually less than buying from the GV website even with sales tax & shipping. I also got the satisfaction of buying from a local business. Should be here in 1 to 2-weeks and I'll post some pics of the install since I didn't see any install threads in my search.

 

[Keith_J]

The only issue I see with the GV OD is torque converter slip may increase. So while it lowers engine speed, it may not provide all the economy of a 4L80/4L60 or a NV4500 manual transmission swap.

 

[fitz]

Looking forward to see how the install goes.

 

[scottladdy]

Please keep us posted. I am contemplating the same set of questions, and have also narrowed it down to 700R4/4L60 or a GV. Very interested to see how this goes for you and what the driving experience becomes.

Please consider posting a video of driving the truck before and after the install.

Best regards ...

 

[Dave Kay]

YEAHHHHH!!!!! Woo-hoo! Awesome dude! WOW! Just got a new GV unit myself a couple weeks ago and been busy tying up a lot of loose ends (new starter, new flexplate, belts, hoses, fluid changes, total starting/charging system cleaning and inspection) and FINALLY I'm ready to do the GV install too...

My thinking is same as you; if and when time comes to sell CUCV--- the GV unit can be removed and put into whatever, with just an adapter change. Thought about 4L80 swap too but the work and expense turned me off. Also thought about going to 4.11 final on a later date, but for now would like to see how the 4.56 does... good luck and work safe!

 

[MarcusOReallyus]

So, if I understand this correctly, the GV unit replaces the tailhousing, right? So you use the same transfer case and shortened driveshaft? Or do you need to do other mods?


If the new tailhousing is longer, how does that work with the TC?



So, this basically gives you a 6 speed transmission? Shifts automatically? Or do you have to switch it manually?


Looking forward to seeing your installation pics!

 

[GPrez]

Still waiting on mine to be delivered, but it should be here soon. My understanding is you remove the current tail housing and install the GV unit which just bolts on in place of it. There is a wire harness to run to the cab with a controller that mounts to the dash. The unit can be turned on and off by the controller. It works automatically, but I believe you can control it manually as well. Shorten the driveshaft and your ready to go.

 

[GPrez]

My unit arrived on Monday and I spent a couple hours last night reading the install instructions and starting the install. It is quite simple to install.

I removed the rear driveshaft, then disconnected the speedo cable from the tail housing. Removed the 4-bolts holding the tail housing on and removed it. Clean off the old silicone on the face of the transfercase and clean it real well. There is a piece of plastic in the end of the original tail housing that needs to be removed and placed on the new tail housing. I forget what it was called in the instructions, but it fits right on the end. Lubricate the bearings inside the new tail housing with white lithium grease and put a 1/8" bead of silicone on the end of the transfercase and install the new tail housing that comes with the GV unit. They provide 4-new bolts to use and torque to 45 ft.lbs.

There is a coupler that then gets installed over the shaft going in from the end of the tail housing. This coupler needs to be shimmed. The GV unit comes with the shims to use. I only needed 3 of them. You slide the coupler on all the way and put a straight edge across the end of the tail housing with the gasket between the straight edge and the tail housing. See how many shims are required between the straight edge and the end of the coupler. remove the coupler and place the shims inside of the coupler and slide it back on. The next step is installing the actual GV unit. I would have done that last night, but I needed some trans fluid to lubricate bearings as it is installed and I had none. This whole process took about an hour. I'm digging how easy this is so far.

I'm terrible about taking pictures, but here are a few.

Old housing and driveshaft in place

New tail housing and Coupler

New tail housing in place

Coupler in place to measure for shims

Shims that go between the coupler and the shaft on the transfer case.

Extra Shims

 

[V8Astro]

Keeping an eye on this thread. I went the 4L80 route and it's been a giant PITA from the beginning...

 

[GPrez]

GV unit installed

I have about 90-minutes of time invested in this install so far. The GV unit is installed now and the speedo cable extension is installed. I'm going to go ahead and have a new driveshaft made instead of shortening my original. Will be ordering it today, so it could be a couple weeks before I get everything completed.

All I have left to do at this point is the wiring for the unit. I will tackle that this weekend if not sooner so I will be ready to go once the new driveshaft arrives. The wiring doesn't appear very difficult either.

http://i1099.photobucket.com/albums...E-888B-688D0C410D38-1406-0000028DA543065C.jpg
http://i1099.photobucket.com/albums...0-887C-A407BF2AFCA1-1406-0000028D966EB8FC.jpg
http://i1099.photobucket.com/albums...6-972C-F24E025C1BCC-1406-0000028D8F9E897A.jpg
http://i1099.photobucket.com/albums...6-AFB3-FF4CF4997DC5-1406-0000028DA0102B02.jpg
http://i1099.photobucket.com/albums...2-A829-5E8ACF695610-1406-0000028D9B06BEE8.jpg

 

[Dave Kay]

Looking good man! And I'm really liking that lift your truck sitting is on--- sure wish I had access to one!

Between my work and all the holiday activities--- STILL haven't gotten to my GV install---- but truck DID have a successful restart after months of sitting, and with fingers crossed, the brand new 28MT starter purred like a kitten.

Thanks for the photos, gives me the nice visual on how it'll look. I think the install is pretty straight forward work-wise, with the electrical being about deciding just where to mount things. Also want to get a tach installed to get some idea of before RPMs and after so may wait a bit longer yet to tackle my install.

Wondering about drive shaft situation; spent over $300 to have the original (read that bent) driveshaft done up and it's got hardly 500 miles on it. Seems to be three options: have a totally new one made; or get a used shaft from wreaking yard and have it redone; or have this one chopped and at what cost. Local driveline guy says he can't give me a quote until I bring him something.

Mind if I ask; what will your new driveshaft set up cost? PM me if you like

 

[GPrez]

I'm only guessing, but should be in the range of $250 to $300. I'll have to send them my slip yoke that came with the GV unit so they can properly balance the shaft.

I called them today and I have to use a different template to measure on than the one I used. The guy was not a big fan of the Gear Vendors being used on 4x4's. His concern was the amount of coverage on the slip yoke. They are less than a normal slip yoke apparently and he worries about there not being enough travel. If it pulls out too much he said I will get some vibrations. I'm not using mine for heavy off road use so I'm not overly concerned.

 

[MarcusOReallyus]

Great pics, GPrez!

What's the weight of that unit?

 

[Dave Kay]

I'm only guessing, but should be in the range of $250 to $300. I'll have to send them my slip yoke that came with the GV unit so they can properly balance the shaft.

I called them today and I have to use a different template to measure on than the one I used. The guy was not a big fan of the Gear Vendors being used on 4x4's. His concern was the amount of coverage on the slip yoke. They are less than a normal slip yoke apparently and he worries about there not being enough travel. If it pulls out too much he said I will get some vibrations. I'm not using mine for heavy off road use so I'm not overly concerned.

Thanks for the info.

On that slip yoke issue; is your truck suspension stock or lifted? Maybe there might be a problem there. My plans are not for rock crawling or super tough off road use either. Mostly trails and existing dirt roads, stock suspension, slightly taller tires. My idea in having GV installed is to get to the trail head within relative comfort/time/economically.

I'm no expert but I've read some things on drive-line probs and the guys I use here in SoCal come pretty highly recommended by racing people so I figure they've probably solved most any drive-line problem. These guys recommend 3/8 inch slack in slip yoke travel as a shorter/longer travel is not good. The site's address is http://www.iedls.com/ and the info I'm referring to is in PDF format. Try here. Or maybe give GV a call and see what they say. In the install instructions it gives you a number to check your slip yoke travel for measuring, don't have it right off, I'm at work. But check that out too and be sure you're measurement is within GV's specs, or you may have warranty issues if otherwise.

Good luck, keep us posted

 

[GPrez]

Great pics, GPrez!

What's the weight of that unit?

Thanks. I did not weigh it, but I would guess about 25 or 30lbs. I pulled up and down on it and it mounts very solid. There is no movement between the crossbrace and the tail. I'm considering fabbing a crossbrace anyway just for peace of mind. Update: According to the GV website 32 to 46lbs. is the weight of the units. I'm gonna guess mine is on the lighter side.

On that slip yoke issue; is your truck suspension stock or lifted?

2-inch tuff country springs in front, and 1" zero rate in the back.

 

[rsh4364]

im so glad you posted this thread,while i cant do this for my 1009 it made me go to gearvendors site, and gonna order one for my hotrodded 79 malibu ,450-475 hp.sbc th350 and 410 rear, might even be able to with a 373 or 389 gear and have 6 gears and od, should be worth a few tenths..thanks

 

[truck1]

I've been running a GV in my 1028 for about 2 years. Only way to go for the highway. I'm getting 17-20 mpg. Only problem on the install was the need to shim by 1 inch the transfer case cross member. Used flat bar cut and drilled to fit. Easy fix, but until I did this I had a bad vibration and noise. My truck has a 4" ORD lift. I shortened my driveshaft.Cost 90$-cheap fix. I leave it in manual mode and engage using the floor switch. Imortant to change the oil in the unit every 5k miles and initially after 2k or so. Great unit and easy install. Pricey but without it these trucks are not good for practical highway use. Unless you want an eventual blown motor. At 70 mph I'm revving the motor 2310 Rpm's. My 6.2 likes that.

 

[GPrez]

Good info truck 1. It's reassuring to hear from someone who has been running one. I only have a 1" zero rate in the back so my driveline angle won't be as steep as yours so I'm going to skip shimming the transfer case starting out. I also decided to go with an aluminum driveshaft to lower the weight at the slip yoke and hopefully lesson the chance of any vibration.

I sent my slip yoke out Thursday to the driveshaft fabricator. I should get the completed driveshaft in a couple weeks.

 

[MarcusOReallyus]

GPrez, who are you using for the driveshaft? DriveLine Specialist down in Lorton? Or somebody else?

I've got a dented driveshaft for a civvyChevy that needs help. Planning to make the drive over to Lorton to drop it off. There doesn't seem to be anybody closer to me.

 

[GPrez]

GPrez, who are you using for the driveshaft? DriveLine Specialist down in Lorton? Or somebody else?.

I couldn't find anyone local to make me one from scratch, so I went with someone I found online. Driveshaft Specialist of Texas in San Antonio. They were very helpful when I called and were familiar with what I was trying to do.