4L85E or Gear Vendors???

[ExpoMike]

Hi all,

I am building a CUCV M1010 ambulance into an offroad camping rig. I have recently put 35" tires on but with the 4.56 gears, I am still very limited in top speed and keeping the RPM's reasonable. Without a doubt I am going to need to put some sort of overdrive system into my rig.

Here's were it gets a little complicated. We do very remote camping, in many cases 50-100 miles from the nearest anything let alone repair shop. I need to have something that is about as 100% reliable as possible (and needs to stay an auto so my wife can drive if needed). I have been reading so much about both units over the last couple months. I am just as unsure today as I was when I started.

My biggest thing is reliablity and it seems each unit, people have had issues with. Here's seems to be the pros/cons from what I have found.

4L85E
Pro's: Strong, basically same ratios as current T400 with adding OD, can be tuned (depending on controller used) to meet specific needs, serviced by any GM dealer or trans shop, likely not to add any vibes to driveline, all four gears availabe in 4WD Hi/Lo range, one less item in the driveline system
Con's: Cost, more parts to install to get to work (controller, TPS, etc.), need to modify both driveshafts, some people have issues with failed units

Gear Vendors
Pro's: Can gear split, simpler install, only modify one driveshaft, can have auto or manual control, less overall cost
Con's: Can add vibes to driveline, additional lenght off transfer case, can be finicky with smooth shifting, only used in 2WD, less repair shops available, some people have had issues with failed units


I am not looking to something that is going to be towing a trailer so not worried about that but I will be spending a lot of time in the dirt where I might be crawling along at less than 20 MPH for hours on 2-3 rated (out of 5) trails.


What would you choose and why?

 

[ColoradoBill]

I would consider a 700r4. great 1st gear, and a good overdrive. less electronics then a 4L85E.

 

[ExpoMike]

Diesels eat 700's for lunch. I have put them into other projects before but would never put on in a 6800 lbs rig with a almost 10K GVW.

 

[shortbus4x4]

I have driven the older heavy diesel vehicles with both a 4L80E and a Gear Vendors. With a 4L80E your mileage should go up a little when cruising on the highway due to torque converter lockup. For your rig I would probably go with a GV unit and here is why. A 6.2 diesel isn't eactly known for its gut wrenching power. Having a GV helps split the gears keeping the 6.2 in its narrow powerband. This will really help pulling hills at speed. I wouldn't worry so much about the fact that you can use it only in two wheel drive, most of the time when you are in 4x4 you will be going slower anyway. The limited experience I have had with GV units is to keep the oil changed and use good oil, the only ones I have seen blow up failed to follow any maintenance at all. I have quite a bit of stick time in a 83 F250, 4x4 6.9 4 speed manual GV unit, that my dad used for his logging business. The GV blew up and he sent it off to get repaired, he put a stock driveline while the GV unit was getting rebuilt and we used the truck. It sucked big time pulling hills, 3rd was too high and 4th was too low so it was back and forth between the gears. Having the GV allowed us to pull hills in 3rd and over which was a lot less shifting. If you get the big sump unit and keep the oil changed on a regular basis you shouldn't have any problems. When our GV went out you could still drive, it just didn't have work anymore, no OD or gear splitting. I saw one other failed GV at a shop I worked at, truck still driveable, just no OD.

 

[BIGdaddy]

I have no knowledge of either unit, but what about this:

1. Add a turbo to the 6.2L,
2. go up to 4.10's
3. and/or up to 37-38's?

Just going up to 37-38's should lower your rpm's quite a bit, and if you find you need more power to spin the meats, I'm pretty sure there's a nice turbo/exhuast kit from banks for the 6.2L.

I'm all about keeping it simple and tuning what you have to your needs. Both drivetrain options seem like they add quite a bit of complexity but I'm sure you'll get lots of good comments from others about those.

 

[Silverado]

no vote for the NV4500 5 speed manual? Those came behind the 6.5TD's

 

[BIGdaddy]

no vote for the NV4500 5 speed manual? Those came behind the 6.5TD's

He's wanting an auto so his wife can drive it.

Can Lisa learn to drive a stick, Mike? You could tempt her with spa days or something like that..haha!


(My wife prefers auto's too, so I completely understand his reasoning, btw. )

 

[Silverado]

anyone with 2 legs can drive a hydraulic clutch

 

[chasespeed]

anyone with 2 legs can drive a hydraulic clutch

Yep. True.

BUT, I have been trying to bribe my wife to learn to drive a stick for a LONG time..... She gave it a quick go once or twice.... but, got too frustrated trying to listen to/feel the engine, etc etc etc......

Needless to say, my TRUCK is a stick.... her car is an auto.... next project MAY be an auto so she can drive if need be...

Chase

 

[ExpoMike]

Thanks for the comments so far. As for a manual, I did work at teaching her and she "could' do it in an emerency (we might be in 1st the whole time LOL) but no go for normal driving duties.

To Brian - as for the turbo, I got a Banks system sitting in the garage I picked up off Craigslist. I would be installing it already but the alternator system on the 1010 doesn't allow for this to be a bolt on. It will take a bunch of mods to get this to work. I have been forming a plan but it's low on the list at the moment. No plans to change the gearing. Already in there with a Detroit in the rear. To go to a lower gear, I have to change the carriers and such. Just not worth it and I would really need to get into the mid 3's to even make it worth wild. I think 3.73's are as low as I can go. 35's tires is my limit. Minimal lift and cutting required, unlike 37+ tires. Wife is already having issues getting into it.

Shortbus - that is some good real world info. I have been leaning to the GV for the reasons you said, the gear splitting ability. Since I will be driving thru mountain passes to get out anywhere, I think having that gear between 2nd and 3rd will really be a blessing. It is good to hear that even if it fails, I can still drive, just without the OD function. I can live with that. I just didn't want to have a problem where it breaks and now it won't move (mainly on the trail). Not many things are going to be able to get me pulled out in the middle of nowhere.

Keep the info/suggestions coming. Real world experience is definitely a plus!

Thanks guys.

 

[shortbus4x4]

It can break where it will leave you stranded, just take some wrenches to undo your rear driveline and front wheel drive it to home. My limited experience with them is that when they fail you just lose the ability of splitting gears. Try giving GV a call directly and talk to one of their rebuilders to see what usually fails, I don't think they have catastrophic failures but I could be wrong. The three or four times I called GV about tech questions they transferred me right to a actual mechanic who was very helpful in anwering my questions. When my dad got his fixed they were pretty good about it and rebuilt it for him instead of trying to sell him a new one. Lots of companies don't bother with rebuilding their product once they sell it too you but GV does. I would take the GV over the 4L80E because it does give you the ability to split gears and have OD too. You will love it so much better in the hills than the 4L80E.

 

[Chas Stricker]

I had a 6.2 and put a Bank's Turbo on it. There are three different manifolds for the turbo housing that could put it High in front, middle-ish high, and rear low. I had a 700r4 built for it and it was amazing! Many miles crawling and highway.
Chas

 

[ExpoMike]

It can break where it will leave you stranded, just take some wrenches to undo your rear driveline and front wheel drive it to home. My limited experience with them is that when they fail you just lose the ability of splitting gears. Try giving GV a call directly and talk to one of their rebuilders to see what usually fails, I don't think they have catastrophic failures but I could be wrong. The three or four times I called GV about tech questions they transferred me right to a actual mechanic who was very helpful in anwering my questions. When my dad got his fixed they were pretty good about it and rebuilt it for him instead of trying to sell him a new one. Lots of companies don't bother with rebuilding their product once they sell it too you but GV does. I would take the GV over the 4L80E because it does give you the ability to split gears and have OD too. You will love it so much better in the hills than the 4L80E.

My main breakage concern would be more with it locking up and not allowing the transfer case to rotate, hence stopping any movement. I am definitely leaning this way and because GV is local to me, I am going to swing by (hopefully tomorrow after work) and talk to them in person. Still good real world info. Thanks.

I had a 6.2 and put a Bank's Turbo on it. There are three different manifolds for the turbo housing that could put it High in front, middle-ish high, and rear low. I had a 700r4 built for it and it was amazing! Many miles crawling and highway.
Chas

That's something I have not heard about. Might be time to call Banks. I think a mid high setup would work as I think the kit I have (which is for a '83-'87) is a front high mount. I had been thinking of using a 6.5L turbo manifold and a T3-T4 adapter to use the Banks turbo. Again, this is kind of low on the list right now. Thanks for the info.

 

[bob91yj]

I've seen several GV's in different applications lose reverse completely. Owners always thought it was the transmission that was the problem. So did I the first time, pulled an Allison out of an RV, tore it down, found nothing wrong, re-installed, still no reverse. I never dreamed it was the GV, but it was. I knew what to look for after that. A buddy of mine lost reverse in his Dodge P/U.

I don't like the idea on an Expo rig because you are adding complication, and another drivetrain component that can fail.

 

[ExpoMike]

I've seen several GV's in different applications lose reverse completely. Owners always thought it was the transmission that was the problem. So did I the first time, pulled an Allison out of an RV, tore it down, found nothing wrong, re-installed, still no reverse. I never dreamed it was the GV, but it was. I knew what to look for after that. A buddy of mine lost reverse in his Dodge P/U.

I don't like the idea on an Expo rig because you are adding complication, and another drivetrain component that can fail.

Yeah, that's been my one issue with the GV. I have heard you absolutely cannot use reverse with the GV overdrive on. Something about the internal cone clutch killing itself and I guess this is not a warranty item if you do it.

As for adding complexity, trust me, adding the 4L85E adds way more items to fail (computer, TPS, sensors in trans and not including the mechanical part of the trans).

Going to see what GV has to say when I visit them today.