CUCV Needs OD

[CUCV2]

Going closer to the minimum speed on the highway rather than the speed limit has worn out its novelty. After researching it, it seems like the best way to add a gear is the 4L80E. I found a donor tranny that was rebuilt 5K miles ago by Jasper out of a 93 GMC K2500. Issues that I am aware of are:

1- Mods must be made for the computer controls
2- Shifter may have to be modified
3- TC will need to be converted to the passenger side

For issue #1, there is a full manual valve body option by transgo.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=TRG%2D4L80E%2DS&N=700+400214+115&autoview=sku

For issue #2, there is a floor shifter available by Lokar.
http://store.summitracing.com/partd...-ATS64L80R2&N=700+4294822068+115&autoview=sku

For issue #3, Kert at DIY4X.com is the man. He is working on a clocking ring that will work with the current CUCV TC and the NP241 (d-side) adapter to actually clock it over to the p-side and up some. It is not the full clocking like his other rings as I understand it but a happy medium of sorts because there are only so many ways to make this arrangement work. The clocking amount should be ideal for this situation because this truck is a DD and the plan is to keep this tranny swap as simple as possible.

My questions are;

A) Is there anything I am overlooking?
B) Does this plan have merit?
C) Are there other options that may work better?

Thanks in advance.

 

[BKinzey]

Look at the 700r4 tranny as an option.

 

[Hogback Fabrication]

Gas and diesel transmissions use different torque converters.

You didn't say how much you were paying for the transmission, FMVB, shifter, etc. but you may be better off going to higher ratio gears.

You could burn a lot of diesel for the cost of this swap. Plus the 4.56 gears that are in there are probably worth a bit too.

 

[CUCV2]

The 700R4 is a legitimate option. The 4L80E just seems like the better choice. This is a parts hauler, semi-DD, and tow rig. The 4L80E is better suited to these needs from what I can tell.

The decision for the 4L80E was made with the factor that if the truck can be made more driveable then I wouldn't need a normal DD. The gas mileage savings alone should help to pay for the tranny the way prices are. I like the truck a lot and have driven it a year the way it is now and it is time for a change. The rpms at highway speeds are one of the few drawbacks, I have with the truck. It does seem to need the lower gears though since the 6.2 is no powerhouse.

Thanks for the suggestions so far. They were both good ideas. Are there ways to put the 4L80E in for less $ ?

 

[BKinzey]

Well, money is often a factor but your reasoning is good.

Sorry I can't help with how

 

[dyeager535]

I would think looking for a 1991 (Never can remember if '90's got them too) diesel truck with 4L80E would be the ticket. Use the column and all that, wouldn't need to change hardly anything, at least as far as I can think of. Not much of an expert on those trucks though, if you've got 12V for the transmission and column, you might be set.

 

[muddermilitia]

Have you looked at a Gear Vendors overdrive unit?

EDIT: nevermind, just looked it up and they are over 2 grand!!

 

[CUCV2]

I would like to find the '91 setup and have been looking for awhile but I realize now why they call that year the Holy Grail. It eludes me still. And trying to find a usable 4L80E vs. one that needs a rebuild is a factor. The one I found is ready to go for a price I can live with. The total cost factor will be around $1400. That seems more affordable than a new truck by far. Not that I would prefer a newer truck anyways. The CUCV was the truck of choice because it is easy to work on and is heavy duty. I am just trying to make the best of both worlds here.

 

[CUCV2]

Have you looked at a Gear Vendors overdrive unit?

Good idea. I hadn't looked at that. I just did though. It says that will run about $2800 plus a new DS.

That reminds me of another idea I read about where someone used a STAK (IIRC) 3 speed TC and one of the gear reductions was .75 to 1. That was pretty pricey as well but it would seem a little more worth it to get rid of the 208 and get OD and a additional 4 to 1 gear reduction as well. More $ than I can spare though.

EDIT: You beat me to the price quote.

 

[BKinzey]

Who makes the "Black Box?" It's an overdrive, small, and is black of course. IIRC it's cheaper than the Gear Vendors unit.

 

[muddermilitia]

Who makes the "Black Box?" It's an overdrive, small, and is black of course. IIRC it's cheaper than the Gear Vendors unit.

Northwest fabworks makes that but it's actually an underdrive so it will have negative effect in this situation. It would be cool if you could flip it around but I think the gear ratio would be too low (numerically too high)

 

[Masiony]

the simple solution is taller gears. if you are running the same RPM with a 4l80 and 4.56 as a 400 and say 3.30 gears (not that they are available, but it illustrates my point) what is the advantage? IMO, Overdrive is a myth and the only benefit i see is the ability to run higher numerically gear sets and therefor have better low end power.

 

[CUCV2]

the simple solution is taller gears. if you are running the same RPM with a 4l80 and 4.56 as a 400 and say 3.30 gears (not that they are available, but it illustrates my point) what is the advantage?

How much would it cost to change gears compared to the tranny? The brakes seem application specific (they're hugemongous). I think the driveshaft yokes are 1410s (correct me if I am wrong). That and a gear change to higher gears just seems wrong to me. I have thought about it but the tranny swap actually seems easier. That is if the 400 and 4L80E are similar in length.

IMO, Overdrive is a myth and the only benefit i see is the ability to run higher numerically gear sets and therefor have better low end power.

I need the low end power.

It would be nice to here from someone who did the swap to get their opinion on whether it was worth it. I just know that driving 50mph ahd getting passed by granny smith is no longer entertaining. That and you can add 20-30% more time to make every trip you take.

Someone else must have done this. Input is greatly appreciated.

 

[fourwheelerjeff]

it seems you are dead set on the 4L80E; personally, i am thinking of finding a couple of diesel 700r4's. 1 for my m1009 and another for my m1008. it this for your m1008 that says DD in your sig? what tires are you currently running? i plan on running 37's on the street in both of mine and maybe 38's offroad.
the thing about changing ratio's is you lose the low end grunt of the low gears.

 

[Smitty]

I was also the guy that wouldn't do over 60 mph on the highway. The 4.56 gears were just not made to do highway speeds behind a TH400. I would have gone with an OD transmission, but they were way out of my price range. I installed 3.73 gears and I'm sorta happy with the result. I can now do the speed limit, but I gave up a little bit in the lower rpm range. The 6.2 is no powerhouse and it needs every little bit it can get.

I'd say going with the OD transmission is really the way to go if you can afford it.

 

[dyeager535]

I was just thinking of finding someone parting out a truck, not buying a complete truck.

OD is no myth. Especially for guys that like to go downhill at controlled speeds with little to no brake input. You can run 4.56's or whatever, get awesome compression braking, yet cruise on the freeway at reasonable RPM's. ESPECIALLY with those diesels, which make me cringe hearing them piss-wrapped at 60MPH!

I've got 3.42's, my dad's got 4.10's. His truck has infinitely better compression braking than I do, if I don't hit the brakes my downhill speed quickly becomes a problem.

Cost vs. benefit for mileage alone, it's pretty much a wash IMO, since putting overdrive in tends to be pricey no matter how you cut it.

 

[CUCV2]

it seems you are dead set on the 4L80E; personally, i am thinking of finding a couple of diesel 700r4's. 1 for my m1009 and another for my m1008. it this for your m1008 that says DD in your sig? what tires are you currently running? i plan on running 37's on the street in both of mine and maybe 38's offroad.
the thing about changing ratio's is you lose the low end grunt of the low gears.

The tires on the M1008 are stock. I do have some 35s that I put on it for summer but the speed change seemed marginal. Which truck the 4L80E is going into, oddly enough, depends on what is involved to put it in. If I need new driveshafts, it is going in the M1028 since I want to make it a SWB truck anyway. Then I would just sell the M1008. The M1028 could be a good all around truck. The M1008 has the reliability factor going for it since it doesn't get wheeled but as you can tell from my sig, I can wheel something else besides the M1028.

 

[CUCV2]

I was also the guy that wouldn't do over 60 mph on the highway. The 4.56 gears were just not made to do highway speeds behind a TH400. I would have gone with an OD transmission, but they were way out of my price range. I installed 3.73 gears and I'm sorta happy with the result. I can now do the speed limit, but I gave up a little bit in the lower rpm range. The 6.2 is no powerhouse and it needs every little bit it can get.

I'd say going with the OD transmission is really the way to go if you can afford it.

Thanks for the insight. I was actually looking at some 1 ton axles with the 3.73s and wondered how it would work out. They were about the same price as the 4L80E. I know I could have recouped the cost by selling 4.56s but knowing me, I would have just saved them for another project that I don't need right now. So the 4L80E is actually cheaper.

 

[CUCV2]

I was just thinking of finding someone parting out a truck, not buying a complete truck.

OD is no myth. Especially for guys that like to go downhill at controlled speeds with little to no brake input. You can run 4.56's or whatever, get awesome compression braking, yet cruise on the freeway at reasonable RPM's. ESPECIALLY with those diesels, which make me cringe hearing them piss-wrapped at 60MPH!

I've got 3.42's, my dad's got 4.10's. His truck has infinitely better compression braking than I do, if I don't hit the brakes my downhill speed quickly becomes a problem.

Cost vs. benefit for mileage alone, it's pretty much a wash IMO, since putting overdrive in tends to be pricey no matter how you cut it.

Wow, more good insight . Never even thought about compression braking.

I would settle for a "wash" with the cost vs. benefit if it made the truck that much more enjoyable to drive. Even at 50-55 mph the 6.2 is loud enough. When you drop down to 45mph it sounds like it is at it's happy medium. I am hoping that OD will put the happy medium at 65mph.

 

[sandracer799]

1- Mods must be made for the computer controls
2- Shifter may have to be modified
3- TC will need to be converted to the passenger side

I just recently did the 4L80E swap in my 87 blazer, by far the best mod I have done.

I just used the transfer case that was in my truck (208) and it bolted right up to the 4L80 with no problems. As for the shifter I just had to lengthen the shift linkage and transfer case linkages about 3 inches no biggie.

Also Driveshafts. Front drive shaft has to be lengthen and the rear shortened due to the length.

As for the controlling aspect of things I went with the TCI stand alone unit. This kit is awesome. It allows you to do whatever you want with the transmission. How hard you want it to shift, when you want it to shift, when and how hard you want it to shift at a certain throttle %. It is awesome.

I say go for the 4L80 you wont regret it.