What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

CUCV Needs OD

dyeager535 said:
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.
Click to expand...

Diesels have practically no compression braking so I would say that is not a factor.


OD isn't a myth either, adding another gear to the trans has a lot of advantages. It lets you have a deep first gear (for easy starts) and a wide top gear (for highway cruising).
 
I will also say that OD is no myth. If you just change axle gears it will be a compromise one way or the other...put something like 3.08 and it will cruise at 65 mph better but you lose the low-end power, stay with 4.56 and have good low-end but crappy highway performance. 3.73's are a compromise...lose some low-end and still marginal on the highway with stock tires (31"). An OD trans gives you the best of both worlds.

I've owned my 6.2/700r4 K5 since '94, and back when it was a DD it had 3.73 w/ 32" tires, and then 4.10 w/ 33" tires and it was really happy on the highway at 65-70 mph. Final cruising ratio in OD w/ 4.10s was 2.87 (4.10 x .70)...which is why I said 3.73 w/ 31's would still be marginal on the highway.

My first thought was 700r4, but you mentioned towing which would be the only downside. However I have seen a properly built 700r4 hold up pretty good to occassional towing.
 
sandracer799 said:
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.
Click to expand...

What year 4L80E is that and what did it come out of? Did you find a reasonable price on the TCI controller? I am hoping the TH400 that is in the CUCV is closer in length to the 4L80E.

38377k5 said:
Diesels have practically no compression braking so I would say that is not a factor.


OD isn't a myth either, adding another gear to the trans has a lot of advantages. It lets you have a deep first gear (for easy starts) and a wide top gear (for highway cruising).
Click to expand...

I am curious as to what the gearing is on the 4L80E and how it compares to the TH 400. I thought I read somewhere it is similar, just with OD. It would be great if it had a deep 1st like the 700R4. I think you were referring more to axle gears but one thought led to another.

6.2Blazer said:
I will also say that OD is no myth. If you just change axle gears it will be a compromise one way or the other...put something like 3.08 and it will cruise at 65 mph better but you lose the low-end power, stay with 4.56 and have good low-end but crappy highway performance. 3.73's are a compromise...lose some low-end and still marginal on the highway with stock tires (31"). An OD trans gives you the best of both worlds.

I've owned my 6.2/700r4 K5 since '94, and back when it was a DD it had 3.73 w/ 32" tires, and then 4.10 w/ 33" tires and it was really happy on the highway at 65-70 mph. Final cruising ratio in OD w/ 4.10s was 2.87 (4.10 x .70)...which is why I said 3.73 w/ 31's would still be marginal on the highway.

My first thought was 700r4, but you mentioned towing which would be the only downside. However I have seen a properly built 700r4 hold up pretty good to occassional towing.
Click to expand...

Makes me wonder if OD will be enough with the 4.56s. Probably close enough to work with. Like putting the 35s back on determining the ideal tire size.


Getting some good info here. Mucho thanks so far.
 
CUCV2 said:
What year 4L80E is that and what did it come out of? Did you find a reasonable price on the TCI controller? I am hoping the TH400 that is in the CUCV is closer in length to the 4L80E.
Click to expand...

My 4L80 came out of a 95 K3500 with the 6.5. The controller I got from summit for $900 pricey I know but well worth it.

I had a built 400 in my Blazer that I swapped for the 4L80E, and the 4L80 is in fact 3 inches longer.

I forgot to add in my first post because of the difference in length you have to relocate the crossmember back too.

Hope this helps
 
sandracer799 said:
My 4L80 came out of a 95 K3500 with the 6.5. The controller I got from summit for $900 pricey I know but well worth it.

I had a built 400 in my Blazer that I swapped for the 4L80E, and the 4L80 is in fact 3 inches longer.

I forgot to add in my first post because of the difference in length you have to relocate the crossmember back too.

Hope this helps
Click to expand...

Yeah, that is very helpful. Raising more Qs though. What is the difference if the tranny came out of a diesel or not? I looked up torque converters and it looked the same for the diesel or gas. Is the computer different or is there something in the tranny itself that is different? Thanks.
 
CUCV2 said:
Yeah, that is very helpful. Raising more Qs though. What is the difference if the tranny came out of a diesel or not? I looked up torque converters and it looked the same for the diesel or gas. Is the computer different or is there something in the tranny itself that is different? Thanks.
Click to expand...

There is no difference that I am aware of. As far as the Torque converter goes I used the one that came with the transmission. The diesel converters have 6 bolts where the gassers normally have 3, however I had a multi-pattern fly wheel so I was able to get 3 of the holes to line up and that is what I used.

I have the 383HT in my Blazer. I thought the diesel converter was going to be way to low of a stall but I figured I would give it a try before shelling out another 500 bucks on a new one. It works awesome. My motor makes gobs of torque down low and it put it right in its power band so I kept the converter that came off the 6.5.
 
sandracer799 said:
There is no difference that I am aware of. As far as the Torque converter goes I used the one that came with the transmission. The diesel converters have 6 bolts where the gassers normally have 3, however I had a multi-pattern fly wheel so I was able to get 3 of the holes to line up and that is what I used.

I have the 383HT in my Blazer. I thought the diesel converter was going to be way to low of a stall but I figured I would give it a try before shelling out another 500 bucks on a new one. It works awesome. My motor makes gobs of torque down low and it put it right in its power band so I kept the converter that came off the 6.5.
Click to expand...

Any issues with the starter or did that bolt right up as well?
 
CUCV2 said:
Makes me wonder if OD will be enough with the 4.56s. Probably close enough to work with. Like putting the 35s back on determining the ideal tire size.
Click to expand...

I think it will be substantially better. I have a 4L80 in my DD and there is somewhere around 800-900 rpm drop between 3rd and OD. It would be like going from the 4.56's down to 3.42 gears, I think it would be great for 35's based on my experience.

The 4L80 has the exact same ratios as the TH400, with the addition of the 0.75:1 overdrive.

Regarding the comment about diesel's having no compression braking, I'm not too sure about that argument. My diesel K5 with an auto and a "marginal on paper" 34:1 crawl ratio let's me crawl down a fairly steep fill without touching the brakes. Going down the same hill in my gas DD with a 28:1 ratio I had to use the brakes quite a bit to control my speed. I know it's slightly less of a ratio, but using the rationale that diesels have no compression braking it should be the other way around regarding how much brakes are required.
 
6.2Blazer said:
Regarding the comment about diesel's having no compression braking, I'm not too sure about that argument. My diesel K5 with an auto and a "marginal on paper" 34:1 crawl ratio let's me crawl down a fairly steep fill without touching the brakes. Going down the same hill in my gas DD with a 28:1 ratio I had to use the brakes quite a bit to control my speed. I know it's slightly less of a ratio, but using the rationale that diesels have no compression braking it should be the other way around regarding how much brakes are required.
Click to expand...

Diesels don't have butterflies to block of the intake like gas motors do. That means they are pumping full cylinders of air all the time. "Choking" the motor with the butterflies is where nearly all of the compression braking comes from. Diesels don't choke the motor when you're off the throttle which is why big rigs have jake brakes.

My CTD tow rig has hardly any compression braking. Downshifting helps a little bit (probably mostly from internal friction in the motor and spinning the fan faster).
 
Ok then! :)

If compression braking isn't a big feature, then the better acceleration/towing capability of being able to run something like 4.56's has to be a plus, right?
 
pennsylvaniaboy said:
well od is great. and a bigger tire will help alot. and secondly im not getting why you need transfer case mods? also for your different tranny ratios here is a good sitehttp://www.4lo.com/calc/gearratio.htm and there are other calculators out there too that will tell you your drop in rpm
Click to expand...

Thanks for the calc. The TC off the 4L80e was on the drivers side and I would like to use the passenger side 208 on the CUCV. I was under the impression that the bolt pattern would be off to just bolt the 208 on. I am no TC guru so please correct me if I am wrong.
 
Oh yeah, and on compression braking, isn't it the high compression ratio of the motor that actually slows you down. If there is no fuel going in, wouldn't that just leave the compression slowing you down. I know I can go down a steep grade and let off the skinny pedal and slow down easily enough. But then again, the truck needs OD so maybe it is just the low gears doing the work.
 
There was a guy who did this exact install on his 1008/1028 a while ago over on www.SteelSoldiers.com . Are you a member there?


Frankly...for all the cost and work he went through I'd put a NV4500 in and row my own gears. However since you have a 4L80E already you're ahead in that regards.


Frankly I'd get a built to the hilt 700R4 setup for towing and high power setups with all the latest doo dads and go from there. Years ago my dad toasted the one in our '92 Blazer K1500 and had a local trans shop beef the heck out of it. That truck towed a 28' travel trailer all over the midwest for another two years before he sold it to me. Trans was fine.

I put 38's on and cut to fit to overcome the gears. Basically it's now like having 31" tall tires and 3.73 gears. Still gets up and goes nicely but can actually do 65mph. OD would be nice but I'm not terribly worried about it now. Doesn't sound like the engine is coming through the firewall anymore.
 
AJMBLAZER said:
There was a guy who did this exact install on his 1008/1028 a while ago over on www.SteelSoldiers.com . Are you a member there?

No, but if you have a link that would be great.

Frankly...for all the cost and work he went through I'd put a NV4500 in and row my own gears. However since you have a 4L80E already you're ahead in that regards.

I saw where they did that in 4W&OR. It looked like a great set-up. More work than I wanted though. Finding an NV4500 in good shape is tough. Plus you need the pedals, the clutch, adapter, and what ever else (starter mod IIRC). I remember reading the article and thinking that it was more work than I wanted. All I really want is OD and the 4L80E just seems like the ticket. I'd like to talk to someone who has used a manual valve body and get some input on that as well. Sounds like a mix of driving a standard and an auto which is fine with me. This is one of the reasons the floor shifter option came up.

Frankly I'd get a built to the hilt 700R4 setup for towing and high power setups with all the latest doo dads and go from there. Years ago my dad toasted the one in our '92 Blazer K1500 and had a local trans shop beef the heck out of it. That truck towed a 28' travel trailer all over the midwest for another two years before he sold it to me. Trans was fine.

Seems like that would cost the same or more as the 4L80E and I need a 32 spline rear output shaft for the tcase.

I put 38's on and cut to fit to overcome the gears. Basically it's now like having 31" tall tires and 3.73 gears. Still gets up and goes nicely but can actually do 65mph. OD would be nice but I'm not terribly worried about it now. Doesn't sound like the engine is coming through the firewall anymore.

How's that flex :wink1: ? 38s probably would negate any mileage gains and towing power. Not that mileage is a high priority issue but if the 4L80E will pay for itself with mileage, so be it. I did see some pics of your truck and thought it was pretty cool to stuff 38s with no lift. That is one of the things I like about these trucks. Pretty easy to get up to a 39.5" tire. Yours is the first one I've seen with that size tire and no lift. Props:bow:
Click to expand...

Thanks for all the input so far.
 
Hahaha, it flexes like a 1 ton...so not a lot. The Tracker and Big Ugly talk **** to each other about how little they flex.
364830_209_full.jpg


http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=11045&highlight=4l80
Turns out there's more:
http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=10408&highlight=4l80
http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=12148&highlight=4l80
 
pennsylvaniaboy said:
well od is great. and a bigger tire will help alot. and secondly im not getting why you need transfer case mods? also for your different tranny ratios here is a good sitehttp://www.4lo.com/calc/gearratio.htm and there are other calculators out there too that will tell you your drop in rpm
Click to expand...

After playing around with the calc, here are some interesting numbers.

My ideal cruising speed was about 50mph before the rpms were getting too high. That same rpm with OD will allow me to go about 67mph. If I go with a bigger tire that would lower the rpms a little more even. I'm beginning to wonder what kind of mileage gains will come of this. I am guessing 20miles/gallon. That would be incredible for a 84 Chevy 1 ton. The truck gets somewhere in the mid teens now.
 
A lot of the K5/Suburban/ 3/4 ton guys with the 6.2's and 700R4's report near 20mpg easily around town when properly geared for their tires and keeping the engine happy.
 
AJMBLAZER said:
A lot of the K5/Suburban/ 3/4 ton guys with the 6.2's and 700R4's report near 20mpg easily around town when properly geared for their tires and keeping the engine happy.
Click to expand...

Sweet pic of the 38" 1 ton full stuff :D. That is where it is at.

Sounds like 20mpg is a decent guesstimate then.

I am going to be busy for a while reading those links. I just started and so far it is confirming some of the things we have covered here. Thanks for the links. Keep stuffing those 38s.;)

EDIT: Ok, I read them and it made me want to use the manual valve body more since the computer controls are some of the major hiccups and high cost items that can occur. My $1400 seems like a bargain compared to what some of those guys shelled out. I only read about one guy who actually finished it up and got to run it. He sounded pretty happy with the reduced rpms and noise level. There was also a blip about the tcase bolt pattern being different for the d-side case as opposed to the p-side case. But that turned out to be an easy fix thanks to Kert at DIY4X. As I stated initially, he is taking a 208/241 clocking ring and found an alignment that clocks the tcase up some and adapts the adapter (that sounds funky). THANKS KERT.
http://www.diy4x.com/drivetrain.htm
 
Last edited:
You must log in or register to reply here.

Latest Posts

Top Bottom