Battery in and new terminals installed. No more over charging or melting wires. Truck fires up on its own now and actually idles. Now to track down a massive oil leak and finish up some wiring. Oh, and I finally have my driveway back.
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.
'86 Jimmy 4in Lift, 40’s, tons, 8.1 Swap- 700r4 said PNNNNN
- Thread starter GWeakland620
- Start date
This is not a dedicated trail rig, but does trailer to the destination usually. I am currently in the planning phase of doing a 52/56" spring swap, and getting back to being more road worthy.
I know I have squirrelled a lot lately on this build, but I am trying to narrow down what we want from this truck. I even thought of selling it this last week or two, but I just can't bring myself to do it. As our family grows, our desires to do different activities changes. We like the idea of exploration more than hardcore trails and rock crawling. So instead of starting over with a build, I am going to use what parts I have now and start to refocus on this build. The new direction is something more family oriented with comfort.
I'm to the point that I am sick and tired of the small block and horrible efi system. I want to start over.
So that being said, I am going to swap in the 8.1 BBC. We just got a truck in here at work that they are letting me pull off all of the accessories and wiring harness to dress my 8.1L. It's cheap enough that I should be able to have this 8.1 dressed and ready to start
the swap for around $500. I know there will be a lot more purchases once the actual swap starts, but this gets me a modern efi engine with plenty of power and reliability in there to make me very happy. I'm sure I'll be blowing up @Kay86K5 's phone a ton, but I know the 8.1 resource thread will be my home while I get after it.
So the plan going forward is to finish the 4x4 swap in the crew cab. Then shoe horn this truck into the garage for the winter and take my time. I don't want to end up with problems like I did from rushing the first time.
I'm to the point that I am sick and tired of the small block and horrible efi system. I want to start over.
So that being said, I am going to swap in the 8.1 BBC. We just got a truck in here at work that they are letting me pull off all of the accessories and wiring harness to dress my 8.1L. It's cheap enough that I should be able to have this 8.1 dressed and ready to start
the swap for around $500. I know there will be a lot more purchases once the actual swap starts, but this gets me a modern efi engine with plenty of power and reliability in there to make me very happy. I'm sure I'll be blowing up @Kay86K5 's phone a ton, but I know the 8.1 resource thread will be my home while I get after it.
So the plan going forward is to finish the 4x4 swap in the crew cab. Then shoe horn this truck into the garage for the winter and take my time. I don't want to end up with problems like I did from rushing the first time.
Give me a call/text anytime. I tried to document in my crew cab thread as best I could for the swap too. So hopefully that can be a good resource for the 8.1 swap too
Yep! I planned on reading through that again too. Thanks dude!
That sounds like a good plan. I don't have time to wheel at all lately but my wife always tells me she wants to go do some tent camping trips with the blazer. That's what I intended mine for, general off-road use and exploring and having fun. I have gone from being single to a 6 person family since I have owned it though so I wouldn't mind turning mine into a daily driver and getting a suburban to build for the duties the blazer does so we can have some more room. Heck by the time I get around to doing anything the wife might be ready for something different for her DD and I can do a build on the Yukon XL Denali that she drives.
One question I do have is, what direction do I go for a trans?
I have that good/strong 700r4 in there now, but I'm not so sure about that 8.1 in front of it.
I have a TH400 that most likely needs a rebuilt and a 208 adapter so I could use my SYE 208 t-case.
I have that good/strong 700r4 in there now, but I'm not so sure about that 8.1 in front of it.
I have a TH400 that most likely needs a rebuilt and a 208 adapter so I could use my SYE 208 t-case.
Yeah goals and family have changed in the 2 years the K5 has been down. I don't want to sell it, cause some day I'll be back to the original activities, but the family has no desire to hop in a crawler that isn't reliable and makes me angry lol.
If you have a TH400, I would use that. Not saying a 700r4 couldn't hang for a while, but there are other aspects you have to worry about. Mainly the TV cable. And that also will depend if you want to run the DBW on the 8.1, or convert the 8.1 to drive by cable. Obviously keeping the 700r4 you would pretty much be forced to go drive by cable to have some sort of mechanical arm to use to get a TV working properly, but then you have to deal with possibly a aftermarket/custom TV cable to reach to the front of the motor where the 8.1 throttle body is (as opposed to in the middle and on top of the motor like old SBC's like all 700r4's were bolted to). It can be done as many people have run 700r4's being LS's (which have the same location of the throttle body) but it's just things to consider.
That's why to me, if you have a TH400 that you can bolt your current tcase to, even if it needs a rebuild, it would be worth it to run the TH400. Just sell your good working 700r4 to help aid some costs of the motor/trans swap
Yeah I like that route.
Yeah I vote TH400 since I'm guessing overdrive on a big block rig like that won't help much anyway. The low first gear on the 700 would be nice but not worth it.
I know it's easier said than done, but if it were me, I'd try to find a 4l80e because the 8.1L ECM can control it. You said the 400 likely needs a rebuild anyway. You could try to sell the 700r4. Especially right now when you can drive it and demonstrate if functions well. I paid $800 for a 95 truck with a 4l80e that had recently been rebuilt. Pulled the trans and sold the rest of the truck for $400. I know that's not an everyday deal, but they're out there.
Well now that you say this, I have a 2wd 4L80 coming out of my crew cab. I could pick up that adapter from Tnsejed and hook my 208 up to that!!!
Yeah, Todd (@Tnsejed) and I talked a lot about the 4l80e stuff before I got mine. He knows his stuff. There's an advantage to the 2wd I can't remember now. Oh maybe it's the output speed sensor and not having to retrofit it into the transfer case. One thing I like about the 4l80e is the input and output speed sensors so it can detect torque converter slip.
You should verify the 8.1L can control the 4l80e; I'm just assuming it can. IIRC didn't the 8.1L come with Allinson tranmissions?
The 8.1's came with the Allison in trucks. The Suburban and Avalanches came paired to the 4L80E's.
I'm slammed today or I'd dig for the actual 8.1l ecm numbers. But I did find a howell 8.1l 4l80e harness. So I assume the ECM for the vortec 8100 either has 4l80e provision possible, or is segment swappable.
Finding the ecm number then researching from there will tell you which direction to go. For me I'm a 2wd tranny fan. VSS and length is sweet. And hell, I have an LS3 running on a 0411 controlling my 4l80e segment swapped with two vehicles. So what your trying to do should be a snap.
I'll be honest, I didn't understand most of that.
But what I got was "What your trying to do should be a snap.", and I like the sound of that.
Haha. Sorry. Segment swap means using two different vehicle programs inside and ECM, more or less. So you will use one vehicle program for the engine controls and one for the transmission controls. You combine them using tuning software. Its pretty straightforward and you, or your tuner could do it.
That's worst case scenario. That would be if the 8.1l never came from the factory with a 4l80e. If it did you just find that ecm part number and use that ecm. Most likely having to repin out the harness. That's pretty easy as well.
Also to note, I'm finding threads on HPtuners of guys tuning the 8.1l/4l80e combo. More searching shows its a pretty popular combo and their seems to be some possible aftermarket packs with it. Check for G30 ecm's as well.
I'll start checking our inventory for some 8.1/4L80 combo vehicles.
I was going to mention vans. They had Duramax engines with 4L80 trans in them so I'm sure the 8.1L also got it. Maybe even workhorse step vans like FedEx ones too.
