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Gen 3 swap question

firemedicsafd

firemedicsafd

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I just finished my SYE kit on my 241 and wanted to know something. How much does a Gen III swap move the motor and trans combo? Is it small enough to go ahead an purchase the driveshafts and use the new 241 in the old set-up behind the 700R4 and 305? Im asking because i want to use it now but if i have to buy all new shafts after i do a 6.0/4L80E swap then it would not be cost effective to buy them twice. The swap is a while away as i do not have a donor motor/trans yet. Thank s for all the input!
 
700r4 is shorter than the 4l80-e trans first off . so there is a length difference .

and most ls swap mounts now can keep the engine bell housing in the same location . but some do get moved a little bit .

so knowing these 2 points you will need modifyed shaft length for front and rear when you do the 6.0/4l80-e swap .

good point is shorten a shaft is cheeper than length added as thats new tube .
 
And if you are going to use any trans with an 80E on the end, the spline count for the output shaft is 32, where as your 700 has a 27 spline...
 
does the NP 208 or 241 have 27 or 32 spline? i remember something during the 700R4 rebuild about converting it to the 32 spline but I'm not sure which end. Guess can count the 241 since its on the shelf right now
 
241's came in both versions, so either way, you can (and should) use the 241. Might just need a little more surgery...
 
firemedicsafd said:
oh i know that. SYE kit just got installed last week. Now ill need to know if i have to open it up again to replace the input shaft for the 4L80E
Click to expand...

There’s nothing to doing the input shaft swap. You’ve already been in it and are familiar with the internals so it should be easy whenever the time comes.
 
Going back to the original question. Drivetrain location with the swap. Depending on the engine swap mount brackets you use some put the engine forward or rearward of a stock SBC. Some stick right at the stock SBC location, others are adjustable. By Location I'm talking about the transmission bellhousing flange. I use Dirty Dingo slider mounts and put the 5.3 in the stock SBC location. Be aware that even in the stock SBC location, the 5.3 is really close to the firewall on the driver's side. Mine was close enough the exhaust manifold was just barely touching when the engine under load. Had to tweak the pinch weld seam so it wouldn't touch anymore.

On a Blazer I don't think you want to push it back anymore than stock even if you could as it would compound your driveshaft length and angle issues.
 
So, i have a 27 spline input shaft (DAMMIT). Where would i go to get the 32 spline so the 4L80E transmission will bolt up?

IMG_4220.JPG
 
Oh yeah, those snap rings suck. Best to get lock ring pliers vs snap ring pliers. I got my shaft from ORD but they can be found elsewhere.
 
dont forget the adaptor required to fit the 4l80 trans . the th400 is real close but the seal lip seat is a tad off on dia from 400 to 4l80 .
 
Found mine in the boneyard. My original 241 was messed up so I had to find another. Funny thing was I needed a 27 spline and I ended up with a 32 spline. Didn't count the splines and it got installed. For the life of us we couldn't figure out why it wouldn't hold in park. Finally pulled it and counted the splines. So I had to swap inputs to get what I needed. I don't plan on selling it as I may end up with a nv4500 and need the 32 spline.
 
sweetk30 said:
dont forget the adaptor required to fit the 4l80 trans . the th400 is real close but the seal lip seat is a tad off on dia from 400 to 4l80 .
Click to expand...

It's the index, the male part on the adapter that's machined the same size as the transmission adapter. That's the piece that makes sure the shafts/bearing run concentric, they are a good bit different between a TH400 and 4L80E. Same bolt pattern, easy to screw up.
 
ya there is a adaptor for almost any combo . there is no real direct bolt tranny/tcase that I know of much .
 
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