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4l80e crossmember

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74kay5

1/2 ton status
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I have an 85 K5 and was wondering if anyone has done a 4L80E swap on an older truck like mine. I know the crossmember has to be modified or moved back but the mounting points for the adapter are also different. If some of the diesel suburbans had the 4L80E can I just go to the junkyard and get a crossmember from one of those? It would be the right width for my frame and have the right mounting locations I'm guessing. Anyone know for sure though?
 
What are the differences in the mounting point? I'm certain what I'm using (NP208 or 241 "double hump" crossmember, '81 frame) has the same trans mount as what was originally on the 4L80E/205 combo that donated my 205. Short adapter, one piece transmission mount.
 
What kind of truck do you have, is it a K5? And could I use a TH400 mount as well?
 
It's a K5.

I don't *think* the TH400 mount is the same. It might be, but the only Th400 I ever owned was in a car, and it had one mount to crossmember stud. I'm pretty sure the truck uses two nuts for two studs that stick out of it. They are metric as well.
 
74kay5 said:
And could I use a TH400 mount as well?
Click to expand...


Are you asking if you can use a 2WD TH400 Tranny mount, or a 4WD TH400 Tranny mount (Actually the 4WD mount is a T-case mount, but MANY people and even parts counter staff still refer to it as a 4WD tranny mount)?

I've been researching this as I am planning to run a 4L80/NP205 as soon as I figure out my motor issues :mad:


The question is what t-case are you planning to run? What front axle are you going to run (which will dictate passenger's side drop or driver's side drop). I'm assuming you are using the stock axle so it will be a passenger's side drop, but thought I'ld ask to make sure.

The 4L80 had a NP205 mated to it for a couple years (or possibly only one...1991) and the adapter is almost impossible to find. It used a round pattern 205 with the late style crossmember (double hump) and short adapter. The NP205 combo is best suited for passenger's side drops, but a Ford unit could be custom matched for a driver's side drop. The 4L80 also was mated to a 241 (number?????) and can be found with all the necessary adapters, crossmembers, shifters etc. for a fairly reasonable price. I don't know what the availability of the 241 is for passenger's side drop, but I know they are available for driver's side drop.

You can run a TH400/NP205 adapter to mate a 4L80 and NP205 but you have to have the correct adapter and t-case (figure 8 vs. 6 bolt round patterns) and correct crossmember. You need to slightly machine the adapter for the 4L80 seal. You may also run a spacer to run a 2WD 4L80 which I believe one member here already did.

I'm still a little foggy and trying to nail down one point and maybe somebody can shed some light.

This is one combo that I'm trying to go with to use the short 6 bolt circular adapter (broken too many tall TH350/NP205 ones), but not sure on a one thing.

I plan to use a stock output 4WD 4L80, 6 bolt circular short TH400/NP205 adapter machined for 4L80 oring seal, round pattern NP205, double hump crossmember, Modified shifter.

The only question is what input shaft does this combo use? There is a short 32 spline female and a long 32 spline female input shaft available for the NP205. Is the long one too long and/or the short one too short for this combo (trying to run without an extra spacer/adapter), or is one just right??????

Hope this helps you a little and didn't confuse anyone, and hopefully someone can shed light on my question.
 
I'm using the same 205/input w/ a 32 spline 465 as was used with the 4L80E donor truck.

From the pictures I've compared with mine, it's the "long" 205 32 spline input.
 
I'm using an NP 241C. Got the 4l80e to 241c adapter from a 91 suburban. But it's the mount that goes onto this adapter (4WD mount) that I need. Plus it has to sit up higher because the stock one sits pretty low.
 
I hope these help out, somehow:

1569trans_rear.JPG


1569trans_mount.jpg


1569mount_nuts.JPG


1569adapter.JPG


Sorry they aren't any better, I just held the camera under the truck and hoped they turned out.

Forgot I went with the goofy shaped crossmember, tried both, liked this one better. They put the trans mount at the same "height" regardless.
 
i am the one with the 2x4 fixed yoke to 4x4 fig 8 style long female input 205 with spacer. 1 1/4" thick spacer and no cutting to tranny shaft. 4l80-e seal lip on 1 side and 400 style seal lip on otherside. easy to make. also just need to change the oil plug at the 3 oclock position out to a 4x4 soild plug as ne need to have tranny oil come to the fixed yoke bearing anymore and if not done will cause severe losse of oil pressure on that circit. easy swap for 5.00 bucks at dealer for plug.

biggest benifet is no clearence problems with cv shaft head at tranny pan.

205 spacer.jpg
 
i THINK the cross member on the 4l80e is a hydroformed bit. i cant remember though. it would be wider than your frame rails, but thats a good thing. you can cut it down as needed, and add some angle iron to bolt it in where needed.
Grant
 
Frame width isn't different on the one tons, and the crossmembers are the same.

The frame height is different, the crossmember is mounted inside the framerail (above the lower "lip") to make up the height difference and keep the entire drivetrains relationship to the body the same as any 1/2 or 3/4 ton truck.
 
I Have One Of Those Crossmembers Sitting In My Garage Right Now That I Was Going To Use For A Different Tcase But It Didnt Fit So There It Sits.
 
Those pictures were very useful, I ended up buying a double hump crossmember like yours at the junkyard. Is your transmission the same length as a 4l80E though? Could you take pictures of the actual studs where the hardware is mounted to the frame. That way I can compare the location that my holes were drilled to yours. Thanks again for all the responses. I'll take pictures as well when it stops raining.
 
What you need to do is bolt the trans up to the motor, bolt the adapter on, bolt the crossmember to the adapter with the mount, line everything up on center, push the assembly against the frame with a floor jack or similar, and drill the bolt holes wherever necessary for the crossmember. That is exactly what I had to do.

The *overall combination length* I believe is the same on the later trans/transfer case combo's, (made up in the adapter) because it saved GM from having different length driveshafts where possible.
 
dyeager535 said:
What you need to do is bolt the trans up to the motor, bolt the adapter on, bolt the crossmember to the adapter with the mount, line everything up on center, push the assembly against the frame with a floor jack or similar, and drill the bolt holes wherever necessary for the crossmember. That is exactly what I had to do.

The *overall combination length* I believe is the same on the later trans/transfer case combo's, (made up in the adapter) because it saved GM from having different length driveshafts where possible.
Click to expand...

This is the way I did mine when I did the 700R4/NP205 combo. The biggest thing to be concerned with is that the framerails tend to "move in" when the crossmember is not bolted to them. I put the mounted assembly against the frame, marked the holes with a grease pen (chalk could be used as well). Dropped the crossmember down and used the existing holes in the frame to get the centerline of the bolt holes. I also made sure the crossmember was perpendicular to the frame as my marks were slightly forward on one side and slightly aft on the other. I split the difference (using the existing holes to make measurements from) and this gave me holes that were centered on the frame (or at least in line with the originals) and were equal distance back on the frame (which keeps the crossmember perpendicular). This made sure that the frame was kept in its original alignment and that the motor/trans assembley was straight in the chassis....

Hope this helps.
 
4L80e electronic controllers?

What are you guys doing for the electronic controller? I know an aftermarket box is available ($$$), but are there junk yard options which actually work, and if so what are they and what is required for install?

Also, has anyone tried to hook up a 203/205 doubler to a 4L80e?
Thanks in advance
 
Yes, good point. It's pretty hard to determine the actual centerline, using the existing bolt holes to calculate is a good idea.

About the controller...if you do a search on this board, you'll find a post where I and others did some research on what existed out there (stock) that might actually work. A stock ECM sure sounds cheaper than the multi-hundreds of dollars the aftermarket controllers cost.
 
For a stand alone controller for the 4l80E if you can find one in a junkyard has to come from a mechanically injected Diesel they were the only ones with a stand alone tranny controller the gasoline engines had the controller built into the ECM.

Ira
 
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