6l80e to np205 brace

[843angler]

Hello everyone,

First post here but certainly won’t be the last as I’m starting a new project. I have a 76 frame that currently has an np205 installed. I am dropping in a 6l80e with a 6.2 LS. Already have the Advanced Adapter kit but what are my options for this crossmember/brace. I’ll attach a photo of how it currently sits after I pulled the big block out with a turbo 350 trans. Thanks!

 

[CalSgt]

I've never done the 6L80 swap but have done 4 speed SM 465 to 5 speed NV1500 manual to 700R4/4L60 swaps...

From my understanding 6L80 & 700R4/4L60 are approximately the same length, since these chassis have had 700's in them it should be a straightforward process.

Drop the crossmember and 205, remove driveshafts
Mount new engine & trans, support trans with a jack or stand of some sort
Mount 205 (and adapter) to trans
Lift the crossmember up to the 205, drill holes for new position in the frame, and bolt it in
Check output shaft Vs. pinion angle & adjust for proper driveline u-joint phasing
Get rear driveline cut to size and re-balanced
Have a new shaft built for the front (or perhaps a front shaft from a 700R4 truck may be a direct fit)

Depending on what motor mounts you get for the LS swap some of them have a few inches of adjustability built in, you may need to factor that in before determining your final crossmember location. I'd gamble to say if you are going to run electric fans you might be able to get away with sliding the engine forward a few inches if absolutely needed, otherwise I would push it as close to the firewall as possible.

I'm not sure if any of the factory transfer case support braces (from TC to bellhousing) will fit that combination, you may need to fab something to do that.

Here's an example of a 4L60/208 on a 4 Speed/205 crossmember (looks a lot like yours), I had to build an adapter to raise the transmission mount about 2 1/4". This adapted the cross member bolt holes to the new pattern, the engine to sit right (level) and to get the tailshaft to sit at the right angle compared to the pinion.

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[SquareRoot]

I've never done the 6L80 swap but have done 4 speed SM 465 to 5 speed NV1500 manual to 700R4/4L60 swaps...

From my understanding 6L80 & 700R4/4L60 are approximately the same length, since these chassis have had 700's in them it should be a straightforward process.

Drop the crossmember and 205, remove driveshafts
Mount new engine & trans, support trans with a jack or stand of some sort
Mount 205 (and adapter) to trans
Lift the crossmember up to the 205, drill holes for new position in the frame, and bolt it in
Check output shaft Vs. pinion angle & adjust for proper driveline u-joint phasing
Get rear driveline cut to size and re-balanced
Have a new shaft built for the front (or perhaps a front shaft from a 700R4 truck may be a direct fit)

Depending on what motor mounts you get for the LS swap some of them have a few inches of adjustability built in, you may need to factor that in before determining your final crossmember location. I'd gamble to say if you are going to run electric fans you might be able to get away with sliding the engine forward a few inches if absolutely needed, otherwise I would push it as close to the firewall as possible.

I'm not sure if any of the factory transfer case support braces (from TC to bellhousing) will fit that combination, you may need to fab something to do that.

Here's an example of a 4L60/208 on a 4 Speed/205 crossmember (looks a lot like yours), I had to build an adapter to raise the transmission mount about 2 1/4". This adapted the cross member bolt holes to the new pattern, the engine to sit right (level) and to get the tailshaft to sit at the right angle compared to the pinion.

You must be registered for see images attach

Pretty much says it all right there.^^^^^^^

 

[843angler]

I've never done the 6L80 swap but have done 4 speed SM 465 to 5 speed NV1500 manual to 700R4/4L60 swaps...

From my understanding 6L80 & 700R4/4L60 are approximately the same length, since these chassis have had 700's in them it should be a straightforward process.

Drop the crossmember and 205, remove driveshafts
Mount new engine & trans, support trans with a jack or stand of some sort
Mount 205 (and adapter) to trans
Lift the crossmember up to the 205, drill holes for new position in the frame, and bolt it in
Check output shaft Vs. pinion angle & adjust for proper driveline u-joint phasing
Get rear driveline cut to size and re-balanced
Have a new shaft built for the front (or perhaps a front shaft from a 700R4 truck may be a direct fit)

Depending on what motor mounts you get for the LS swap some of them have a few inches of adjustability built in, you may need to factor that in before determining your final crossmember location. I'd gamble to say if you are going to run electric fans you might be able to get away with sliding the engine forward a few inches if absolutely needed, otherwise I would push it as close to the firewall as possible.

I'm not sure if any of the factory transfer case support braces (from TC to bellhousing) will fit that combination, you may need to fab something to do that.

Here's an example of a 4L60/208 on a 4 Speed/205 crossmember (looks a lot like yours), I had to build an adapter to raise the transmission mount about 2 1/4". This adapted the cross member bolt holes to the new pattern, the engine to sit right (level) and to get the tailshaft to sit at the right angle compared to the pinion.

You must be registered for see images attach

Thats a big help. Thank you for taking the time to write that up. Im going to move forward with that plan.

 

[RanchWelder]

Wow CalSgt, you just made my mind bend.

Just need to move my Gen 1 SBC forward with mounts to save my driveshaft relocation issues with my 4L80E swap.
Now I need to find some adjustable motor mounts or fab plates to move my engine foreward and use my 2 new electric fans from the K2500 parts.

My electric fan shroud is all ready to be cut out for the fan rig.

Might not have to cut my rear drive shaft or stretch the front drive line at all.

Measure Measure Measure, ...cut.

Finally a solution that gets my distributor an inch or 2 away from the damn firewall.

Electric Fans Rock!

These will work for my Gen 1, (they sell adjustable mounts for the LS swaps too):
https://www.dirtydingo.com/shop/index.php?cPath=348

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LS Conversion Mounts could help:
https://www.dirtydingo.com/shop/index.php?cPath=359

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* These mounts will clear low mount alternators but the amount of adjustment may be limited.


* Clears LS truck oil pan with a small notch on the driver side of the crossmember.

That is a lot of adjustment.

CalSgt!

 

[SquareDude]

Tejas Steelworks has a crossmember that works with the 6L80. I have done two. One with an NP208 and the other NP205. On the 208 I used the factory crossmember but had to make a bracket to bridge the gap between the transmission and the crossmember. In the 205 the Tejas mount was perfect location coupled with there engine mounts as well.

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[Craig Nedrow]

Tejas Steelworks has a crossmember that works with the 6L80. I have done two. One with an NP208 and the other NP205. On the 208 I used the factory crossmember but had to make a bracket to bridge the gap between the transmission and the crossmember. In the 205 the Tejas mount was perfect location coupled with there engine mounts as well.

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Looks real clean, and room for exhaust.