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GM Gen 4 conversion including LS

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conversion
963K views 3K replies 280 participants last post by  LandDefender 
#1 · (Edited by Moderator)
O.k. I got permission from the forum member to post a few pics.

This is a GM Gen 4 mated to a 6 speed and then to the LT230. Guess what...no change needed in your drive lines as this mates up to your LT 230.

Imaging all the HP and gas mileage you could want. WOW. More to come from the forum member.
 

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#626 ·
Top speed wasn't my concern at all. Just popped up when I ran the calcs. Made me laugh. No way in heck I'm taking a 110 over 100 mph. :thumbs

Your 6th gear overall drive is 2.75, turning 35's. About the same as running the 1.22 high range with 3.54 diffs (2.88), but with taller tires. Hmm. By changing to 1.003, with 33's, and 3.54 diffs, 6th gear is over 80 mph at 2000 rpm.

The good news is I'll have a 110 and D1 tcase to choose from. Still up in the air on what size tires I'm going to run. If I do decide on 35's, pretty sure I'll go with the 1.22. That would be 2100 rpm at 75, which is the highest limit in CO anyway, but I should be in the power band enough that the steeper climbs up Floyd Hill, Eisenhower, and Vail Pass won't be lugging the motor.

I'm glad you spoke up though. The numbers feel pretty meaningless without some first-hand experience driving it.
 
#627 ·
The top gear should be set to work on the flats at constant speed, for maximum efficiency. It then shifts down for hills and accelerating. Top gear should never be chosen for climbing.
 
#628 · (Edited)
Jonathan, you could compare the gear ratios and engine power to your LR4 to get a frame of reference. They probably have about the same "resistance" at highway speed (LR4 a little sleeker, 110 a little lighter).

LR4 ratios

1st: 4.17
2nd: 2.34
3rd: 1.52
4th: 1.14
5th: 0.87
6th: 0.69

Transfer case high range 1:1, low range 2.93:1

Diff ratio: 3.54

30" tall factory tire

LR4 5.0 V8 is 375hp/375tq

Anyone who has driven an LR4 knows how magnificent this powertrain is... an LS/6L80 swap would basically emulate it in a Defender :)
 
#629 ·
What is "normally" done to proper size the final drive.... Work out the power required to move the vehicle versus speed. Find out the wheel power available versus speed. Decide on a maximum speed you want to be able to maintain, on the flat, with no wind without dropping down a gear. Plot and adjust final drive to suit. This gives you the best mileage.

I suspect with this engine, you can't go high enough on the gearing.

Like this:
 
#644 · (Edited)
What is "normally" done to proper size the final drive.... Work out the power required to move the vehicle versus speed. Find out the wheel power available versus speed. Decide on a maximum speed you want to be able to maintain, on the flat, with no wind without dropping down a gear. Plot and adjust final drive to suit. This gives you the best mileage.

I suspect with this engine, you can't go high enough on the gearing.
So I had played around with a curve for the 2.5 NA yesterday and thought, why not plug in the GM engine...... So with the 1:1 high range, you will be able to do 100 mph before needing to shift down.... Top speed in 4th around 130 mph.

edit: added the 6.2, LS3. Say 105 mph before shifting down and 140 mph top speed.
 

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#634 ·
As I explained earlier the higher the gearing the better for efficiency. There is no way to have gearing that is too high with that much power and the options available. Should run a 1.0 high range.
 
#635 ·
I believe the 1.003 high range gears are still available new... hopefully they are not just limited supply NOS. As this conversion continues to build momentum there will probably be a strong demand.

By the way, on a slightly different note... the ultimate LT230 would be 1.003 high, 49% reduction (5:1) low, and limited slip center diff!
 
#658 ·
Has anyone looked into what's required to water-proof these engines, or improve their fording depth? I know the obvious stuff like copious amounts of dielectric grease, mount computers high as possible, etc. But, more specifically, issues associated with this motor swap.
 
#659 ·
I think you've answered your own question there, the quality of connectors used on both the sensors, coilpacks & ECU are far superior to those used on older LR Lucas systems. They all have silicon seals between the connector halves & on the wire entry too. Keep the water out of those with some grease, your air intake pipe work sealed & above water and you should be golden. Switch out the dipstick to a flexible sealed cap type for some extra security and make sure any breathers are well up out the way.

Check out what some of the mud boggers do with LS motors.... :rolleyes
 
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