Ls swap motor mount and clearance questions

[WickedDirtBag]

Ok guys finally got my 5.3/4l60e combo. Pulling 350/350 combo out. Do not want to change out driveshaft or drill crossmember. If I read correctly the new trans is 1.5" longer. So I want to shift the whole shebang forward to get the trans mounts in place. Will I have clearance issues with stock fan and which mounts do I need to purchase to achieve this. I have low budget so inexpensive mounts. Oh and I don't want to change motor mount towers either. Thanks guys can't wait to get it up and runnin.
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[truckdude239]

I used the dirty dingo 3 inch slider mount on mine and with it all the way forward my driveshaft was still to long so i slid it all the way back and shortened my driveshaft 6 inches

[71chevystep4x4]

You'll probably have to modify something along the line, it's just the nature of this kind of swap. I was sure that I wouldn't have to change anything being I ran a small block and big block using same mounts, crossmember and location, but was I wrong. NOTHING fit according to what everyone else said, and I ended up changing a little bit of everything. The end result is very rewarding. Good luck

[BR3W CITY]

Originally Posted by WickedDirtBag

Ok guys finally got my 5.3/4l60e combo. Pulling 350/350 combo out. Do not want to change out driveshaft or drill crossmember. If I read correctly the new trans is 1.5" longer. So I want to shift the whole shebang forward to get the trans mounts in place. Will I have clearance issues with stock fan and which mounts do I need to purchase to achieve this. I have low budget so inexpensive mounts. Oh and I don't want to change motor mount towers either. Thanks guys can't wait to get it up and runnin.
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With how many times you tell us that you DO NOT want to do this or that, it seems like you DO NOT really want to invest ANYTHING into doing it. I get being on a budget but cmon. Why not move or drill the crossmember?

some scenarios
v1. If the new trans is 1.5" longer, you'd have to shorten the driveshaft by that amount ~$150, assuming the engine sat in the stock place on sbc->lsx adpater plates ~$45 (Which would leave you enough room for the stock clutch fan)

v2. IF you don't shorten the shaft, then you have to move the engine forward approx 1.5". Some cheap and diy adapter plates will move it about that much, though depending on the application, you might end up looking at the more expensive slider mounts or POL mounts from $100++. This also takes away space for the clutch fan unless you have a crazy thin radiator. Adding an e-fan even a used for junkyard piece is ~50-250+ .

In either situation, the later model trans may not use the exact same rear trans mount style....my 3speed->700r4->4l80e changes used different mounts. This also changed where the crossmember had to sit, seperate from the expected difference in length.

Why are you so against really changing anything (yet putting a different motor in)?

[WickedDirtBag]

Not really against modifying anything. It's my daily driver so I was looking for the quickest and most cost efficient. Personally willing to do what it takes to do it right, financially have to keep it within reason. From what you guys are sayin looks like movin crossmember and shortening drive shaft is the clearest option. Done deal. Just hoping to plug and play. So excited just wanted to drop it in and rock and roll!
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[JMac11]

Did not measure to compare, but remember that the LS engines are shorter on the back end. I put a 700r4 behind the 350 and moved the engine forward the 1.5 inches. Now that I have put the LS mount in for the K5, it seems that the motor is closer to the firewall, so overall it was a wash. The LS engines do not have as much block hangover on the rear of the engines......

[BR3W CITY]

Moving the crossmember takes 20 minutes and a step drill, and is by no means hard, though for sake of ease I actually waited till my engine was on the mounts before modifying the xmember.

I took the old trans mount off, replaced it with a block of wood to estimate tail height at 3* down @ engine, then slid the mount into place under the trans. I re-drilled the frame holes, then came back and drilled the center holes for the mounts.

As for the driveshaft, just print the worksheet that the DS shop gives you (or you can find one online). It'll give you the measurement points and yolk styles, just tell them what ya need. If you plan to drive it daily get non-hd u-joints which can be greased, if you are worried about strength, get the no-zerg HD u-joints.

[Blackpony]

I used 1" set back plates and drilled holes for the cross member to be moved and the trans bolt up. With that I was able to use the stock drive shaft, stock shifter linkage etc. everything bolted right up with new grade 8 hardware and all is well. Hope this helps!
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[Blackpony]

Oh and I bought my adapter mount plates for the engine off eBay for $50. They allow forward 1", stock and setback 1".
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[solidaxel]

Originally Posted by Blackpony

I used 1" set back plates and drilled holes for the cross member to be moved and the trans bolt up. With that I was able to use the stock drive shaft, stock shifter linkage etc. everything bolted right up with new grade 8 hardware and all is well. Hope this helps!
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When you moved the x member did you use the two 45* upper brace to x member brackets?

[Blackpony]

Mine only had one on the passenger side and no I did not reuse it. Thus far no issues so I sure it's fine. Maybe one day I will be able to pull the cab for a resto and ill put it back on then.
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[Robznob11]

you do realize shifting the engine forward 1" drastically changes the front/back weight ratio and decreases driving performance. scooting back always helps. I would not make it drive like a pig just to save a few bucks. just my .02

[WickedDirtBag]

Actually was thinking about the weight ratio issue last night. In the long term i want this truck to be a good all arounder. Solid braking. well above average suspension. clean reliable horsepower. My biggest problem is budget and patience. Can't wait to spend every penny possible!

[solidaxel]

Originally Posted by truckdude239

I used the dirty dingo 3 inch slider mount on mine and with it all the way forward my driveshaft was still to long so i slid it all the way back and shortened my driveshaft 6 inches

So where is the transmission mounted now in relation to the existing (old) rear motor mount, how much to farther to the rear did the new package end up?

[truckdude239]

mine for same reason moved the trans back member back about 4 inches but i ended up with 6 inches taken out of my driveshaft

[solidaxel]

Originally Posted by truckdude239

mine for same reason moved the trans back member back about 4 inches but i ended up with 6 inches taken out of my driveshaft

Did your transmission linkage to column need to be modified?

[Blackpony]

Here is what my truck weighs as it sits right now. Aluminum 5.7, moved 1'' back, 4l60, etc.

[Blackpony]

And here is what it weighs with me sitting in the truck. Oh btw this is same day with about 1/2 tank of fuel

[truckdude239]

No the stock linkage worked juzt fine for the gear shifter
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[solidaxel]

Originally Posted by truckdude239

No the stock linkage worked juzt fine for the gear shifter
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Thanks for the info.

[solidaxel]

Originally Posted by Blackpony

Here is what my truck weighs as it sits right now. Aluminum 5.7, moved 1'' back, 4l60, etc.

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How much difference would it make with 2" to the rear make, any idea?

[Blackpony]

Not sure if you can go 2" rearward. At least with my truck there is only about 1/2" between the exhaust manifold and the firewall.. But going another inch will probably move 15-20 lbs rearward if I had to guess..
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[solidaxel]

Thank You, We will see if I can get it back one inch

[Blackpony]

The only reason I went 1" setback was to keep the trans in the stock location so no modification was required with the th350 I had before. I am now looking at putting it back to the stock engine location and moving the shifter stuff up a bit and getting a longer front yolk for the driveshaft so everything will hook back up. That will allow me to use the stock ac compressor and rid of the power robbing r4 style I have now. I lose about 3 mpg with the ac on due to the parasitic drag the compressor has. I'm hoping the stock unit will be more efficient as I have been told it is so I can gain a few mpgs back.
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[solidaxel]

The guy at D Dingo said to adjust the motor mounts to fit the stock drive shaft, and the linkage would be in the right position.

He sells parts, so I just question everything until I have tried it!

You folks have a better feeling for the end results.
Thanks