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List, step-by-step, all steps necessary to run a TH-350 behind an LT engine.

vandelay industries

vandelay industries

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Please list, step-by-step, if it's even possible, what is needed to run a TH-350 (non-lockup) behind an LT engine. This is the newest gm engine, not the LT-1 engine found in 70's corvettes camaros etc.

Also, this is LT, not LS.

The more detail the better.

This may be the best solution for me in terms of time, easy-ness. (LV3 v-6) i'm like the opposite of Smokey Yunick.
 
Fastereddie said:
Step 1. Don’t.
You'll be miles ahead to run the trans that belongs behind it.
Click to expand...

I'm open to it, but how much larger/heavier is the 6L80 (or whatever 6 spd comes with the LV3 4.3) compared to a TH-350. AND, won't there need to be a switch on the brake pedal to dis-engage the torque converter? Or is there another way to control this? See......complexity already. That's one reason why i'd like to stick with the TH-350.......
 

Chevrolet transmission dimensions, gear ratios and oil quantity

Chevrolet transmission information - dimensions, gear ratios and oil quantity
non-stoptransmission.com non-stoptransmission.com
That shows some dimensions.
I know it will bolt up minus one bolt that doesn’t line up. You’d need an ict billet converter hub spacer. The th350 is a 3 bolt converter, not sure if that pattern would line up. I know the th400 does.
 
Yeah, i'm suspecting i would need either the hub spacer and/or a different flexplate or different converter. i think the engine to trans bolts are now metric, no big deal....

The 350 and 400 torque converters are interchangeable, at least the ones i use.
 
According to Novak website----TH-350 about 70-90 lbs. lighter than 6L80. But i'm not even concerned about weight first and foremost. i want something that just works and is straightforward.

i'm really not that good with engines/transes right now.
 
Not all the same flex plate. Early LS style is different

And I would second or third or fourth the “run the 4L or 6L style behind it
No sense reinventing the wheel
 
Bent77 said:
Not all the same flex plate. Early LS style is different

And I would second or third or fourth the “run the 4L or 6L style behind it
No sense reinventing the wheel
Click to expand...

That may be the easiest way; If i have to put a switch on/near the brake pedal arm (?), this should not be a big deal?
 
Bent77 said:
Not all the same flex plate. Early LS style is different

And I would second or third or fourth the “run the 4L or 6L style behind it
No sense reinventing the wheel
Click to expand...
Hey..........wait a minute! i think you know more than you're letting on.

Seriously, i need step-by-step VERY DETAILED instructions here. i'm really not good at this.
 
vandelay industries said:
That may be the easiest way; If i have to put a switch on/near the brake pedal arm (?), this should not be a big deal?
Click to expand...
You already have a switch on the brake pedal, it's for the brake lights.
There are many ways to do it.
I third the newer transmission.
I am trying to figure out how to put the newer trans on an older engine, to eliminate the TV cable
 
Yep, take advantage of the technology. As free revving as the LT platform is why would anyone want to saddle it with a non-od 3-speed with a crappy 2.48 low gear? There's a reason they are usually equipped with the 6, 8, or 10 speed transmissions with really deep gears.

I don't think anybody has a full blown step by step list of instructions for any of these swaps. Because of the variables involved between the target vehicle engine and trans being so wide not every swap is the same. But reviewing others builds will give a good idea of the work involved.

Like most of us that have swapped one, part of the process is research. Not just here. You are adding complexity with the newer engine alone adding in the trans is not much more. The computer runs them both. You just need to deal with the added size for the trans for mounting and floor pan clearance.

One other thing about the th350 is where the kickdown cable is going to hook up too. The LT engines are all drive by wire throttles. Unless you switch to an aftermarket cable throttle or modify the trans to not need the kickdown cable the use of the th350 isn't a snap.
 
@Fastereddie installed a TH400 with my Gen V swap and at the time I didn't have the scratch for the 6L or 8L or the correct transfer case. Looking back now and where am at, I really wished I just went for the correct setup the first time. As it is it's working perfect but would benefit from the newer auto.

Just get the correct trans for your newer engine.
 
Not sure if this is still relevant or not, but a hub spacer like mentioned above is needed to seat the converter / pump to the crank snout. The flex plate to converter bolts will be close but not right. You will have to wollow*..? out the holes a 1/4 inch or so to get them to meet. I agree with all the above that a th350 with no OD would suck for an engine with that much potential. You will also be missing a few bellhousing bolts like also mentioned. I went through all these options when i did my swap. I opted out for the cheapest 4l60e i could find for now, the gearing is much better and OD... and it was only a couple hundred bucks more for a used one than a th350.

That being said, my good friend was running a stock th350 behind an LS with 10-14 Lbs of boost and it held up for a year... the thing really only did burnouts though, so i wouldnt suggest going that route for long term good drivability.
 
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