So this my first post and my first lsx build. I rebuilt and crammed the engine I drop it in get it to fire up but push on gas n does not wanna go passed 5mph n vibrates
its 5.3 attached to 700r4
I changed fluid n filled about 12 quarts so far.little history tho when I put engine in some how I dropped converter on floor spilling a lot fluid did not refill before putting back on
don’t know if I’m making since would love to fix on my own but not sure where to start
been going to this site for longest for help but this one problem I could not find on here exactly thanks in advance .

 

Unbolt the converter from the flex plate, push the converter as far back into the transmission as possible and start the engine. You may need to run the engine up a few 1,000 rpm and see if it still vibrates. If it doesn't vibrate then your problem is most likely with the converter, if it still vibrates then you have a problem with the engine.

 

Alright that was my plan to do today or tomorrow ill let you know how it goes thanks to the replay I hope its not the engine smh

 

Here’s a short clip on shifter in drives n I push gas don’t wanna go n feel my feet vibrate
tomorrow ima get under the car n look at converter

 

So I did what you said engine is ok converter bolts were loose but still didn’t fix problem so now ima pull trans

 

You may have bent the torque converter when you dropped it.

 

Thanks
Yah next task is to pull everything down hope its only that n not trans at all

 

I think this test should have been with convertor completely unbolted and pushed away from the engine, not just loose bolts. There should be a gap between the engine and converter.

 

I completely unbolted it and ran it
I was saying the bolt were loose when I went to check it
I pulled whole trans today anything I should look for see if everything is working properly
shops wont look at it they wanna rebuild
but ima go get torque converter looked at tomorrow

 

Did it vibrate in neutral as well as in gear?
Did it vibrate only when the car moved?
Did it make noise when running before or just vibrate? If it made noise as well, it may have been the loose flex plate bolts. If that was the case, the flex plate holes may have a telltale elongation. Might have been a good idea to tighten the flex plate bolts and do a check before you pulled the trans out.

While it's out I would check if the converter fits snugly into the crankshaft. Shouldn't be any play there.
Also check if the flex plate is cracked near the crank bolts.

The converter shop should be able to throw the converter on a balancer before they tear it down.

Keep eliminating each part of your setup until you nail down the part causing the vibration.

 

No only vibrated when I hit gas
yes vibrate a lot when I try to drive car wouldn’t go passed 5mph
not sure how engine ran before rebuild but car had 400 abc n drove fine before
i tighten the converter bolts when I seen them loose n gave it another shot n still same thing so that’s why I dropped trans

converter seemed fine all the way back n ima change rear seal this week n check flex plate

tomorrow going to shop n see if its converter 75$ for rebuild
I hope its that and not transmission it ran fine before but sat for 2 years

 

So got converter check guy said converter not my problem just had lil wear on shaft and inside had some aluminum shavings
so most likely my trans is my problem
trying to decide what to do maybe find another trans or rebuild mine just never have before but I’m up for the task the thing that kills me is buying the special tools ///😔😔
so ima sleep on it maybe go with th400 idk I do wanna make big power once I get this car rollin

 

The THM700-R4 transmissions are relatively "easy" to disassemble, clean, modify, and rebuild. Even for a first time transmission rebuild.
They also are not terribly expensive unless you are building for 700 - 1,000 HP (in that case a 4L80E is better and cheaper at same power level).

For a well thought out parts set and/ or individual replacement parts...
Dana from Pro Built Automatics is by far one of the best builders for these "Throttle-Valve" transmissions.
Dana is active on this message board, as member: "PBA". Also try him at: 909-795-1876 or probuiltautomatics.com

If you are in the New York City area in the near future; my shop also builds these transmissions up to 1,000 - 1,200 HP (Only when a 4L80E is not an option).
Otherwise my business specializes in GM power-train of all kinds from 1965 to present and GM vehicles 1955 to present...
For street and drag starting in the 1,000+ HP point and higher. Message me, should you be in the NYC area and I can be of service.

If you are going to rebuilt the transmission yourself...
Get yourself some snap-ring pliers.
Also you are going to need a transmission shop to disassemble the drums and maybe change the bushings.
Should you want to try this completely on your own...
Purchase a small press from a place like harbor freight ($130.00):



and a cheap clutch drum spring compressor off of Amazon or EBAY ($120.00):



Good Luck!

 

Slam a 4l80e into that thing. All the benefits of the th400 only with an overdrive

 

Yah see how the tools I need is gonna cost me few 100 $$ that’s what kills me for maybe a 1 year job
right now I’m looking for a low mile 4l60e and try that so I don’t have to cut my drive shaft
I might have found one out of ss Camaro but trying to do research on if it will fit my engine
its a lm4 aluminum block out of envoy lx I plan on running stand alone harness with my Fitech ls

 

So lil less stressed now lol got my transmission got 02 4l60e out of gbody suppose 96k miles stock
so question is what do I need to hook up any lil upgrades I should to it or should I change out filter or should I just hook it up n put fluid

 

Another question I have the Fitech system should I hook trans to that or get something better for tuning it

 

I'd try the fitech out first to see how that works with everything. Are you able to adjust different parameters with the trans control?(line pressure, shift points, converter lockup etc)

 

Why swap the THM700-R4 out for a 4L60E when you were trying to save money?
If you don't want to spend $200 - $300 dollars on a press and spring compressor...
What are your plans for getting a 4L60E transmission and torque converter. Not to mention tuning...

Both transmissions are essentially the same with the addition of the 4L60E needed electronic controlling.
Don't get me wrong... Most people would prefer the 4L60E over the THM700-R4.
However, you already have the THM700-R4... Seems like a lot of extra money spent for practically the same transmission.

 

Yah ima try the Fitech I guess all I need is lil harness extension to my system so ima go to the shop and pick up one they are local in riverside

well I think ima save money this way I paid 300 for trans it was out of his wrecked car plus now I can put my funds to a good converter witch is a new battle for me lol
but ima call yank I think this week see what they suggest I use with my set up then I should be on the road FINALLY