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A couple weeks ago I wiped a cam lobe (#5 exhaust) in my 270hp/350 71. There was a Lunati cam in there and maybe it wasn't set up right. Simultaneously on the same day and on the same trip that I was almost stranded due to the failing engine, my TH400 also stopped shifting out of 1st. It seems like it might even try to shift out of first and then into neutral. Wow, such luck! Simultaneous engine and trans failure!?
The failed cylinder #5 in the motor is severely scored with cupped lifter, all intake valves are caked with piles of carbon and the inside of the manifold is wet/oily. Actually all cylinders are scored but #5 is the worst.
Working in my garage on jack stands, I will be removing the motor to drop off at the builder. I guess I should also remove the trans to drop off at the trans shop. I am seeking advice on how to remove the trans when on jack stands (I would love it if someone could inform me that maybe the trans is not shifting cuz the motor was failing and vacuum was messed up.... the simultaneity of all this is perplexing):
1. How high do I have to get the car up to be able to slide out the TH400? I am looking at purchasing a motorcycle jack or trans jack to help with the removal, but concerned about clearance to get the trans out from under the car while resting on the jack. I don't want to do the floor jack balancing act if possible. 2. What are the best locations for the jack stands? Is it OK to use jack stands at the front of the frame rails at the sway bar mounts? I don't want to bend or crush anything, but need to be able to slide the trans out.
Thank you for your help!! Tight quarters in my garage are preventing me from the simultaneous motor-trans extraction.
From jackstands, it was a simple matter to remove the trans crossmember, disconnect everything, and pull both the L48 and TH30 together. I used a gantry crane from harbor freight, outside on concrete, so I had plenty of space. Prep in the garage, and my outdoor time may have only been an hour or two.
YMMV, but it seemed pretty easy. To get everything out, at least.
I’d suggest four 6 ton jack stands to be high enough and steady enough to wrangle the transmission out. Maybe have them at the four frame corners below the cabin, in front of rear tires and behind the front tires. Use a transmission jack with a chain or ratchet straps securing it. TH 400s are heavy and gravity works well on them. You can slide the transmission off and on the jack to get enough height to slide out from under the car. This would be a good time to make the transmission crossmember removable.
Make sure you don’t have a vacuum leak somewhere in the modulator line. Or a bad modulator. Pull some vacuum with a hand held pump to test. I’m sure the rebuild for a TH 400 isn’t $350 like 1990’s. And then there’s the cornvertor….
Thank you all for your responses. I need to think this through before diving in, because I am not an expert. Safety for me and also the fiberglass is weighing big.
I am planning on obtaining the 6 ton jack stands, I think they lift to about 23 inches. Harbor Freight does have a scissor style trans jack with a strap, but not enough info for me to determine if I can get it out from under the car with trans on board. Maybe i'll hit Harbor Freight this afternoon with a tape measure and check it out.
I also still have to consider pulling the trans with the motor, but I will have to roll the car around to a flat area with enough room...
Thank you all for your responses. I need to think this through before diving in, because I am not an expert. Safety for me and also the fiberglass is weighing big.
I am planning on obtaining the 6 ton jack stands, I think they lift to about 23 inches. Harbor Freight does have a scissor style trans jack with a strap, but not enough info for me to determine if I can get it out from under the car with trans on board. Maybe i'll hit Harbor Freight this afternoon with a tape measure and check it out.
I also still have to consider pulling the trans with the motor, but I will have to roll the car around to a flat area with enough room...
I have this exact trans jack, just got it for my upcoming differential removal. It is 7 5/8" tall fully compressed at the highest point on the outside of the mount plate. With a Harbor Freight low profile jack, I can only get my 6T jack stands to 19 inches when lifting both tires at the same time from the rear. Sorry for your loss.
Last edited by USMC6113; Jan 15, 2025 at 05:41 PM.
From: At my Bar drinking and wrenching in Lafayette Colorado
Just pull the engine and tranny as a unit - it's silly to drop the tranny out the bottom and then pull the engine out the top - it all comes out in one piece - piece of cake. Here are photos of me doing it to a supercharged Vette with a Tremec 6-speed on it, which is bigger than a TH400. I just put a floor jack under the tranny tailshaft housing to adjust the angle and to follow the tranny as it moved forward and up. The car isn't even on jack stands:
From: At my Bar drinking and wrenching in Lafayette Colorado
You don't have to raise the car off the ground to pull the engine & tranny together. You only have to get under the car to unhook/unbolt everything (driveshaft, shifter cable, exhaust), and then pull everything out with the car sitting flat on the ground. No need for ramps or spacers.
Lars, thank you for the excellent photo series of the motor/trans extraction! It looks like the core support is removed, and I was wondering about that. Congratulations on engineering the Paxton motor and Tremec into those tight quarters. I wish I had you as a neighbor. All I have is neighbors who know how to pressure wash their Teslas. And we are not on speaking terms....
DanielNiclas
I have removed and installed my Muncie m21, Richmond 6-speed, and 200-4r with the car on ramps. So whatever regular tire ramps height is would be enough to R&R a tranny.....the manual are really small.... as far as the 200-4r I could slide and tilt to get it out from under--- I suppose your thm-400 would be somewhat like that.
I remember lifting my Muncie and Richmond up with a contraption I welded up to bolt onto my jack and then getting under there and pushing it up by hand...... but the last couple of times I could not imagine being able to do it.
Since I have a convertible the last couple of time I used the engine hoist and chain wrapped around the tranny and then coming up through the shifter hole ...... I was able to lower it all the way to smooth concrete floor..... and that was through the small manual tranny shifter hole. The shifter hole is bigger now for the automatic so it was easier to rig to the hoist when I last lifted the 200-4r to install it..... now so should be easier to lower next time I do tranny experiments.
From my understanding poor vacuum control will affect the THM trannies. If there was nothing wrong before your engine failed you could always check the tranny after the engine is fixed.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by carriljc
I have removed and installed my Muncie m21, Richmond 6-speed with the car on ramps. So whatever regular tire ramps height is would be enough to R&R a tranny.....
That's because the manual trannies can be pulled out without the bellhousing attached. When you pull an automatic with the bellhousing integral to the tranny, and have the tranny sitting on top of a floor jack after it's out of the car, you can't get the tranny and floor jack out of the tranny tunnel due to the height of the bellhousing not clearing the floorboards and frame of the car without the car sitting very high up off the floor - higher than most jackstands will allow. Your option becomes to push/tip the tranny off the floorjack once the tranny/jack is fully lowered in order to get the tranny onto the garage floor and then slide it out from under the car. Or, get the car up so high that you can get the tranny out from under the floorboards and frame. That can be a pain. So just pull the entire engine/tranny out the top in one piece with the car on the ground. It also makes the mating of the engine/tranny/torque converter (or tranny/clutch) a lot easier when you assemble it all on the shop floor out of the vehicle. Then, just slide the entire assembly right back in. The engine/tranny assembly can be pulled out of a Vette from the top side in less than 2 hours. You'll spend more than that screwing around trying to drop just the tranny out the bottom.
I did the 200-4R with the car on ramps also.
He says he's limited in garage space so I'm just letting him know that it can be done.
The auto tranny can be gently slid off whatever support/jack you have underneath it. I've done it.
TH400 Removal/Install on Jacks
