4l70e

[Grandad68]

New member and first post! After many, many years of working on early Chevy V8s, I finally moved to the LS series by purchasing an LS376 with a 4L70E Connect and Cruise package. My 17 year old grandson and I are installing it in a 1968 Camaro. But, I'm afraid I may have already made a mistake when installing the transmission to the engine. I partially filled the torque converter with ATF and installed it on the transmission with the required two steps. I measured and had the required amount of backspace. This was my first experience with a torque converter with a snout that fit into the crankshaft. I'd done many manual transmissions that did and even torque converters with no snout. I cleaned both the snout and the crankshaft and lightly greased them before moving the transmission into place. It seemed to go in fine. I put all the bellhousing bolts in finger tight and then used a wrench to snug them up (less than 5 ft-lbs) with an even gap to the block, leaving about 1/4" so I could observe the flexplate. I then put a torque wrench on the crank bolt to turn the engine to line up the converter to the first of the three flexplate bolts. Took over 100 ft-lbs to move the engine. This seemed high but it was a new engine and I’d never turned an LS3 engine. I moved one flat on the bolt and turned it again. This time I heard a loud pop and the torque converter rang like a bell for about 2 seconds.

I first thought that I had slightly preloaded the converter snout when snugging the bellhousing bolts, and it had popped into place. However, I then noticed that the engine would turn with something under 50 ft-lbs. This made me think I broke something in the converter or the transmission. So, did I break something? If so, how do I determine what? Thanks in advance for the advice.

[pajeff02]

Welcome to the site.

That does not sound good -- if I recall, the torque converter has at least two "steps" as you spin and slide it onto the input shaft. I have a vid on Photobucket of my torque converter installation, but thanks to Photobucket's recent bout of stupidity I cannot post it here. Nothing should make a loud pop like that and I agree that the engine should spin over a lot easier than it did. Back apart?

[Grandad68]

Thanks for the reply! I had the two clicks just as recommended. Everything seemed fine and the backspacing from the bellhousing was correct. Back apart is certainly the first step if I don't receive other advice. However, I have no clue what to do if I don't see something visual after that. Thanks again.

[pajeff02]

You will want to carefully inspect the pump engagement tangs for any apparent damage. Did the torque converter come with the transmission?

[Grandad68]

Yes, it came as part of the Connect and Cruise package. It's a GM product. I will inspect both the snout and the pump engagement tangs this weekend and report.

[pajeff02]

Fingers crossed.

[Grandad68]

You were right on the money pajeff02. I first inspected the snout and crankshaft pilot hole. Couldn't find so much as a scratch on either. Then inspected the pump drive tangs and discovered what my pop was. I had a calculated clearance of .200" between the converter and the flexplate. I then left the bellhousing about 1/4" (I didn't measure this) from the block before turning the engine to line up the converter bolt holes. That allowed the converter to move out at least .450". This is about the depth of the straight part of the drive tangs. I still haven't determined how I was transmitting torque from the crankshaft to the converter but I apparently was. The chamfer on the top of the converter was slightly rolled and the tangs in the transmission are also. Both appear to be about 1/32". Now I have to decide what to do next. Everything fits together well and no noise when the engine is turned over. Very tempted to use as is but would much rather fix something now than later. I would appreciate any advise on this. I can send a picture if you'd like. Thanks in advance!

[pajeff02]

Glad you have it figured out. If all it did was slightly chamfer the edges you may be ok. If you have a reputable trans shop in the area they may be able to take a look at it and give you their .02 on it.

[Grandad68]

Thanks again for more good advise pajeff02. I did have one idea I might try before going to the transmission shop. Is there a torque specification on the pump drive? I could measure the torque required to turn the fully installed converter if it might give the specialist more information.

[pajeff02]

Not that I know of.