Torque converter bolt confusion

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JohnIL

Greasemonkey
Sep 9, 2020
124
63
Central Illinois
I'm trying to bolt a 4l60e to an 5.3L LS Engine in my son's '83 El Camino. The next step is to install the torque converter bolts, but they don't fit. The transmission and torque converter where bought as a "take out". I don't know what year of vehicle they came out of. The ARP bolt kit I bought says it is specifically for a 4l60e. The bolt kit is part #230-7304. The bolts are metric, size M10 x 1.5. The bolts will go in about 2 threads, then they stop.

Here's the confusing part. In my stash of old stuff, I had a set of 3/8-16 bolts from an old TH350 transmission. They appear to fit perfectly. What gives? The 3/8 bolts will thread all the way, but I'm afraid to torque them down. I don't want to take chance on damaging the threads in the torque converter threaded bosses.

So, the question on the table is, did they ever make a 4l60e torque converter that used 3/8" bolts instead of M10 bolts? Am I missing something? Thanks for any advice you can give.

John
 

JD1964

Master Mechanic
Dec 31, 2014
273
63
First, since you don’t know the actual source or history of the transmission I would make sure the converter actually matches the transmission.

On the 3/8” bolts, when you have them threaded in but not fully seated, are the bolt shanks snug in the holes without and side to side wiggle? If so I’d say they fit properly. I would use loctite on them.

If you have the correct converter then good. Next important thing is the depth of the pump drive and spline in the transmission. That can change when mating transmissions to engines that they didn’t normally come with. Make sure you research and get that correct too.
 

JohnIL

Greasemonkey
Thread starter
Sep 9, 2020
124
63
Central Illinois
Mystery solved! I pulled the transmission back out of the car this morning so I could verify the identity of the torque converter. It's a GM 92 (Code TMBX) with a 1400-1600 stall. It does indeed use M10 x 1.5 bolts. The problem was that the APR bolts appear to be slightly oversized. I'm guessing there is some sort of coating, but it caused the bots to jam. I solved the problem by picking up $1.29 worth of new grade 10.9 bolts from a local farm store. These bolts fit perfectly. The transmission and torque converter when back together with no trouble.

John
 
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