Fitting a 42RH in a B-Body?

[halfafish]

Something took a dump in the trans for my 72 Coronet wagon. I was out for a spin and all was well. Then trying to go from a stoplight, no motion at all. No noises, no slippage, it just stopped going in either direction.

My longterm plan was to put one of the overdrive units in the car anyway to replace the 904. Looks like the time may be now. Has anyone fit a 42RH in a similar car? Im wondering if there are any mods needed to fit it in.

 

[1 Wild R/T]

72 B body is the same floor pan basically as an E body... It should fit with minimal problems... Trim the transmission case and leave the car body as is.... The fixturing tabs on the O/D need to be removed, the webbing near the speedometer has to be removed.. Driveshaft will need to be cut.. Shift linkage & kickdown linkage should bolt right up....

 

[1 Wild R/T]

If you lack fab skills USCT sells a crossmember, it's designed for a 518 but the area where it mounts is the O/D section & that is the same whether your dealing with a 500 (RH42) or a 518 (RH46)

USCTAM2029-70 - 74 E-Body, 71-72 B-Body 518 Crossmember Kit

 

[halfafish]

Excellent info, thanks! I have semi-capable fab skill but would probably get the USCT unit for simplicity's sake.

 

[1 Wild R/T]

I'm thinking the 42 is about 1/2" shorter than the 46... The speedometer cable is ridiculously close with the 46... You might need to use a gps speedo or get really creative to run the cable..

shift control... .
Options for Overdrive Auto Trans - Ebody

 

[halfafish]

Good news, this project is now moving forward. It took a while to find a core trans and then get it rebuilt. The completed candidate is ready to go with a rebuilt torque converter. I did get the US Cartool crossmember to simplify my install.

The fixturing tabs on the O/D need to be removed, the webbing near the speedometer has to be removed.

@1 Wild R/T, you mention the fixturing tabs, what exactly are those? I see these two wing-looking things near the tail that look to be likely candidates for a trim job. Are these what you're talking about?

 

[Paul_G]

Ive done a few of the 46RH swaps. All in B Body cars. Sometimes the floor just needs to be hammered out some, sometimes the pinch weld at the front of the floor and firewall needs to be rolled, The trans will need to be trimmed as stated. Plan on putting the trans in and out several times before you get the floor and trans to fit just right. No getting around it. You have to get the trans high enough in the tunnel to get your drive shaft pinion angles right. If you dont you will have vibration issues forever unless you drop the trans again and clearence the floor to get it high enough.

Put it in and out without the converter till you get it to fit. Best case is to fit the trans with no internals, makes it lighter.

 

[halfafish]

Put it in and out without the converter till you get it to fit. Best case is to fit the trans with no internals, makes it lighter.

Good ideas, thanks. I planned to skip the TC until final assembly, but the trans is already built. Wish I'd heard of this earlier, I could have gotten the empty case for a while to do the fab work but alas it is not to be.

Let's revisit the trimming issue. I took a better look at the case and I see a number of things that look to be likely candidates for removal. Can anyone confirm? If nothing else I guess I'll figure it out when I start test fitting. Here are additional things that could interfere with the tunnel.

I don't think these are needed on the passenger side.

And here are a couple on the driver side.

 

[Paul_G]

I will attach some pics of my 46RE mocked up in the 72 Sat. The trans is out for rebuild right now or I would show it. . I did the testing with no internals, just lifted it up and down for mock up, about 2 dozen times.

 

[Paul_G]

I had to cut the floor support and weld in a plate. The drivers side inside bolt was too close. I drilled a new bolt hole in the floor crossmember, welded a pipe in for strength. Then welded a nut in what was left of the orginal hole to have 3 bolts on the drivers side. I also modified the stock trans mount cross member myself. Also, keep the trans centered in the tunnel, off to the left or right will cause pinion angle and vibration issues.