42rh strengh? Mods?

-
gregsdart

gregsdart

Well-Known Member
Joined
Jun 20, 2004
Messages
789
Reaction score
464
Location
mn
I am interested in moving to an OD 42rh trans to help drop rpm some with 3.55 gears. This 65 Dart is getting a 360 Magnum in the spring, and eventually a 392 Gen III Hemi down the road when funds permit. I have a 904 lockup (998 or 999?) that is available for parts scavenging.
I am not interested in going to a 518 trans, With the right mods, the 500 ought to hold up on the street and mild strip action.

P5060108.JPG
 
Hi gregsdart,
This FABO thread addresses the install of the 42RH in an A-Body.

42RH / A-500 in a Duster with pictures.

The thread doesn't answer your question about mods specifically, but the install is behind a magnum 5.9, so it does address strength somewhat. I would think that a rebuild with one of the many performance rebuild kits available for the 42RH would be plenty strong.

Travis
 
Great question!! I'm circling the Gen 3 rabbit hole, and seriously thinking about diving in but I was debating wether I want to go with a T-56 6 speed or a built 42rh. I'd need proof tho that the 42rh can be built to handle power since eventually I'd wanna install a Whipple supercharger on the 6.1.... So in short, I'll be keeping an eye on this thread
 
The 42RH is just a 904 with an overdrive on the back of it, so yes it can be built.
As it comes from OEM it is only capable of powering a 5000lb truck with a 5k tow rating.:D (sarcastic remark) :D

Serious power can be put through them just like the 904, and on my Dart I didn't have to mod the floor pan at all but just the trans cross member area top and bottom.
It was actually pretty easy to put in there.
 
"You do realize, you will need to do major floor, and trans cross member modifications"
Yep This was my first 65 Dart project
Dart pics + others 095.jpg
 
As far as the limits of the 904/42rh go, from what I understand I wouldn't want to push one over about 500+ to 600 ft lbs of torque. Torque is what will kill them. Boasted motors have a
BUNCH of torque.
 
From what I understand, the main trans is not a major problem. They have problems with the OD unit and the clutch in the converter. No personal experiance with these is a performance car.
 
75slant6 said:
Great question!! I'm circling the Gen 3 rabbit hole, and seriously thinking about diving in but I was debating wether I want to go with a T-56 6 speed or a built 42rh. I'd need proof tho that the 42rh can be built to handle power since eventually I'd wanna install a Whipple supercharger on the 6.1.... So in short, I'll be keeping an eye on this thread
Click to expand...

You may want to look at an Extreme Automatics Stage 2 or 3 200R4 with a Precision of New Hampton 3-disc lock-up high-stall torque converter. They are rated at 750 & 1000+ hp respectively, are more efficient to spin and are stronger once built than a similarly built Mopar O/D trans. It's one of the best transmissions I've ever had the pleasure to drive.

With a higher than stock stall and the lock-up converter, it's like having a five speed. I run a 3600 stall with the upgraded 3-carbon fiber disc lock-up in mine. It's lower 2.76 to 1 first gear and .67 overdrive make it an awesome street strip trans. Omit the lock-up converter if you are primarily into drag racing, as they add weight to the spinning drivetrain.

With 28 inch tall tires, 3.91 gears and the converter locked, I spin 2500 rpm at 80 mph. The 2.76 1st gear and 3.91's are roughly the equivalent of 4.30's out of the hole. I have to run Nitto Drag Radials to hook it up.

The torsion bar crossmember will need to be modified and US Cartool makes the trans mount, but the floor remains intact. Another nice feature is that you can swap the SFI rated bellhousings to fit small blocks, big blocks and Gen 3 Hemis. I used a Reid bellhousing and made my own crossmember pieces. One of the best things I ever did to my car!

Heart (Medium).png
 
JBC, the 42rh would be more budget friendly for me, as I can do my own tranny work. Precision also makes a multi disc lockup converter for the A500, and a spacer to make room for it as it is a thicker converter. Sounds like I have good options, just need to learn more about valve body mods, max clutch setups, and how to oil that OD unit better. I hear that is the big problem with the OD?
 
You must log in or register to reply here.
-

Back
Top