Click on image for the lowdown. 
====
| | | Forums66 Topics128,035 Posts1,055,559 Members48,426 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Dec 2015 Posts: 2,062 Big Bolt Forum Moderator | | Big Bolt Forum Moderator Joined: Dec 2015 Posts: 2,062 | Anyone here running one? Here is my question:
I have one I am going to install in my 58 6400. I have the stock cast-iron V-8 bell housing and mounts on the front f the engine and the bell housing. Adding the overdrive will move the SM420 back 7 1/4". Do I need to fabricate a cross member for the rear of the trans, or will it be fine hanging off the bell housing being farther back?
| | | | | Joined: Feb 2004 Posts: 29,760 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,760 | Better safe than sorry- - - -that SM 420 is a HEAVY transmission. I'd be more concerned about torque loads on the bellhousing than weight, but either one could break the bellhousing under the wrong operating conditions.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | What do the instructions say about the Ranger, do they recommend an extra transmission mount in your application? It's possible too that adding another mount may overly constrain the engine and transmission to the flexible frame, then causing vibrations at best or broken mounts and bell housing at worst. If more support is necessary design the new mount such that it carries the weight but does not influence location. A factory example is Roadranger transmissions are long and very heavy, the 10 speeds don't usually have extra support, but the 13 and 18 speeds may. They commonly use a leaf spring transverse to the frame to share the weight. Here's a pictureI've seen and heard of these troubles with vibration and broken stuff in diesel conversions where the well meaning installer adds more mounts for the "bigger and longer" drivetrain without understanding that the engine and transmissions are stiff, and the frame flexes. Grigg | | | | | Joined: Feb 2004 Posts: 29,760 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,760 | Any add-on mount should include some sort of rubber isolator to avoid transferring driveline vibration and noise to the frame and/or cab, and allow for a little flex.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | Yes, but still possible to cause trouble depending on how stiff the rubber is. | | | | | Joined: Dec 2015 Posts: 2,062 Big Bolt Forum Moderator | | Big Bolt Forum Moderator Joined: Dec 2015 Posts: 2,062 | causing additional vibration is my concern. When I had my golf car business, I had 2 main suppliers of parts. They both carried motor mounts for E-Z-GO gas golf cars, one supplier, was great, the other, if I got their mounts, they felt like I had put in solid steel, it vibrated like crazy! It was all because of the compound of the rubber. | | |
|
|
