Click on image for the lowdown. 
====
| | |
0 members (),
149
guests, and
2
robots. | | Key: Admin,
Global Mod,
Mod | | | Forums66 Topics128,113 Posts1,056,619 Members48,450 | | 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 2007 Posts: 171 Shop Shark | | Shop Shark Joined: Dec 2007 Posts: 171 | Does anyone here have any knowledge of the auxiliary Chelsea overdrive box? I have a chance to buy one but would like to know a bit more before I decide to buy it. This box mounts mid-ship in the drive-line.
Al | | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | I've not seen/heard of one of that brand, sure would like to see it.
In general auxiliary transmissions are good and neat things. Take a little effort to install properly but not tricky.
Some are quite large, not suitable for a smaller truck, be sure it'll fit first. | | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | Did a little searching and someone said the Chelsea auxiliary transmissions were recalled, not strong enough... May or may not be true, I don't know.
Pretty sure it is uncommon though, which means hard parts are hard or impossible to get. Bearings and seals should be getable. | | | | | Joined: Dec 2007 Posts: 171 Shop Shark | | Shop Shark Joined: Dec 2007 Posts: 171 | I have completed a bit more research and have determined that this aux. overdrive may be called either a Dana or Chelsea.!? I think it is a 25% overdrive. I does not appear to have a neutral only a direct and then directly to overdrive.
Al | | | | | Joined: Dec 2007 Posts: 171 Shop Shark | | Shop Shark Joined: Dec 2007 Posts: 171 | I have a bit more information on this aux. gearbox. It may not have been marketed as a Chelsea, but maybe a Dana or Spicer. This box is not for heavy truck use, but maybe pick-ups or motorhomes. It weighs about 70 lbs. with a body of cast aluminum. I think it is probably about 25% overdriven. I do have a model number which is: 4800 074 133. Can anyone help with more specific information and maybe original manuals and set-up information?
Al | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | A pix would really help, may be an Al modern box, no parts available. Is it in a truck? Is it out on the floor? OpenPTO cover(if one) and look at innards. What does it say on tag?
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Dec 2007 Posts: 171 Shop Shark | | Shop Shark Joined: Dec 2007 Posts: 171 | Hello Ed,
I don't have posting pictures down for this forum but I can email directly to you if that may help to fully ID.
Al | | | | | Joined: Feb 2004 Posts: 29,836 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,836 | There are a lot of "Chelsea" brand PTO's on Ebay, mostly for recent-manufacture transmissions. It's possible they tried making a few direct/over boxes, didn't do their engineering just right, and had to do a recall.
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: Jul 2014 Posts: 17 'Bolter | | 'Bolter Joined: Jul 2014 Posts: 17 | Big Al
I installed a Gear Vender overdrive in my 1954 Chev 3800 and it works perfect.
Check out my pictures, in Tons of Fun, 3800 new posting photos. It show many pictures.
Richard | | |
|
|
Alan