3speed with overdrive stories - The 1947 - Present Chevrolet & GMC Truck Message Board Network

davidh · 10-23-2005, 02:43 PM

okay, I'd like to hear of 3speed overdrive stories. How well do they work? How much rpm drop? When do you pull out the t-handle? I'm very curious to one of these.

I might want to add one to my 67' so also if you got a complete set up let me know.

**pjmoreland** · 10-23-2005, 02:49 PM

I had that setup behind an inline 6 250 motor in my old '67. I got 21 MPG on the highway. I'm not sure how the electric shift solenoid was hooked up from the factory, but mine was wired to a switch on the dash. I'd push the T handle in to make the overdrive unit freewheel like a bicycle. Then I'd throw the switch, lift my foot off the accelerator, and as the RPM of the motor slowed down, the overdrive unit would kick in. It was kind of tedious to engage the overdrive unit this way. I'm assuming that the factory setup must have been a little less idiot-proof.

davidh · 10-23-2005, 04:01 PM

I'd like to put one behind a V8. Now I know obviously I can't be pulling a 5th wheel stock trailer with this but I'd like a little extra down the highway.

llegos · 10-23-2005, 04:18 PM

i am also interested in one of these, but i dont think they bolt to the NP435GA

Longhorn Man · 10-23-2005, 08:52 PM

just a note, they are hard to find, imposable to get parts for, and very weak. A T5 is probably stronger, and the T5 is as strong as a wet paper bag.

**pjmoreland** · 10-23-2005, 09:01 PM

I suppose that's why they came with the inline 6 motors. I got power-hungry and traded mine for a TH350 and a V8.

**PICKMUP** · 10-23-2005, 09:25 PM

They came behind v8s also. There was a loaded 67 CST here with 327/3spd/OD. That was a great highway cruiser. I never got to check the rear ratio.
I am working on a 67 GMC 250/6 with complete original OD. It is running a 3:92 rear ratio in a dana 44. I haven't got to the OD yet, but it is not engaging. LivRat was down and gave me some ideas on items to check in the electronics. He also has some tips on putting this OD unit behind a 4spd.
I sold a complete unit on here a couple years ago. I wonder if it was ever installed and working?

Longhorn Man · 10-23-2005, 10:46 PM

the over drive was supposed to be only installed with a 4.10 gear, and I had thoguht behind 307 and smaller engines...I don't have my papers here, i left them at work.

**pjmoreland** · 10-23-2005, 10:54 PM

My '67 had 4:11 gears originally.

10-23-2005, 02:43 PM	#1
davidh Senior Member Join Date: Feb 2004 Location: Ponca city now kingfisher Oklahoma Posts: 1,221	3speed with overdrive stories okay, I'd like to hear of 3speed overdrive stories. How well do they work? How much rpm drop? When do you pull out the t-handle? I'm very curious to one of these. I might want to add one to my 67' so also if you got a complete set up let me know.

10-23-2005, 02:49 PM	#2
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,406	Re: 3speed with overdrive stories I had that setup behind an inline 6 250 motor in my old '67. I got 21 MPG on the highway. I'm not sure how the electric shift solenoid was hooked up from the factory, but mine was wired to a switch on the dash. I'd push the T handle in to make the overdrive unit freewheel like a bicycle. Then I'd throw the switch, lift my foot off the accelerator, and as the RPM of the motor slowed down, the overdrive unit would kick in. It was kind of tedious to engage the overdrive unit this way. I'm assuming that the factory setup must have been a little less idiot-proof.

10-23-2005, 04:01 PM	#3
davidh Senior Member Join Date: Feb 2004 Location: Ponca city now kingfisher Oklahoma Posts: 1,221	Re: 3speed with overdrive stories I'd like to put one behind a V8. Now I know obviously I can't be pulling a 5th wheel stock trailer with this but I'd like a little extra down the highway.

10-23-2005, 04:18 PM	#4
llegos Registered User Join Date: Aug 2005 Location: pleasanton, CA Posts: 570	Re: 3speed with overdrive stories i am also interested in one of these, but i dont think they bolt to the NP435GA __________________ -Steve

10-23-2005, 08:52 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 3speed with overdrive stories just a note, they are hard to find, imposable to get parts for, and very weak. A T5 is probably stronger, and the T5 is as strong as a wet paper bag.

10-23-2005, 09:01 PM	#6
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,406	Re: 3speed with overdrive stories I suppose that's why they came with the inline 6 motors. I got power-hungry and traded mine for a TH350 and a V8.

10-23-2005, 09:25 PM	#7
PICKMUP "Trucks with Class" Join Date: Jul 2000 Location: OLYMPIA, WA, USA Posts: 8,125	Re: 3speed with overdrive stories They came behind v8s also. There was a loaded 67 CST here with 327/3spd/OD. That was a great highway cruiser. I never got to check the rear ratio. I am working on a 67 GMC 250/6 with complete original OD. It is running a 3:92 rear ratio in a dana 44. I haven't got to the OD yet, but it is not engaging. LivRat was down and gave me some ideas on items to check in the electronics. He also has some tips on putting this OD unit behind a 4spd. I sold a complete unit on here a couple years ago. I wonder if it was ever installed and working? Last edited by PICKMUP; 10-23-2005 at 09:26 PM.

10-23-2005, 10:46 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 3speed with overdrive stories the over drive was supposed to be only installed with a 4.10 gear, and I had thoguht behind 307 and smaller engines...I don't have my papers here, i left them at work.

10-23-2005, 10:54 PM	#9
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,406	Re: 3speed with overdrive stories My '67 had 4:11 gears originally.



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