Mail Truck Transmissions

Adger Smith · 11-17-2023, 03:28 PM

Who was the Guy/Company that modified the 904 trans with the SBC bellhousing bolt pattern?
I have had 2 of these for a while that I'm considering building...
They came out of the Postal mail trucks with the Chevy 4 cylinder engine.

Alan Roehrich · 11-17-2023, 03:31 PM

Modified in what way?

Adger Smith · 11-18-2023, 09:16 AM

Valve body with brake and to fit PG converters

SSDiv6 · 11-18-2023, 12:13 PM

Quote:

Originally Posted by Adger Smith

Valve body with brake and to fit PG converters

Adger,
You should reach out to Pro-Trans in Texas or Joel's On Joy in Michigan.
If I am correct, those transmissions have the guts of a 904 with a GM bellhousing.

340Cuda · 11-18-2023, 01:48 PM

Quote:

Originally Posted by SSDiv6

Adger,
You should reach out to Pro-Trans in Texas or Joel's On Joy in Michigan.
If I am correct, those transmissions have the guts of a 904 with a GM bellhousing.

Adger,
I always thought they were just 904s and I am sure Pro-Trans would know all about them.
Bill

FED 387 · 11-18-2023, 09:38 PM

We tried to use those transmissions on a GM 4 cylinder in COMP F/ed---the problems we ran into were starter pocket location-- then making a flexplate to adapt(both crankshaft and t. convertor bolt patterns)and the odd ball torque convertor they used it was kind of a quasi GM/Mopar set up and then the input shaft is MOPAR and the convertor we tried to use was PG spline plus the tangs for the pump on the convertor were again MOPAR and NOT the PG style another modification that had to be made--also the output shafts are 23 spline count versus PG /350 of 27 spline so you need a different slip yoke-after a lot of trying and fabricating we finally got it to work--next problem was gear ratios if you have the "LATE " trans ---used from 1982-3 forward you most likely have a 2:74/1:54/1:00 set up and if you have an "EARLY" trans before 1982 it "could/should be" a 2:45/1:45/1:00 ----a "supposedly sure fire way" to tell if it is the HIGH gear is if it has a 3 or 4 plate REAR clutch pak its a 275--- but I'm not sure of that better talk to a knowledgeable trans guy---we tried it and both first gears were too severe for our 1100 pound dragster---- might work in a heavier car or in a unique street rod etc.---as with all things JEEP they were struggling at that time and sourced parts from any/everybody to put vehicles together--------- FED 387

11-17-2023, 03:28 PM	#1
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Mail Truck Transmissions Who was the Guy/Company that modified the 904 trans with the SBC bellhousing bolt pattern? I have had 2 of these for a while that I'm considering building... They came out of the Postal mail trucks with the Chevy 4 cylinder engine. __________________ Adger Smith (Former SS)

11-17-2023, 03:31 PM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,125 Likes: 1,583 Liked 1,880 Times in 422 Posts	Re: Mail Truck Transmissions Modified in what way? __________________ Alan Roehrich 212A G/S

11-18-2023, 09:16 AM	#3
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Mail Truck Transmissions Valve body with brake and to fit PG converters __________________ Adger Smith (Former SS)

11-18-2023, 09:38 PM	#6
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,423 Likes: 539 Liked 333 Times in 180 Posts	Re: Mail Truck Transmissions We tried to use those transmissions on a GM 4 cylinder in COMP F/ed---the problems we ran into were starter pocket location-- then making a flexplate to adapt(both crankshaft and t. convertor bolt patterns)and the odd ball torque convertor they used it was kind of a quasi GM/Mopar set up and then the input shaft is MOPAR and the convertor we tried to use was PG spline plus the tangs for the pump on the convertor were again MOPAR and NOT the PG style another modification that had to be made--also the output shafts are 23 spline count versus PG /350 of 27 spline so you need a different slip yoke-after a lot of trying and fabricating we finally got it to work--next problem was gear ratios if you have the "LATE " trans ---used from 1982-3 forward you most likely have a 2:74/1:54/1:00 set up and if you have an "EARLY" trans before 1982 it "could/should be" a 2:45/1:45/1:00 ----a "supposedly sure fire way" to tell if it is the HIGH gear is if it has a 3 or 4 plate REAR clutch pak its a 275--- but I'm not sure of that better talk to a knowledgeable trans guy---we tried it and both first gears were too severe for our 1100 pound dragster---- might work in a heavier car or in a unique street rod etc.---as with all things JEEP they were struggling at that time and sourced parts from any/everybody to put vehicles together--------- FED 387 Last edited by FED 387; 11-18-2023 at 09:46 PM. Reason: spelling