sb\bb Transmission question.

Technical Question and Answer - On topic to 71-74 Plymouth B-bodies only.

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mopardog
Satellite Sebring Plus (RP)
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My Cars: 1972 Road Runner 400 (project)
Location: River Valley, Arkansas

sb\bb Transmission question.

Post by mopardog » Mon Jun 03, 2013 10:14 am

Forgive me cause it's been a while.....when swapping a 727 from a small block to a big block....you need to change the bell housing right? Or will they interchange without a swap? Also, what's quickest way to determine between 904 and 727? My car was originally a bb 400 with 727, but previous owner stabbed a 318 in car when his son blew the 400. Wanting to get this car back right so any info would be greatly appreciated. Other than the power plant she is all original.
Long live "Ma Mopar"!!! 1972 Road Runner F7 Green, E68, build Feb 9, 1972, Deluxe trim. She's a little rough but she's mine all mine!!!!!

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road chicken
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Re: sb\bb Transmission question.

Post by road chicken » Mon Jun 03, 2013 1:15 pm

Whomever swapped in the small block also swapped in a 904A or 727A transmission behind it. Neither will bolt up to a Big Block.

They are different so you will have to swap to a 727B transmission. The bell housings are cast one piece with the transmission so, unlike a manual, you can't just swap the bellhousing.
4th generation B bodys- there is no substitute.
68 383, Street Demon 750, RPM top end,484/284/108 poo poo cam "-5 spd 4:10 SG, 4whl disk, Helwig Anti-Sway, Poly bushings,Firm Feel Box, HD Linkage, 1" t-bars, 7 leafs Springs

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mopardog
Satellite Sebring Plus (RP)
Posts: 81
Joined: Sun Jun 02, 2013 10:50 pm
My Cars: 1972 Road Runner 400 (project)
Location: River Valley, Arkansas

Re: sb\bb Transmission question.

Post by mopardog » Mon Jun 03, 2013 1:35 pm

thanks for the info roadchicken. Like I said it's been a while and kinda having to relearn everything. I will add that to list of parts to get this weekend.
Long live "Ma Mopar"!!! 1972 Road Runner F7 Green, E68, build Feb 9, 1972, Deluxe trim. She's a little rough but she's mine all mine!!!!!

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road chicken
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Re: sb\bb Transmission question.

Post by road chicken » Mon Jun 03, 2013 8:38 pm

No Problem, Wish I had a better answer for ya.
4th generation B bodys- there is no substitute.
68 383, Street Demon 750, RPM top end,484/284/108 poo poo cam "-5 spd 4:10 SG, 4whl disk, Helwig Anti-Sway, Poly bushings,Firm Feel Box, HD Linkage, 1" t-bars, 7 leafs Springs

gcoupe72
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My Cars: 1972 Road Runner originally equipped as lemon twist,400,4spd,air grabber,performance axle pkg.,bk. interior.
Location: North Carolina

Re: sb\bb Transmission question.

Post by gcoupe72 » Wed Jun 05, 2013 10:49 am

I don't know the source, but I believe there are "adapters" out there to put the LA trans on the B engine.
If you've got a lot invested in the small block trans., this would be another option.
I think people have also used these to put one of the overdrive automatics behind a big block.
Since, in production they didn't build a B engined O.D. trans.

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