Who has the older aluminum 3 speed OD transmission and how much power are you putting to it?

[Cop car wagon]

Dave6T4 is trying to talk some sense into you, but this is the same debate as trying to use an 8 3/4 behind a 440.
Full torque will make the od gear put too much force on the aluminum case and spread it, eventual failure. Iron case will slow down the failure. Using as a crutch for 3.91 or 4.10 on the highway just puts more heat in the ring and pinion, and failure. And vibration. Maybe for in town freeway, but I like to get out for thousands of miles.
8 3/4 behind a 440-4spd is fine until the pinion climbs the ring and brinels the pinion bearings. Usually on the first powershift.
Now the 3.09 standard, 1-1 output 4spd is a great trans for tall gearing road cruiser. Not much help for a 3.54 dana car though.
O.D. trans are just a synchro and tailshaft housing donor.

 

[dodgeboy440]

Dave6T4 is trying to talk some sense into you, but this is the same debate as trying to use an 8 3/4 behind a 440.
Full torque will make the od gear put too much force on the aluminum case and spread it, eventual failure. Iron case will slow down the failure. Using as a crutch for 3.91 or 4.10 on the highway just puts more heat in the ring and pinion, and failure. And vibration. Maybe for in town freeway, but I like to get out for thousands of miles.
8 3/4 behind a 440-4spd is fine until the pinion climbs the ring and brinels the pinion bearings. Usually on the first powershift.
Now the 3.09 standard, 1-1 output 4spd is a great trans for tall gearing road cruiser. Not much help for a 3.54 dana car though.
O.D. trans are just a synchro and tailshaft housing donor.

I’m learning every day …. U can’t fix stupid !

 

[Sinitro]

A friend of mine swapped an aluminium case O.D. transmission into his 1970 Challenger T/A 340 SixPack, for long drives to Mopar Nats, Chryslers at Carlisle, etc., from Ontario. However, for daily driving, he did not like the super-wide gear ratios behind the 340, and he eventually changed it back to its original close ratio 4-speed.

Keep in mind...
That the gear ratios of the OD transmission are almost the same as a 727 torqueflite...
A good choice for a street cruiser, but if U want more options than go with a 4 speed or Tremac..

Just my $0.02...

 

[Sedbld]

I put an iron case one out of an 84 truck behind a mild 383 (cam, intake, closed chamber small valve heads and steel head gaskets) in a 69 Roadrunner with 4:30 rear years ago and it was a total blast to drive to me. You couldn’t go 10 feet lol before you were hitting second but when your passing the guy next to you and you hit third and show him the taillights makes a smile that lasts a while !!! Only had the car about 2 years and miss it everyday !!

 

[Curiousyellow71]

With 3.23s at the dragstrip a 3 speed was nearly a second quicker then the same car with a 833 4 speed. It was in a 70 challenger with a grocery getter 360. 4 speed was 15.4, 3 speed was a 14.6. The three speeds 3.09 low got the car out of the hole better. Even though the 3 speed was quicker at the track it was not near as fun to drive as the normal 4 speed. 4 speed od drove like the 3 speed with big jumps.
When we ran the 4 speed od we flipped the 3-4 shift lever upside down to put 3rd gear back where it belongs. But it still wasn't enjoyable to shift w the big jump. We used to pick those 4 speed od up really cheap cause no one wanted them.

 

[Sinitro]

Note that today Passon Performance, actually tooled a new set of gears making an
18 spline 3 speed+OD transmission that can handle massive power..
Just my $0.02...

 

[j-c-c-62]

I suppose that is great news, but at what does this make any sense, vs just changing out the rear end ratio and/or adding a Passon Alum 833 case?

 

[Runcharger]

Without looking it up again the Passon unit has ratios the same as a 727 for first, second and third with a 2.66 first I believe. They drive really nice. The factory OD had 3.09 first then a big jump to second and a smaller jump to third which is direct, same as the Passon. We ran the Passon behind a 572 Hemi and it has ratios very well suited to the street and is trackable as well.