Third members question

[dropshot1]

I have 1970 swinger 340 with an open 741 with 3:23 gears, I would like to eventually put in 3:91's with a sure grip.can I purchase a 489 or 742 pumpkin, and bolt in and go with no problems, will they all work with my u joints and factory drives haft with no differences. Thanks for any input

 

[dukeboy440]

I have 1970 swinger 340 with an open 741 with 3:23 gears, I would like to eventually put in 3:91's with a sure grip.can I purchase a 489 or 742 pumpkin, and bolt in and go with no problems, will they all work with my u joints and factory drives haft with no differences. Thanks for any input

There are differences in the yokes, thus the the u joint sizes . However, there's two types of yokes for the 489, a large and small, the small is the one you'll need to connect the driveshaft from the 741

 

[65-440]

I thought all H- code swingers had 489 case sure grips?

 

[dukeboy440]

I thought all H- code swingers had 489 case sure grips?

When it came to third members, I've yet to narrow down a 100 percent certain as to what came with what. I've seen 741s behind big block cars and I've see 489s behind 318s.

 

[Locomotion]

There are fine spline and course spline yokes, so you'll have to use a yoke that not only fits the spines of your new ring & pinion, but also the driveshaft u-joint. The yokes will interchange between housings.

You could swap the old yoke into the new center section if the splines and u-joint size match. But whoever is setting up the new gears will need both centers to set it up. However, keeping the whole old 3.23 center as a spare could come in handy if you ever need the gearing for a long trip.

 

[oldkimmer]

Fine spline started for the 71 or 72 model year

 

[dropshot1]

So I think then I need the small yoke with a course spline, sound correct? Thanks guys for the help

 

[oldkimmer]

It should be, BUT u never know as it's a dam near 50 year old car. Kim

 

[Daves69]

So I think then I need the small yoke with a course spline, sound correct?

Or a possibility.................
PLYMOUTH DODGE MOPAR 7260 X 7290 CONVERSION COMBINATION UNIVERSAL JOINT U JOINT | eBay

 

[Locomotion]

Wait until you get the new center section before settling on a yoke. The spline count will depend on the ring & pinion. There are new ring and pinions that are manufactured with either spline count. A used center section can have either as well. At this point, what the car came with is irrelevant.