Shooting the breeze. What’s the 1/4 mile time of a 340 challenger?

[kawahonda]

Not sure. Dr. Diff requires you to select either or before ordering a chunk.

[kawahonda]

Pretty sure I have the factory OEM tapered wheel bearings (not the green ones). But yes, I am required to select  7290 U-Bolt or 1350 U-Bolt for the pinion yoke option.

[RUNCHARGER]

It should be a 7290 if still factory. I always measure them to be sure.

[kawahonda]

How would I go about measuring? Very highly sure it is still factory....this car hasn't been touched much.

[1 Wild R/T]

It won't have a 1350.... It might have a 7290.... But some 340's had 7260's...  Back around 82 my buddy bought a pair of Lakewood high nickel content 7290's for his 4spd T/A.... Only to find it had 7260's.... So I got a great deal on a pair of high quality U joints....

And as far as telling which is which....

[GY3R/T]

   You are choosing the size of the pinion yoke. I believe Dr. Diff uses a U-bolt to secure 7260 or 7290 U-joint to yoke. Instead of straps and bolts that screw into the yoke, It's a U-bolt that slides thru the yoke & nuts are screwed onto The U-bolt from the backside of yoke.  Not OEM, but stronger. I would order the large 7290 even if i had 7260 drive line. They make U-joints that are 7260 x 7290.   

[kawahonda]

Thanks guys. So regardless, the 7290 is what I should order.

[kawahonda]

Welp, I'm pretty much ready to order a chunk! I've decided on a 3.73. If I get tired of it, then I'll just add 3.55 to the center section.

If I'm going to be replacing the chunk, there's a few other things I should do while I'm at it.

1) Repack bearings. I suppose any grease will do?

2) Should I replace the axle seals?

3) Do I need to order a gasket for the center section? What RTV to use?

I think that's about it.

[Chryco Psycho]

I use wheel brg grease in the brgs , I like Castrol but any good quality grease is fine
I would change the inner seals But you need a correct driver otherwise you can destroy the seals trying to install them , if you do not have an installer & it is not leaking it may be better to leave them alone
I have installed both ways , with or without a gasket , I use ultra grey silicone with high oil resistance
Make sure you set the end play correctly too , I seat the axles with a large hammer driving the brgs away from the adjuster side & tighten the adjuster , you want about .010 end play .

[RUNCHARGER]

And of course you know to be very careful pulling the axle splines past those seals so you don't knick them.

[kawahonda]

Thanks guys. It should arrive by Wednesday.

When I pull the axles, do I want to simply just add more grease to the bearings? It’s my understanding that they are pretty shielded.

What’s more stock? Using a gasket or not? Even with a gasket, some RTV on both sides a good idea?

I won’t touch the seals.

I’ll measure my yoke when I pull my third member. Assuming I can muscle it out without another hand...

The OD of my tires is 26.1. Obviously when it’s mounted it’s less. Assuming I’ll need a “blue” 38 speedo gear?

[kawahonda]

Hi all,

Everything is going well. Got everything cleaned. Ready to put new pumpkin in soon.

I've decided to not replace the seals. It's an easy replacement later if they start to leak. same with axle retainer gakets, decided to let those be as well.

I inspected the u-joints. I see some scoring. I believe that they should be replaced.

I measured my U-joint/yoke, and yes, I have the 7290 style.

My question is are both U-joints the same (front and rear of shaft)?

I believe that this is a direct replacement for my rear u-joint:
https://www.oreillyauto.com/detail/b/masterpro-u-joint-4353/cv-driveshaft-axle-16804/combination-u-joint-12825/0c05bd50d9eb/masterpro-combination-universal-joint/355/4507190/1970/dodge/challenger?q=U+joints&pos=0

Is the front one the same?

[7212Mopar]

That does not appear to be a direct replacement u joints as dimensions of both trunions are not the same. More like a conversion u joint. 7290 will use inside clips on all four cups. You can go to Denny driveshaft website to check the info.

I would just pick up two non-geasible Spicer 7290 u joints. A lot of online stores and Napa auto carry them. If your driveshaft is stock with 7290 u joints, front and back are the same.your driveshaft should already be off the car so easy to check.

[kawahonda]

Cool. I bet these are what I need:

https://www.dennysdriveshaft.com/p463_dana_spicer_5_811x_universal_joint_non_greaseable_7290_serie.html

[7212Mopar]

 

Lots of Youtube videos on replacing u joints, make sure everything are seated correctly, no binding and move freely.