7 1/4 to 8 1/4 upgrade with 2.45:1 gears

[3404speed]

The 7 1/4 was losing fast. Oil was drooling from both axle seals...so much so, that a puddle killed the grass next to the left rear tire. Ugh. I knew it had been coming for a while. The tell tale growl in the rear..was it the carrier bearings, pinion bearing or axle bearings? Well, likely the axle bearings judging from the leaking seals.

What to do? Quick look for new bearings for the 7 1/4 showed me that it would be close to a hundred bucks and I'd be into the job for a few hours. BAH!

There was only one thing left to do. Pull an 8 1/4 out of a duster I had laying in the driveway and upgrade the Dart. Couple hours doing that...oops had to hook on with the Ramcharger to get it out from under the shell...but it came out!

Next measure driveshafts and get one cut and balanced...after triple checking and gathering up a couple donor shafts...off to the fab shop to get that done...great guys at cook brothers truck in Elmira NY...$80 and a day later..shaft in hand(Pun somewhat intended) ;)
Now what?
Dang...be nice to get it on a lift to do the job...and Ramenth from F*BO had agreed to let me use the one in the garage he runs...sweet! Now I owe him one!

Friday...show up at noon...get it on the lift and start busting knuckles. 42 year old parts. Could be a real pain. I had oiled all the bolts, nuts, brake lines and anything else that might need to the be wrenched on.
it all came apart pretty well. Not bad for an old slant six dart with 80,000+ miles.
Back together, news brakes, wheel cylinders,and some new stainless steel lines left over from another project found new homes on the 8 1/4. Ready to roll.

Oh and those 255 60 15 tires really fill the wheel wells.
Nice! No noise from the rear. Smooth. No vibrations. And it stops. Big bolt pattern all around.


And the 2.45:1 rear? Cruises at 65 real easy. Hills just makes the trans kick down to second, so not much different than the 2.94's that came out. Haven't checked fuel mileage yet...need to get a set of 215 60 15 tires mounted and put the correct speedo gear in to fix the gearing/tire size differences. Should be better.
Now some pics.

 

[DusterKrazy]

Great!

People kept telling me that if I went with the 2.45's, it'd be a dog,weak, anemic..etc. I have a low gear 904 behind the 318. I still say that it can't be that terrible...
Great post and I will hopefully find out soon enough.

 

[Old Tired Rebel]

Subscribed

 

[ramenth]

The 7 1/4 was losing fast. Oil was drooling from both axle seals...so much so, that a puddle killed the grass next to the left rear tire. Ugh. I knew it had been coming for a while. The tell tale growl in the rear..was it the carrier bearings, pinion bearing or axle bearings? Well, likely the axle bearings judging from the leaking seals.

What to do? Quick look for new bearings for the 7 1/4 showed me that it would be close to a hundred bucks and I'd be into the job for a few hours. BAH!

There was only one thing left to do. Pull an 8 1/4 out of a duster I had laying in the driveway and upgrade the Dart. Couple hours doing that...oops had to hook on with the Ramcharger to get it out from under the shell...but it came out!

Next measure driveshafts and get one cut and balanced...after triple checking and gathering up a couple donor shafts...off to the fab shop to get that done...great guys at cook brothers truck in Elmira NY...$80 and a day later..shaft in hand(Pun somewhat intended) ;)
Now what?
Dang...be nice to get it on a lift to do the job...and Ramenth from F*BO had agreed to let me use the one in the garage he runs...sweet! Now I owe him one!

Friday...show up at noon...get it on the lift and start busting knuckles. 42 year old parts. Could be a real pain. I had oiled all the bolts, nuts, brake lines and anything else that might need to the be wrenched on.
it all came apart pretty well. Not bad for an old slant six dart with 80,000+ miles.
Back together, news brakes, wheel cylinders,and some new stainless steel lines left over from another project found new homes on the 8 1/4. Ready to roll.

Oh and those 255 60 15 tires really fill the wheel wells.
Nice! No noise from the rear. Smooth. No vibrations. And it stops. Big bolt pattern all around.


And the 2.45:1 rear? Cruises at 65 real easy. Hills just makes the trans kick down to second, so not much different than the 2.94's that came out. Haven't checked fuel mileage yet...need to get a set of 215 60 15 tires mounted and put the correct speedo gear in to fix the gearing/tire size differences. Should be better.
Now some pics.

John, when the hell did you sneak that pic of me?

Putting the rear up in the Dart was a blast. I have a customer from my restoration days who likes to stop by and shoot the s*** on his way home from physical rehab. He saw the 8.25 sitting there and asked what it was for. When I told him he said it was about time I got back to working on real cars.

John's car was also the topic of a running bet with my business partner's bro-in-law, Steve. I put front struts on Steve's '07 Ram Big Horn just a few days before. Four year old truck with 36,000 miles on it. I got my *** kicked for most of the day getting the lower control arm to strut bolt out of the driver's side. It's in a rubber bushing that had to be saved since it's DOI and was about two-three days out if I couldn't save it. Finally got the bolt out and saved the bushing, but it wasn't fun.

I told him that I bet John's '69 Dart - 43 years old on the model year - would come apart clean. It did. We had the old 7.25 out in something like half an hour, with the torch being needed only to heat the brake line flare nut going into the axle hose. Everything else was clean.

 

[ramenth]

Great!

People kept telling me that if I went with the 2.45's, it'd be a dog,weak, anemic..etc. I have a low gear 904 behind the 318. I still say that it can't be that terrible...
Great post and I will hopefully find out soon enough.

On paper, maybe. Real world? John's car is showing different. Especially where he lives isn't exactly flat ground. Even here in Elmira and Horseheads, where John works, the lay of the land isn't flat.

As a matter of fact, the kid's J-body came factory with a slant and 2.26's in the butt. To me, for that particular car, it was a good combo as a daily driver. His sperm donor used to drive the car to Syracuse and Rochester a lot. Great highway car, even with some of the bumps in the road on I-390 and I-81.

The best part about it was it was an absolute bear in the snow. Even on ice, with the open rear, the car wouldn't spin the tire. It didn't have the power and the gearing to do so. It just gripped and went.

 

[garageman1965]

I just put a 8 1/4 in place of the origional 7 1/4 in my 64 Dart GT I put in a 1979 8 1/4 out of a volarie service vehicle (cop car, taxi) and it to is a 2.45 posi unit behind a 226 slant 6 with a 904 14" tires, bigger bolt pattern, I did get shafted by the machine shop who shortened my drive shaft what I called he told 50, and when I dropped it off he said thats the old style it will be a little more, yeah 110 bucks more, live and learn next time I will ask how much more. :glasses7:

 

[3404speed]

After driving it for a couple weeks, it has not been a real problem at all going up hills. Initial acceleration is definitely not like a 340 4 speed with 3.55:1 gears, but it goes fine. Really nice cruising down the highway at 70 and the slanty buzzing along happily.

Scored a set of BFG 215 60 15 tires to match the size on the front. 15 x 6.5 Same size all around now, nice to be able to swap as needed.

Suspension work to follow, better shocks, sway bars, T bars maybe and a bit better rear spring. "Green Brick" on a much lower budget. Highway cruiser.

 

[DusterKrazy]

Nice!

Glad to hear you are enjoying it. My friend has a Diplomat (which is heavy) with a 318. It has the 2.24 gear in the back and it's not as weak as people would think at all. Very nice on the highway. The 318 has dual exhaust and an Edelbrock 500cfm 4 barrel...well the catalytic converter is gone to..lol. Anyways, in a lighter car ('71 Scamp) it should be a nice package.

What driveshaft would be right for this application? 318-->904-->8 1/4. I did a swap for the Scamp by trading a '69 Barracuda. Didn't realize the wheelbase was different. Oh well, live and learn.