Gearing Up To Change Gears

[55 Fargo]

Decided to take the plunge and change the hoghead in my 4.30 diff, with a 3.54 hoghead from my partscar.

Today I tried to pull away from a dead stop in 2nd gear, with my 4.30 rearend, it pulls way no problem.

With the taller 3.54 gears, it should have no problem taking off in 1st gear, the drive ratio in 1st gear is something like 9.15 to 1, with a 3.90 diff it is 10.05 to 1, so there is not that much difference.

I will pull the pumpkin out of my parts car this week, I will then have it inspected, after that I will pull the axles out of the recipeint, pull its hoghead, and hopefully everything will match up.

If they are different, not sure what I will do at that point, but hopefully they match up.

This should drop my highway rpms a great deal, looking forward to this.....................Fred

[55 Fargo]

I know all of the diff questions are probably not making me popular, but I want to get all of my ducks ina row before thye big switch.

The thing I am trying to figure out is this, the diff in the car is a 4.30, it has 11 inch brakes, so it's not from the big Chrysler, it had 12 inch brakes.

This diff has an anti-sway bar, covered 9 leaf springs, and the shock protector plate is huge.I had to get slightly longer than stock shocks to fit.

I am not sure if truck rear ends, had the anti-swaybar,covered leaf springs or not.

My parts car is a 47 Chrysler, with a 3.54 diff, it has the anti-swaybar, covered leaf springs.

I am trying to figure out if the 4.30 diff is a 40s, or 50s rearend, as the swap of hogheads, might be different using a 40s hoghead with a 50s rearend, in particular the axle splines.

I think most trucks came with 4.10 gears, and the big Chryslers and Big Dodges, may have had 4.30 diffs with standard transmissions..................................Fred

[Young Ed]

Fred

I've seen the 4.30 listed as an option for cars and trucks. You shouldn't have issues with this swap. On my 48 the diff I swapped had the wrong axle spline count so my existing side gears were reused in the new diff. Just make sure you check that before you find out like I did-when your axles won't go back in!

[55 Fargo]

Thanx Ed, Iam hoping it will bolt right in, and no problems with the axle splines either, I plan to pull the hoghead from the parts car this week, will have a good look then Fred

[randroid]

Fred,

Just a thought for when you have the axles out, there's a grease point on the end of the housings for lubing the rear seals that might warrant your attention and this would be the easiest time to address it. It isn't a zerk (because that would allow too much pressure) but rather a bolt on the bottom that's removed so more grease can be crammed in. My understanding is that traditionally these fittings are either ignored or refilled without being cleaned, thereby rendering them all but useless.

I'll do mine before I put my '48 P-15 back on the road next Spring but as yet I have no hands-on experience with them. Anybody else in here ever clean theirs?

-Randy

[55 Fargo]

Thanx randy, I have been wondering what to do with them as a matter of fact.

Also, when I pull the drums, do I need to take my brakes off the backing plates, to remove the axles. Would like to disturb my brakes the least, as they are new and working...........Fred

[Young Ed]

On a few cars that I was hauling out of junkyards I have pulled those plugs, put a fitting in there and pumped the bearings with some fresh grease, then replaced the plug. 2-3 times now I've towed vehicles that haven't been moved for decades with the rear wheels on the ground and the front on a dolly.

[Merle Coggins]

On a few cars that I was hauling out of junkyards I have pulled those plugs, put a fitting in there and pumped the bearings with some fresh grease, then replaced the plug. 2-3 times now I've towed vehicles that haven't been moved for decades with the rear wheels on the ground and the front on a dolly.

That's what is stated in my truck manual for regular maintenance.

Every 20,000 miles, remove the plug, inject 1/2 oz. of grease with a low pressure gun, reinstall plug.

Merle

[55 Fargo]

The diffs from early 40 s, to say, what 1953, you can switch hogheads directly. What is different about the newer years 1953 forward, can you tell from the outside housing. The 4.30 diff on my Chrashler is of unknown origin, so don't have a clue what it is from or the year. It does have two filler holes on it, one on the hoghead, one on the diff housing.............Fred

[55 Fargo]

Just come in, got the parts car blocked up, wheels off, and drums off. The brake shoes had lots of lining on them, drums are pretty good too, but they need a little machining.

Before I took the wheels/drums off, I spun the rear wheels, no noises from the diff, no grinding, but lots of play.

How much free play, is considered okay. If there is too much play, can this be corrected from a shop.

Tomorrow, plan to pull axles, and remove the hoghead, then will have a good look at what I got, at least it's a 3.54.............Fred

[55 Fargo]

Pulled Pumpkin, not so happy to anounce the diff is a 3.73, and not the 3.54 I thought it was, oh well, better than a 4.30. Pulled axles out with bare hands and no puller, after the drums were off, the rest was a cake walk, so to speak. Will post pics and more details later.Fred

[Young Ed]

Where did you get the 3.73 from? Off the carrier or the ring gear itself? If you rotate the ring gear it should have a ratio stamped on it.

[55 Fargo]

It is on both the carrier and it is stamped on the ring gear. Plus there is a lube filler on both the carrier and the back of the diff housing. That would indicate it was switched, the old style 3.54, has it's filler on the back of the diff housing, and others have it on the hoghead, is this correct. Just glad to have it out, it appears to be in good shape, no metal filings, wear doesn't look too bad, spins freely. The axles and bearing were also in good condition.................Fred

[Young Ed]

Fred you got me on that one. I've seen many that had 2 plugs like yours. Not sure what is up with that.

[55 Fargo]

Here is a pic of the diff and my worksight with the axles, it is a beautiful fall day here about 60 degrees, nice working weather,

You can see the 3.73 stamp on the gear, there was about 1.5 pints of gear lube, not enough but enough to keep it lubed a bit, the bearings and axles seem in good condition. There were no metal filings in the diff housing or the lube...Fred