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Re: 700r4 Real axle ratio
#11
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Let the ride decide
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Ok, I will admit, I don't understand this "tall gear" talk, so I googled it, still don't understand it all, but this helped me, http://www.badasscars.com/index.cfm/p ... d=13/mode=prod/prd398.htm

Always interesting reading on this site.

Thanks

Posted on: 2015/4/1 12:57
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Re: 700r4 Real axle ratio
#12
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Owen_Dyneto
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People need to speak the same language when they chit-chat about rear axle ratios. When one speaks of a "higher rear axle ratio" if leaves open the question of whether they mean higher numerically, or of a higher gear ratio (meaning closer to 1:1 or direct drive), which are opposites. Numerically higher means, gear ratio-wise, a lower gear ratio meaning more engine revolutions per mile. A 4.69 ratio is numerically higher than a 4.07, but in the other context higher can mean a lower ratio because it is closer to direct drive, i.e. lower engine revs per mile. Just to complicate that, there is the expression of "taller" gears, which means lower numerically, i.e. possibly a higher top speed, assuming the power is there to take advantage of it.

Clear as mud?

Higher numerically: 4.69 is higher than 4.07
Higher non-numerically: 4.07 is higher than 4.69
Taller, 4.07 is taller than 4.69

As Jack and I were pointing out, the risk in going to "low" (meaning numerically lower) or "higher or taller" is engine lugging at lower engine revs which can do the dirty deed to main bearings. I'd rather have my engine rather effortlessly spinning without much effort at 2500 rpm than having it working its guts out and lugging at 1500 rpm or less.

Posted on: 2015/4/1 15:12
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Re: 700r4 Real axle ratio
#13
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PackardV8
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Correct reference to relative gear ratios is the use of "Long" vs "Short". Derived from the racing world meaning long race track or short race track gearing.
So a 2:1 ratio would be for a LONG track while a 4:1 would be for a short track.

But just exactly why does lugging an engine wear the main bearings??? Because oil pressure has dropped or what???? Just about any 'abuse' of an engine that will knock out the main bearings will ruin the rod bearings long before any main bearing symptoms would ever show up.

I just looked at the 56 Packard SM. The mains get oil BEFORE the rods.

Posted on: 2015/4/1 20:25
VAPOR LOCK demystified: See paragraph SEVEN of PMCC documentaion as listed in post #11 of the following thread:f
http://packardinfo.com/xoops/html/mod ... ewtopic.php?topic_id=7245
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Re: 700r4 Real axle ratio
#14
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Jack Vines
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Quote:
Just about any 'abuse' of an engine that will knock out the main bearings will ruin the rod bearings long before any main bearing symptoms would ever show up.


Not true in my experience or in the experience of the engine rebuilders with whom I work regularly. We and they see low RPM damage of main bearings when the rods are still in perfect condition.

Packard V8s are especially susceptible to main bearing wear. It's usual to see a Packard V8 with the mains turned .010" under and rods and bore still standard. If the engine has had hard use or been apart once, the cranks will often have to be .020" under and rods only .010" under.

jack vines

Posted on: 2015/4/1 21:45
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Re: 700r4 Real axle ratio
#15
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Mathew Rattray
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Update:

I pulled the diff out yesterday. I checked the ratio and it's a 3.54 ratio, ( 11 teeth on the pinion, 39 on the gear) unfortunately the hardening on the ring gear is worn, which would explain why it has been noisy. It looks like its time for a new gear set. I'll start the search for a new set, does anyone know of any sets available, I'd prefer a new set rather than a used set. I'me not quite up to speed with the Dana 44 or 60 models, do these gear sets fit the 55 model or only the 56 models.


Many thanks,
Mathew

Posted on: 2015/4/14 23:52
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Re: 700r4 Real axle ratio
#16
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BDeB
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Packard built their own differentials up to 1955 and only changed to Dana in 1956. Dana 44 for Clippers and Dana 53 for Packard models.
Not sure about availability of new which would have to be NOS, but any 3.54 ring & pinion set from 1954 or 1955 would work for your car and this was commonly used for the Senior models.

Posted on: 2015/4/15 0:45
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