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Lincoln rear end help/suggestions odd duck

3K views 7 replies 7 participants last post by  mustangman.jg 
#1 ·
Hello all, I am hoping you can help me out again (as you always do) with some odd duck lincoln questions, and general newbishness to rear ends.

What I have is a 1969 linc conti 4d, 460/C6 with a 2.80 rear open diff. factory option for that year is a 3.00, LSD also optional. but i dont have those.

this car is 5200lbs+, im sorry i dont know the factory stall speed off hand. it cruises well only pulls 2100ish at 60mph. but it doesnt accelerate off the line well at all. i have used some online calculators to see how much rpm would be affect with various ratios (tires are 235/75/15s).

what would you guys suggest is a ratio that would increase the fun factor and still be livable for driving corss country interstate? also considering switching to a LSD if i could.

now i think i have a 9 3/8 rear on this, not lincoln specifc just pre 70s ford stuff right? i have been told that entire carrier housing and assebly from a 9in, with 31spline axles will swap over. do you know anything about this? possible good donor cars?

is there no parts for my axel as is? when i look online i havent seen a 9 3/8 on the usual sites. A member of my lincoln forum bought 9in gears and they didnt fit so we know that wont work.

to sum up, what can i use to make this work, and what target ratio should I be shooting for?

I hope I have given you enough information, and thanks for any and all help!

-Adam
 
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#3 · (Edited)
Regarding the 9-3/8" rear you are not going to find any new ring and pinions for it. Used or NOS is it. They did make a 3.50 ratio, but may take some looking to find a good set.

A 9" will bolt into the axle housing and provided it is a 31 spline unit you may or may not be able to reuse your axles. The side gear offset is different between a 9" and 9-3/8". Some have done the swap and re-used the original axle with no issue, some have had failure. You need to make sure you have the correct spline engagement. The pinion yoke should swap ok.

That said the 9-3/8" carrier is a HD piece - nodular iron case, 4 spider gears, big pinion support and carrier bearings, and of course a larger ring and pinion set. If you build a 9" I'd figure on a nodular iron case, daytona pinion support, 4 spider gears, etc...
 
#4 ·
The 9 inch carrier assembly is interchangeable. I put a Detroit Locker in mine.
If you want a used set of gears look in a 1978 or so F150. That's what mine came out of. It was a posi to boot.
 
#7 · (Edited)
Same gearing scenario with my 76 Mk.4 (p.10 of photo albums) Started with engine mods. Desmog, 030, mild cam, mild head work, stock int.& carb, all new 2 1/2 pipes & mufflers, standard rebuild of C6. Much improved performance but only when manually working the auto gears. After lengthy research, seems like 3:25s' are best answer for my 5483lb car. 3:50s' strong contender but increase in rpm becomes a healthy concern and especially so if you're going to mash it. The stock springs in your heads are a bit too soft for high revs. At least, mine were and I bent a pushrod.
 
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