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rear end ratios


Tom_Tams

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I'm trying to rebuild the differential on my "39 Special. The car is a Canadian built model with a standard rear end ratio of 4.44:1. Is this the same as the Flint built cars? I can get a NOS ring and pinion set from the Buick Farm but I don't know if it will fit.

Tom

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Guest imported_Thriller

By '39, the McLaughlin-Buicks differed generally only in badging (hub caps and the like). It will be a completely Buick driveline, so whatever they list at Bob's for your car should be fine.

Good luck. What part of BC are you in? My wife was born in Vancouver and grew up in the north...we visit friends in Cranbrook every few years if we can get out that way.

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Hi Derek,

Thanks for your reply, that's kind of what i thought, except for the wheels and lug bolt pattern everything seems to be pretty close. If the carrier and pinion are the same it will fit. The ratio given was 4.4:1 which is a difference of 1%, not a big deal.

I'm in Duncan on Vancouver Island just north of Victoria.

Tom

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Tom

You should look for the 3.9 gears that were optional in 1939 on the 40 series.Part number for the 4.44 gear set is 1394648 .The 3.9 part no. is 1394649.Ring part is 1303395[1303405 for 3.9]and pinion is 1310354[1310355]

Stan

Powell River

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  • 3 weeks later...

Stan, Thanks for the part numbers, I haven't been able to find a set of 3.9's although I would really like to, they're somewhat sought after and hard to find.

I got the gears from Buick Farm, the tooth ratio was 49:11 which doesn't match anything that I have listed in my manuals.

The part #'s are Pinion: 1323807, Ring : 1320946.

It would be interesting to find out what these gears actually fit.

Tom

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I don`t have these numbers in my parts list.But 3.9 is used on 1941-1942-40 1941-50 1942-60 1942-1949-70 1942-1949 40-50 1950-1952 40-50 1953 1953-46C-52-56C-59 C.T. 1953-40 1953-50 C.T. 1954-40-50-60 1955-40-50-70 C.T. 1956-40 C.T. But at lot of them with jobs.

Leif in Sweden.

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  • 5 months later...

Good Morning: I have several several complete rear ends with axels and other parts which are 3.9. Does anyone have an interest? They are from Buick small series cars from the 1950's, straight eights. Anyone interested? Cost would be $125 per unit. They must be picked up and not shipped. They are in the middle of Iowa about 20 miles north of I 80. I examined each ring and pinion and they appear to be in very good shape. Thanks, Patrick W. Brooks

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Guest 39convertible

Hi guys

i´m in the middle of a ground up restoration of my ´39 century convertible coupe 66c and i´ve did some digging in the ratio djungle and it´s not that easy to solve the ratio problem if you have a ´39.

The 1939 rear end is a one year only and nothing else would fit in without heavy machining on both the pinion and the banjo if you wanna have the original correct torque tube style.

the easyest thing to do is finding a complete 1939 3,9 diff.

i´m not saying its impossible but it´s not so easy.

There is always other ways to go: overdrive unit, automatic tranny with overdrive, modify a´40 and up complete rear end, but they all demand heavy modifications and are pretty expencive if you dont do it yourself.

personally i solv my problem for the convertible but if i do it again i´ll go for a 1956 rear end with 3,2:1 and try to machine it so it´ll fit and look like original as much as possible.

here is links to a few ideas:

http://www.transmissionadapters.com/index.htm

http://www.gearvendors.com/index.html

Janne

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Guest 39convertible

Yes

thats one of the Heavy machining issues i´ve talked about.

you have to make several changes to get the correct -39 appearance.

Janne

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