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View Full Version : Rear Axle: Questions regarding OD retrofit



MrBulldops
10-17-2017, 10:46 PM
I've got a '60 Lark, 6-cylinder with a 3-speed. I've been giving some thought to swapping the transmission with a 3-speed overdrive unit and want to get anyone's experience with rear end gearing. I've currently got a 3.73.

Acceleration is...acceptable.

But, I didn't buy this car to go zooming, I bought it to cruise. My concern is that the OD gearbox ratios might slow my car to a crawl. I'd like to get 65 or 70(ish) MPH at a reasonable engine speed. Off the line isn't all that important aside from that I'd prefer not to get run over leaving from stop lights. Already people get pretty impatient (AZ drivers are always in a hurry).

Where I live isn't particularly hilly, but there are some places up north I'd like to drive sometime but there's about a 3000ft difference in altitude. I haven't tried to drive up there yet because some of the hills around town will already increase the engine temp a whole pip on the gauge.

So, anyone have this setup or another recommendation--other than "V8 swap"--I should consider? Just trying to get ideas before I dive to much into this.

fpstude
10-18-2017, 01:22 AM
Our '60 Lark is a 3-speed with overdrive. It has a six-cylinder engine. I believe it experienced a pretty rough life before it became ours. It had a 3.08 rear end. As you can imagine, it was very sluggish. I purchased a rear end with a 4.27 ratio. The difference was like night and day. It travels quite well at 70 mph. Hope this helps with your thought process.

StudeRich
10-18-2017, 02:21 AM
The 3.73 Ratio will be perfect for the planned use you describe. A 4.10 Ratio Model 27 Axle would also work well, but since you already have a 3.73 you should be good to go. You will be pulling those Hills in direct 3rd. but you will be better than good on the flat, and OK at stoplights, just not as Fast as a New $25,000.00 Honda!

I do not suggest trying to "convert" the actual Manual Trans itself to an Overdrive one.
Just install a T-96 that HAS Overdrive, as too many Parts including the Mainshaft and Case are different.
Your word: "Swap" is exactly right. :)

gordr
10-18-2017, 02:31 AM
Mr. Bulldops, if you are in the Phoenix area, or, more specifically, the East Valley, come over for a visit. I have a '60 Lark here in Apache Junction, with an OHV six in it. Almost roadworthy. And I plan to do the same exact thing, pop in an overdrive transmission. It has the straigth three-speed now. Send me a Private Message via this site, if you want my contact information.

Mrs K Corbin
10-18-2017, 06:34 AM
get the driveshaft with it, or just buy a whole parts car for the setup, as there are quite a few parts to go with it.

PackardV8
10-18-2017, 09:20 AM
get the driveshaft with it, or just buy a whole parts car for the setup, as there are quite a few parts to go with it.

Definitely do not buy it one piece at a time. Find a Lark with OD and get the in-out cable and bracket, kickdown switch and throttle linkage, wiring harness and driveshaft. Make sure the transmission has the governor and solenoid.

jack vines