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| | | | Joined: Dec 2009 Posts: 66 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2009 Posts: 66 | Hello All,
I need some opinions of the best or a good rear end gearing. This is what I am running.
1. 350/290hp
2. 700r4 trans.
3. 15" rims P225/75R15
4. existing transaxle 10 bolt, 8.5" 2.41/1 ratio.
I want to keep the existing housing and change the gears to 3.42/1 limlted slip.
All oipinions are welcome.
Thank you,
Al
| | | | | Joined: Mar 2010 Posts: 843 Shop Shark | | Shop Shark Joined: Mar 2010 Posts: 843 | Al, I tried to run a 3.40 rear gear ratio in my '32 Ford roadster with an engine similar to yours, slighhtly taller tires and a 2004R trans. In overdrive at legal freeway speeds the engine was lugging way below its comfortable operating range. Changing to a 3.80 gear solved the problem and it pulls the OD gear easily on the freeway or open road.
For purposes of comparison my engine is a 350 SBC, Edelbrock 70cc heads yielding 9:1 compression, Performer manifold and optimized 600 CFM carb, Crane camshaft with duration at .050 of 218* and 230*, tires are 285/70-15 and a tight converter.
I hope this helps.
Ray
| | | | | Joined: Dec 2009 Posts: 66 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2009 Posts: 66 | Ray, Thank you for the info. Looks like I need to rethink these ratios.
Al | | | | | Joined: Dec 2001 Posts: 14,522 Moderator: Welcome Centre, Southern Bolters, Legion Hall | | Moderator: Welcome Centre, Southern Bolters, Legion Hall Joined: Dec 2001 Posts: 14,522 | Al, I don't know if I told you what I'm running but the 1980 Malibu rearend I have does a great job with my 350 (400hp) and 700R4 tranny. If I remember reading it correctly the rear is a 3.73 Regardless it makes it move when I want to move but it also runs very very nice on the interstate. man, it crusise | | | | | Joined: Apr 2005 Posts: 2,832 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 2,832 | I think the 700R4 has about a 30% overdrive so take 0.7 times whatever rear you choose to get a final drive ratio. The 3.42 gives a 2.39 final which may be a little shallow for bucking head winds or in hills. The standard factory OD rear for years was a 4.11 which gave a 2.88 final. I think modern engines can handle a bit less gear but one reaches a point that using a bunch of throttle to maintain speed ruins the shallow gear economy.
Evan
| | | | | Joined: Dec 2009 Posts: 66 Wrench Fetcher | | Wrench Fetcher Joined: Dec 2009 Posts: 66 | Thank you all for the info. I've decided to take all advice and will install 3.73 gears. Pulled the rear out yesterday and delivered to the rebuilder. Called him this AM and informed him of my final gear selection (3.73).
Again, thank you all for info.
Al | | |
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