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By Eric - 7 Years Ago
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I have a 1956 ford fairlane differential with 3.90 ratio. Would like to go to 2.90 or 3.0 What would be the easiest option? Is there something else i can bolt right up to same housing? It has 17 spline axle shafts. Thanks
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By Dobie - 7 Years Ago
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The easiest option would be to find a good diff from a mid 50s Ford that had an automatic in front of it. Those are around 3.30:1 and bolt in. A good modern diff would be the 8" from a Ranger or Exploder however the pumpkin is offset to the left so you'd need to get another right hand axle & tube to center it. Those come in a variety of ratios and custom ring & pinion sets are available if none of the stock ratios suit your needs.
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By Joe-JDC - 7 Years Ago
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Dobie (12/17/2017)
The easiest option would be to find a good diff from a mid 50s Ford that had an automatic in front of it. Those are around 3.30:1 and bolt in. A good modern diff would be the 8" from a Ranger or Exploder however the pumpkin is offset to the left so you'd need to get another right hand axle & tube to center it. Those come in a variety of ratios and custom ring & pinion sets are available if none of the stock ratios suit your needs.
The Ranger and Explorer differentials are 8.8", not 8". They are completely different, the 8" is a removable chunk like the Ford 9", but the 8.8" has a rear cover, and the gears must be set up in the housing. Joe-JDC
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By MoonShadow - 7 Years Ago
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Eric, where are you located? It helps to put city and state in your tag line. I have a couple spare pumpkins for the 56 Ford stock rear end. I can check the gear ratios if you like and would be willing to sell at least one. Shipping may be a problem depending on where you live.
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By Eric - 7 Years Ago
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Moonshadow,
Thankyou for the response. I live in Fond Du Lac WI. I would be interested in what you have if it is in the 2.90 to 3.00 or so ratio. Photos would be great also to confirm it is correct. I would really only need the ring and pinion I believe. Let me know . Thankyou,
Eric
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By paul2748 - 7 Years Ago
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. There is nothing that is a bolt in in the ratios you are looking for. The nearest would be an automatic rear which is around 3.30. Other than that, an early (57-58) rear would bolt in but you would have to find a set of gears in the ratios you are looking for. Usually, they are available.
Eric (12/17/2017)
I have a 1956 ford fairlane differential with 3.90 ratio. Would like to go to 2.90 or 3.0 What would be the easiest option? Is there something else i can bolt right up to same housing? It has 17 spline axle shafts. Thanks
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By MoonShadow - 7 Years Ago
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They are take outs from a 56 probably 3:30's. I replaced mine with a 3:80 posi unit. Found the Detroit Gear original 56 Posi unit on EBAY several years ago. Will check tomorrow.
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By Lou - 7 Years Ago
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56 auto rear gear is 3.22, all others that bolt in (49\/55) are 3.30. If you use a 49/55 you have to use 49/55 axles.
What engine and trans are you running.?
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By Dave V - 7 Years Ago
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Lou is correct. 56 automatics used a 3:22 gear
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By Eric - 7 Years Ago
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Lou
I am running a 351c with fmx 3 spd auto. Turning about 3700rpm at 60mph with 3.90 rear.
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By Eric - 7 Years Ago
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Thankyou for the response! Do you know what model 57/58 would bolt in?
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By MoonShadow - 7 Years Ago
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They went to the 9" in 57 so they pumpkin will not bolt in. The entire 57 rear axle is a close fit though but driveshaft and U-Joint mods are required.
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By RB - 7 Years Ago
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Eric I have a 56 rear I just pulled out 3.22 ,good drums, nice rust free one... Free for the taking.. Stevens point
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By DryLakesRacer - 7 Years Ago
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The gentleman who built my 56 used a 55 3.30 rear. Since I just went to a true 3 speed automatic my next project is to replace the entire rear end. From what I've read a 65-6 Mustang V8 is very close to a bolt in with the total width within 1/4-1/2" and what I've read and the spring perch being very close. Most I've found have 2.80 or 3.00 gears. I've found them complete with e-brake cables still on. Prices vary but after the new year it's my next purchase. Good luck.
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By MoonShadow - 7 Years Ago
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Cougar and early Bronco are narrow too. You may need to switch axles on the Bronco as its a 5x5.5".
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By Eric - 7 Years Ago
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Thankyou for the info. I will keep my eyes open.
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By Eric - 7 Years Ago
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RB Thank you for the response. I may have interest in that. Do you have photos or dimensions? Axle flange width? Spring perch centers? Thank you
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By RB - 7 Years Ago
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Eric Give me a day or so and i can get that to you.. It came right out of a 56 Victoria
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By RB - 7 Years Ago
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axle flange to flange 57" Spring perch center to center 42.25"
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By paul2748 - 7 Years Ago
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I realize I wasn't specific enough. I did mean the whole rear end housing. The 57-58 center section will not, as noted, bolt in to a 56 housing.
Eric (12/18/2017)
Thankyou for the response! Do you know what model 57/58 would bolt in?
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By Lou - 7 Years Ago
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I see problem here, a 3.90 gear should give you about 2700 RPMs at 60 MPH not 3700 RPMs. If you are turning 3700 RPMs at 60 Mph then your transmission is not shifting into high gear, check the Modulator and hose to it .
A 3.22 rear gear would give you 2350 RPMs at 60 MPH.
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By Ted - 7 Years Ago
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Eric (12/17/2017)
I have a 1956 ford Fairlane differential with 3.90 ratio. Would like to go to 2.90 or 3.0 What would be the easiest option? Is there something else i can bolt right up to same housing? It has 17 spline axle shafts. Thanks
The ’57-58 car 9” rear ends are pretty much a direct bolt in for the ’55-56 Ford cars. As mentioned, a different u-joint is required. The ’59 housings are the same widths but the spring perches are slightly more outboard. I have seen the '59 rears used with the springs being slightly arched outwards in the earlier Fords but I’ve gone to the trouble to simply relocate the spring perches on those slightly inboard in which to compensate.
The rear end housing in my ’55 Customline is out of a ’58 Fairlane and I used it in its entirety with the original ’55 emergency brake cables hooking up as they should. I did have to modify the stock drive shaft to use the later model u-joint.
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By Eric - 7 Years Ago
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RB Thankyou for the photos and measurements of your rear axle. It looks exactly what I have. If the ring and pinion gears are good and runable, I am interested in it. Also if you can confirm it is a 3.22 ratio. What is a good time and number I can contact you? Thankyou.
Eric
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By RB - 7 Years Ago
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email me at brechlrl@charter.net
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