1961-'63 Buick Special/Olds F-85 rear end conversion

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I recently purchased a 1961 buick special with the 215 V8 and 2 spd dual path transmission. The rear is the stock rear(4 link) that has a leaking pinion seal. I measured the
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==Introduction==
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backing plate to backing plate as 51.5 inches. I have been researching a conversion for both the trans and rear and have still not nailed the proper components to satisfy my requirements. I want the car to be realiable, primarily!  I am planning on warming up the motor in the future so I do not want to install something in this car that is not stronger than the stock components and i also want to be able to obtain parts for it in the future if necessary.
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The 1961-'63 Buick Special with the 215ci all aluminum V8 and 2 speed automatic Dual Path transmission is the subject of this page. Pontiac Tempest and Olds F-85 were similar models.
  
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==Stock rear end==
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The stock rear end is a 4 link. The backing plate to backing plate width is 51.5 inches. The ring gear and pinion are very small, and although the rearend is light, it is weak. Add to that the fact that there is basically no aftermarket support for this rearend, and the reason for a swap beciomes readily apparent.
  
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The three main problems with this machine is that it is low, and does not have much of a tunnel to install larger components , therefore floor(tunnel) mods will be necessary to convert to larger, stronger units. The other problem is the driveshaft; it is 2 piece and not strong, as
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==Vehicle design considerations==
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i have read about folks taking a spare rear drive shaft with them in the trunk, just in case! And lastly is the bolt pattern on the block to bellhousing. The 215 is a special design that does not fit up to any other GM components. Rover bought the motor in 64 from Buick and there are parts available for MG conversions and others.
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The three main problems with this platform is that it's low to the ground, and it has a relatively shallow driveshaft tunnel in the floorboards. That makes using a different rearend pinion position or a larger diameter driveshaft more difficult. In most cases, floorboard tunnel mods will be necessary to convert to a larger, stronger unit.  
  
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D & D has adapters for using a BOP T5 5 speed trans and they also provide all the parts necessary for the swap. The other option is the TH200 auto trans, and D & D has an adapter for that conversion as well. The driveshaft will have to be modified. Any way you look at converting this car is expensive. Nothing is cheap anymore!
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Another problem is the driveshaft; it is 2-piece design and uses a center bearing/support assembly and is not very strong.
  
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I have been told that a Ford Fairmont rear from a late 70´s car is almost the same dimensions as the buick rear but in my research i have found that it is not a strong unit. That leaves some other choices and that is obtaining a 8.5 10 bolt with the eyes on the carrier or a 12 bolt with the eyes on the carrier, or a 8.8 Ford rear with the eyes on the carrier and have the housing cut and the spring pads relocated. The backing plate on the carrier has a radical angle that is not typical of the other GM cars. i wish this rear was a bit stronger and parts were available, because it is light!
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And lastly is the bolt pattern on the block to bellhousing. The 215 is a stand alone design that does not fit up to any other GM components. Rover bought the motor in 1964 from Buick and there are parts available for MG conversions and others.
  
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I have gone 2 routes since i started this page.
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==Donor==
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A 1978-'88 Monte Carlo 7.625" rearend is about 0.5" narrower than the stock Buick Special rearend. Other similar G-body rearends should work as well. Lower control arm brackets will need to be fabricated. A jig for the placement of the brackets will be a help in getting the correct angle and spacing. While this differential is not known for its strength, it is stronger than the stock unit, and can be upgraded by using a better aftermarket limited slip diff.
  
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I bought a 88 mustang 8.8 rear because it had the eyes on the carrier for the upper control arms. I later discovered that it was 4 inches too wide for the buick special. that is since gone, and then i purchased a 78 monte carlo 7.625 rear that is .5 inches narrower than the stock buick special rear. I made some lower control arm brackets and also a jig so that the placement of the brackets would be at the correct angle and spacing. The rear is in place now and fits great. I installed a powertrax differential before placing the rear under the car. I reccommend using 4.75 backspacing wheels or 5.00 bs wheels to get the proper fit in the rear wells.
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===Other possible donors===
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It has been said that a late '70s Ford Fairmont rearend is almost the same dimensions as the Buick rearend, but its strength may be limited. That leaves some other choices like obtaining a 8.5" 10 bolt with the control arm "eyes" cast into the carrier, or a similar 12 bolt, or a 8.8" Ford rearend (also equipped to use control arms), and then having the housing cut and the spring pads relocated. It has been found that a 1988 Mustang 8.8" rearend is 4 inches too wide, but could work if narrowed.
  
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I am now in the process of swapping out the dual path transmission to a 96 camaro T5 that i re-welded the tailshaft mount straight instead of the angle that it had for
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==Wheels==
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the camaro/firebird mounting. I also had to re drill the bellhousing i bought (shroeder) and make a lower adapter for the T5. i chose to fabricate a cable clutch linkage because there just is not any room on the firewall for a master cylinder. I think that the cable will work fine and is easy to set up and adjust. if you would like to see photos, just email me at the above address.
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===Wheel bolt pattern===
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The original Buick wheels are 4 on 4-1/2" pattern. The GM rearend uses a 5 on 4-3/4" pattern. The axles can be redrilled to reuse the original 13" Buick wheels, or the front drum brakes can be changed to a 5 bolt pattern or better yet, swap the front drum brakes to disc brakes having the correct 5 on 4-3/4" pattern to match the replacement rearend. Or two different spare tires can be carried.
  
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Today i attempted to install the T5 from the 96 camaro, and there is no way it will fit without removing a good portion of the tunnel which is what i did. now it is in and the shifter is almost in the perfect location. I am going to hunt for a hurst lever, to give it that old world look and put it in the perfect location for me. As you can see i am into the old school, innovation in action crowd.
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===Wheel backspacing===
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A 4.75"-5" wheel backspacing will give a good fit in the rear wheelwells when using the 1978-'88 Monte Carlo rearend at the stock width.  
  
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[[Category:Undeveloped articles]]
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==Transmission adapters==
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[http://www.ddperformance.com/shop/product_info.php?products_id=206cPath=111_137 D & D] has adapters for using a BOP bellhousing with a T5 5 speed manual transmission along with all the other parts necessary for the swap. Another option is to use a TH200 automatic transmission; D & D has an adapter for that conversion as well. The floor tunnel along with the driveshaft will have to be modified. 
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Clutch linkage==
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A fabricated cable clutch linkage is one option because of the lack of room on the firewall for a clutch master cylinder. That said, there may well be a way to use a hydraulic throw out bearing w/a remotely mounted clutch master cylinder. If you can find it, the 1963 Skylark with the Borg Warner T10 4 speed clutch pedal and linkage can be used  with a conventional throw out bearing and arm.
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[[Category:Rearend]]

Latest revision as of 09:37, 11 September 2023

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