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

==Introduction== 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. ==Stock rear end== 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. ==Vehicle design considerations== 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. Another problem is the driveshaft; it is 2-piece design and uses a center bearing/support assembly and is not very strong. 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. ==Donor== 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. ===Other possible donors=== 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. ==Wheels== ===Wheel bolt pattern=== 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. ===Wheel backspacing=== 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. ==Transmission adapters== [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. Clutch linkage== 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. [[Category:Rearend]]

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