Hello. I am new to the forum, I have questions about installing new gears for my 1972 skylark custom convertible. I am debating whether the 3.55 or 3.73 would be worth installing. As far as gains on the strip are concerned, how much time can be shaved off by installing a 3.55 or 3.73 compared to a 2.56 ( will be running a 26.5" diameter tire ) I plan to install an posi carrier , which I am sure will require a taller gear. Still want to be able to cruise and drive on the highway without running a really high rpm. I had considered installing a 700r4 to gain that fourth gear/ overdrive so that I could still run a 3.55 or 3.73. NAy thoughts or input on the gear change or ratio ? I appreciate any input. I recall that my 1971 pontiac lemans had a 3.31 gear , fairly quick and didn't run real high rpms on the highway. So I am looking for a good compromise. The old school muscle car mechanic I recently met suggested the gears and 700r4. I am sure that I can find a good used 700 r4 transmission from a 1980's fbody, firebird , camaro, 2wd blazer ,etc. Of course this means more expense and time, etc. Thank you for your input.
The 200R4 trains is a much better swap than a 700. The 200 is almost the same length as your th350, same spline count input, and has a Buick bellhousing patern. The 700 requires a different spine input shaft, different length driveshaft, and an adapter to convert to Buick bellhousing patern. There is a step by step how to instal 200r4 thread by ken who owns everyday performance, contact him or do a search under his user name which is techg8 I think. Decide if you want the overdrive trans before you pick a rear gear. If using an overdrive I suggest 3.73 or if not using od then a 3.42 is your best bet. I have a 4.56 gear and 32" tall tire and it's still okay at 130 mph lol just a little hard on fuel. No overdrive yet but going to swap in a 4l80e from a 1 ton gm truck.
Thanks Sean for the suggestion and the info. I did a google search and found quite a few gm cars that came installed with a 200r4, should be relatively easy to find a good used one in my area. Sees like it would be a fairly easy diy install as well. I found a lockup kit by ron francis on the summit website, I am sure I could find a bracket adapter. I had planned on an aftermarket shifter, so I am sure I could use a b and m shifter ( which will take care of the shift indicator issue) , install a transpak or shift improver kit and a higher stall torque convertor. So that just leaves the issue of the trans crossmember, I assume there will be an adapter available for that ? or just it bolt right up ? Thanks, Chris
2004r bolts right to the stock cross member. You just have to move it to the rear holes that are already drilled in the frame. Also as far as the neutral safety switch you may get lucky and be able to use it with the 200. I've had my stock switch in the car for 20,000 miles and it still works fine. And I used to manually shift the car with the column shifter all the time. I would look into the different companies out there that sell built 2004rs. Even behind a Buick 350 you run the risk of burning that transmission up under abuse if it's a used trans. The piece of mind of having a new trans is worth it. As for gains you will see with 3.73s, If you can find traction you can see as much as half second in the quarter. Depends how well you have the car set up. I went from 14.9 with 2.73s and a 4bbl holley to 14.1 with 3.73s and a q jet(different track so that helped me pick up some time too). I used 27inch slicks.
If you stay 3spd then 3.23 or 3.42 for anything but all out track use. If you are going to go OD and you have any cam at all then go 3.73.
The 3.55 will obviously give you more torque multiplication than a 2.56. But if you already have enough power to spin your 2.56, then why would you want more torque multiplication? You'd lose the nice low highway RPM's. But if you are going to put slicks on the car, and you won't spin with a 3.55, then it will gain you about 0.15 seconds in the 1/4 mile. -BC
Hello everyone. Thanks for your replies. Certainly very helpful information. Should make it easier to make a decision. I think my best bet is to swap in a 200r4 trans, a DIY proposition once I find a the tv cable bracket from somewhere , I found a lockup converision / wiring harness from Ron Francis on Summit's website. Then I can add a 2500 stall converter, to put it in the right range for launch. I plan to add a set of anti hop bars, run a centerline or steel wheel for the back with a cheater slick 27-28" diameter , maybe 8-10" wide ? Any thought on using an caprice classic setup for rear discs ? or using a police spec set of drums ? I'd have to make sure that the bolt pattern is the 5 x 4 3/4 ... Looking to improve the brake system with breaking the bank. i know a chevy s10 blazer disc setup would work , 5 x 4 3/4 bolt pattern too , with a parking brake.. just need to fab / add a caliper bracket.. with some good pads , slotted rotor , should add some good braking power. I could probably use the e-brake cables as well, since they are operated by a foot pedal... anyone here ever used a heavy duty drum setup ? With a drum / drum set up , I wouldn't have to change my master cylinder..
http://m.summitracing.com/parts/tci-376700?seid=srese1&gclid=CKiXr5_LvcgCFdUTHwodeQAFxw This is the bracket I use for my qjet. Keep in mind that you must have a TV arm with the correct angle on it on your carb to allow proper TV cable travel. Otherwise that transmission will be coming out again in short order. Some have suggested securing the TV cable to the kick down slot on the throttle pedal. I haven't tried it myself but it's worth looking into further. The best thing to do for wheel hop in my opinion is to have rear suspension bushings that are good quality in the rear and the correct driveline angle. I've never really had wheel hop issues in my car whether smoking the tires or catching traction on slicks. F41 rear suspension brace bars are highly recommended to keep you from ripping your rear crossmember out. If you really want to go crazy, replacing the flimsy stock upper control arms with adjustables and boxing the lower control arms will add quite a bit of stiffness and further reduce risk of wheel hop. There are other factors like rear ride height, coil springs and shocks that can hurt or help you as far as traction is concerned. I'm being very vague but there are others here that have much more experience than I on the subject. I'm just listing what has worked for me. For brakes, if you don't already have power front disc brakes you should look into a conversion kit. They are reasonably priced and comes with everything you need to make the conversion. I went from manual drum to power disc and it was a night and day difference. As for rear brakes I've found the stock rear drums are adequate in most situations. The biggest benefit for using rear discs would be axle retention if you happen to use a Chevy rear axle that uses c clips. For a Buick 8.5 rear the axles are bolt in so you shouldn't have to worry about it. You should also consider what your goals are now and in the future for your car. It's best to chose a stall speed, rear end gear and camshaft or at least have in mind what cam you want to use so that you don't have to change everything again when you make the swap.
Regarding the lockup converter, to save some money you can just wire up the lockup converter with a toggle switch and a brake switch to unlock it if you hit the brakes as the engine can stall when braking. When you get to that point we can help you with the wiring, but there is no need for a wire harness or kit you can wire it yourself. I have used the lockup kits and prefer to just have a toggle switch on the dash to control when it locks up. For the TV cable just have Ken or Mark Northcut build you a Q jet with a TV arm on the linkage. Or go with a Holley which ever you prefer.
Lots of discussion on methods of locking the converter of which there are about 10 different setups depending on what level of interaction you want to have with when it engages/disengages. There are aftermarket throttle arm connections that are easily added to Holley and Edelbrock carbs for the TV cable hookup. The brackets for the TV and throttle cables are plentiful but beware, cheap flimsy TV mounts will flex under load and can cause problems.
700r4 has the same yoke as a 350th and the 200R4. Jim 700 is longer and for BOP you will need a mid plate. IF you are swapping a stock built for a stock build 700 is stronger than the stock 200 you would need a aftermarket or GN 200R4 setup if you have some torque out put. BE careful with too many used parts as the parts your buying used are getting pretty old now... last time they used 200r4 in cars was 1990 B-body cars... I personally have a 3.55 and 700r3 trans in a Monte Carlo 212 duration cam @.050 great low end and freeway is way more top end than the NEW suspension of a 1971 will deal with...lol. :0 best combo I have ever had love driving the car ... Soo being you have a 10 bolt 8.5 you have 3.23 3.14 3.73 3.90 4.10 gear choices. If you are not doing over drive do 3.08 or 3.23 it will be a big enough change to make you happy... If you are doing over drive and you have a good torquey stock-ish type cam 3.42 will be best if you have a healthy cam 225-235 duration @.050 3.73 and if your cam is above that duration you might as well race your car too much duration for reasonable street driving... AGAIN I am sure there are guys driving on the street with more duration... Being real, that is not really normal street driving duration... Have fun with the car... Jim J D
