With the T400, 2.93 is ideal. The torque is more than the tires can handle at launch yet it’s loafing at 70mph. You’ll get the same result (wheelspin at launch, abundant acceleration from then up, easy highwsy cruise) with the overdrive and 3.42 or shorter but you’ll spend more for what’s essentially one more shift. That said, if you’re not worrying about a budget, you might want to change the whole rear end to an 8.5; I’d ask Jim about your options. Patrick
As of two months ago,FabCraft was talking of getting enough names/interest in doing a run of 3:42’s. The 3:64’s would come with enough interest.
Hmm, maybe my math is wrong, but if I would go with 3.64 in 4th gear (TH200-4R), I would end up almost with the same ratio as my stock 2.56 in 3rd gear (TH400). 3.64x0.67=2.44 versus 2.56x1=2.56. Where would be the benefit of an overdrive? Just by locking the TC in 4th gear?
?? where wouldn't be the benefit? What do you want to do with a muscle car? You should have bought a Cadillac . You get everything low end and freeway and if you get a lock up converter another couple hundred RPM down again. I have the lockup on my 700R4, love it for freeway rides. You have to figure out what you want your car to do for you and pick your parts. I wanted a 12 sec ride that was not a big lobey unmannerly idle. And still be able to hit the highway for a show out of stated with out having to trailer it and have it nice and reliable not over heating etc. Next i am going to the A/C back. BUT this is my car... you need to decide what you want.
don't know about that one I know that the decicion is up to me, I just wanna get as much input as possible because I wanna do it right the first time. I know what I want: Keep or even slightly improve launch performance (thats the muscle car part) and enabling comfortable cruising (thats the Cadillac part). But there is one more aspect to consider: Inner city driving. The legal speed is 50km/h (31mph). So typically one drives in between 50-60 km/h (31-37mph), but don't quote me on that . I want to avoid that the transmission shifts all the time back and forth in between 3rd and 4th in this speed range. As the 200-4R has a more favorable ratio in 1st and 2nd I will be automatically better off in regards to launch. Every step I move away from my current 2.56 in the rear will even further improve the launchability. In regards to cruisin everything below 3.9 in the rear will be better compared to my current setup. About inner city driving: Nummerically (based on my math) I will be in 4th gear above 37mph with 2.93 rear or already in 4th gear at 31mph with 3.55 rear. My gut-feeling is, that in that regard I will be better of with a lower numerical rear end ratio, as above does not even take in account lockup in 4th gear. I know, I don't make it easy on you guys to support me, as my needs are somewhat different or even contrary to what you are used to. The more I appreciate every piece of input.
Why would you drive in 4th gear at 30 mph? You will get worse gas mileage. The car does have a gear selector so you do not need to put the car in 4 gear. I drive my over drive in 3rd gear trans selector till I get on the freeway then slide it in to OD. This way it does not shift into 4th unwanted cruising around town. You can have a tranny shop adjust the trans to tailor more to your driving needs also. Governor weight and even the cable plunger inside the valve body to control pressure flow. Just have t get a shop that knows what they are doing. Jim
I made it out to my Buick yesterday, as I wanted to find out what is currently installed, before ordering parts for any modifications. Beside of the fact, that fun is somewhat limited when you have to crawl under the car with temperatures below 32, I believe I made enough pictures to (with the help of the fellow board members) identify what I have installed. I do not know about all the identification-marks on the different parts. But what seems to be logical is the pinion where it says 16-41. If this is the tooth count of the pinion and the ring gear it will be the 2.56 ratio. But why would someone mark the ring gear with "64"? So here are the pictures and I welcome any insight from your end. In terms of the desired ratio for my application I am looking for either 3.23 or 3.42 with posi, depending on availability. Any offer is welcome. THX
1968-1970 Buick.... Is all you can tell from the pictures you took... Sorry Looks to be be all original.... If you said the ring is marked 16 - 41 that is a 2.56 looks like it is on the pinion crown ... It is open None posi bolt in axles 28 spline 64?? Do not know. definitely NOT a date. Jim
No worries, I am not disappointed, as you confirmed everything needed to know for ordering parts. THX
As long as you realize that the 68-70 8.2 is a Buick only rear and NOT the same as the 64-67 BOP rear. Plenty of parts for the earlier 8.2, but not the 68-70 rear. Lots of guys make that mistake, don’t be one of them.
You can get a posi from Jim or myself,but you will have to wait for gears. FabCraft has been talking of doing another run of 3:42’s,but nothing is scheduled yet. I sold both of my 3:23’s in the last month,so I don’t have anything used to offer right now.
I gave up on the Buick only stuff. I got a 8.5 now (from Everyday Performance), which arrived today. Also got a quickratio steerbox from carhex, which Ken was kind enough to also put on the pallet.
That is one thing I just do not agree with in the Fabcraft world. You sometimes just need to bite the bullet and run the gears...THEY will sell. I throw big money for the 12 bolt olds posi units and the 9.3 Olds /Pontiac Posi units I custom make too. It hurts some...BUT I have learned to pack some of the money made from the units back into a fund to make more again down the road. You have to be disciplined in a small business. Jim JD
Yea,with the O-axle,I always need something,so I’d rather have it on the shelf,instead of scrambling to make it.
