Quick-change differential

[Eric47Dodge]

Am in process of pulling my rear-end to install lower gears (now running 2.42, which has proved to be too high for my purposes -- car runs 80 mph in 2nd, but won't pull to red line in 3d). Am thinking of installing a quick-change rear end as long as I have the unit out, but new ones are too expensive -- seems like they're more than $2K. I could probably get away with $800 before my wife came un-stuck, and am wondering if anyone has a good used unit laying around in the shop that they'd care to unload. I have a pathological aversion to buying off e-bay or similar on-line source. Also, a guy told me that my fluid drive bleeds HP, and that I should weld it up. He says worst thing that can happen is that it breaks and goes back to being a fluid drive. Thoughts?

[John Burke]

I don't have one anymore but I have had chances to buy them at swap meets around here for 4-6 C's...The trouble is most of them will have a spool in them from when they were used for circle-burning so you still have to scrou8nge for internal parts....tough to find a cheap deal in my experience....John

[greg g]

I would doubt that the fluid drive is sapping much HP, probably more due to rotating mass inertia than loss through the fluid. the were engineered to be 1 to 1, reality is probably 1 to .95/.96. Check out Winter's Performance. They show a center section, to build yer own using ford 9 inch tubes and axles. Could be a more economical way to go.

[Brad Lustig]

Plus, Fluid Drive is usually a big conversation point. Much cooler to explain fluid drive and then show them, than to say "Well, before I welded it up, this is how it worked":)

[Plymouthy Adams]

I don't think that it is of any great concern regarding loss of power...they used this system for over a decade. On the other note....don't fix anything that works...get real..the little advantage versus the time and expense is just not cost effective..you'd be better off practicing your repsonse time for a consistant .5 second....

[greg g]

Hey Tim, I don't think they care much about reaction time on them dry lake salt flats record runs........Not pulling top rpm in high gear is a concern in that regard.

[Plymouthy Adams]

me bad..did not the intended purpose of the suggested repair was time trials

[martybose]

I wouldn't think you can even install a quickchange unless you are removing the stock gas tank; they do have a considerable overhang behind the axle. They also tend to be rather noisy, since the spur gears are straight cut. And I would agree with an earlier post that said most have spools in them, and lockers or limited slip differentials are rare and expensive.

Marty

[Eric47Dodge]

Threw out the stock tank when it started leaking. Car has an 8 gallon fuel cell in the trunk and a smaller "fake" tank from a junk yard mounted in place of the stock tank. I cut the top out of it because the sump of the fuel cell hangs down below trunk floor (through a hole I also cut). This car will never be stock, but I don't have the patience to restore it the way a lot of guys do, so just try to make everything work at the same time.

[Brad Lustig]

I didn't know the circumstances so I'll retract my statement about fluid drive for you. Might be worth it to you to lock it up

[greg g]

I would think the fluid drive would lend itself well to low numerical gears of land speed cars. Seems like the fluid coupling would allow the engine to do its thing while the gears catch up, rather than putting the strain on the clutch. Seems whenever I see a video or show regarding lakes/salt runs, the push trucks help get the cars up to speed and then when the shift occurs, the engine looses a lot of rpm almost sounding like it's lugging against the next gear. Seems the fluid drive would be in its element uder these conditions.

[Don Coatney]

I would think the fluid drive would lend itself well to low numerical gears of land speed cars. Seems like the fluid coupling would allow the engine to do its thing while the gears catch up, rather than putting the strain on the clutch. Seems whenever I see a video or show regarding lakes/salt runs, the push trucks help get the cars up to speed and then when the shift occurs, the engine looses a lot of rpm almost sounding like it's lugging against the next gear. Seems the fluid drive would be in its element uder these conditions.

Greg;

Having raced on the salt my experiance tells me that the traction loss from the tires to the salt allows more than enough "slippage". Best bet to acheive best top speed is to have a drive train that does not allow slippage.

[Normspeed]

Eric, Don, Pete, and whoever else knows this stuff, I'd be interested in a thread about what it takes to run in a stock class car at Bonneville. Safety requirements, allowable mods, cost to enter, stuff like that.

[greg g]

http://www.scta-bni.org/