Slant Six Forum :: Drag race rear end build

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Drag race rear end build https://www.slantsix.org/forum/viewtopic.php?t=5973	Page 1 of 1

Author:	Rob Simmons [ Wed Jun 11, 2003 7:53 am ]
Post subject:	Drag race rear end build
I know that a 7 1/4 will survive behind a mild slant 6 and that it is lighter than most other rear ends... I will be running the 7 1/4 probably all season. I want to start building a better/stronger package for next year though. It will be strictly a drag race car that won't see any street time. We may take it autocrossing later. I will probably wind up buying a B body 8 3/4. I am seeking advice from people who have drag raced and have Race Proven opinions on what works and what doesn't. Here are some basic questions... 1. Is it really all that critical that I get a 489 versus 742 or even 741 pumpkin? I have a couple different pumpkins to choose from. There are actually parts and gears becoming available for the 741 and it's not like I am running a Hemi four speed 2. Should I build two pumpkins (one geared for 1/4 mile and one for 1/8 mile) or is there a decent ratio that suits both? What ratio do you recommend? 3. Should I just run a spool? It saves a little weight, is cheaper than a Sure Grip, and doesn't have to be rebuilt. 4. Are the "green" bearings strictly a drag race only bearing? Should I try to stay with adjustable bearings since I "might" try autocrossing this car? Opinions on this one vary greatly. 5. Stock axles should survive fine, right? I will be running slicks at some point. 6. What else have I forgotten to ask or what else do you want to share? Thanks in advance every one. Rob

Author:	GunPilot [ Mon Jun 23, 2003 10:15 am ]
Post subject:
Well, since nobody has replied to you, I thought I would offer MHO on some of your topics. These are not necessarily (bold) race proven, but I do have some experience with the Hotchkiss-type rear end. I think at the power levels you are going to be working with, any of the cases will be fine. I think having multiple pumpkins on hand is a good idea, because this axle makes them so easy to swap. What ratio you use will be determined by what RPM you wish to be turning at the end. Maybe some of the hardcore racers here can offer advice on this. Also, you will almost certainly want a different gearset for autocrossing. I have a 3.55 in mine, and a 4.10 or 4.56 would be better for my heavy Duster and mild slant on the 1/4 mile. 3.55 is great for around town though. A spool is fine for the 1/4 mile. A Suregrip would be better for autocrossing. I think the locked rear would make it push (understeer) quite badly under power. I installed, and highly recommend, the Green bearings. FWIW, design-wise, they are identical to the sealed-bearing type setups found on the Ford 9" rears used in cars. I used this setup (in a Ford 9") for my 3400# Chevy circle-track car, running a 450+ hp 383 on a dirt track. This bearing design proved extremely rugged, and I never had a problem with it. Stock axles should be fine. Unless you push your slant to very high performance levels, this axle is actually heavier (in weight and in strength) than you will ever need. If light weight is a major consideration, then you might consider an 8 1/4 axle instead. The only reservations I would have with one of these is it's c-clip axle retention for autocross use. Cha-ching! .02 please.

Author:	Rob Simmons [ Mon Jun 23, 2003 10:46 am ]
Post subject:	Thanks!
Thanks GunPilot, The experience with the green bearings is especially appreciated! Many people, including sellers of the bearings, have recommended that they be used for drag race only because they don't offer good lateral support and fail quickly under much cornering. With what you posted I'm not nearly as afraid to run them! Being an Arizona native I miss the dry weather, but it's looking like it's been a little too dry lately. Mount Lemon near Tucson is going to take a long time to recover. When I was in the Tucson Chapter of the Slant 6 Club back in the early 90s we made a couple trips up that mountain for car shows and cruises. That's a shame. Rob

Author:	GunPilot [ Mon Jun 23, 2003 10:57 am ]
Post subject:
I'll grant that the bearings are not as strong as the tapered design that comes stock. Tapered bearings are used in the Ford 9" axles used in trucks too. But the retaining plate that holds the bearings in place on the Green bearings is thicker and stronger than stock. That's what failed on my stock bearings in my 8 3/4. The bearing was pulling right through the steel plate as the axle tried to come out. I have seen this same thing happen on both types of bearings on the Ford axles used in circle track.

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