Landracing Forum
Tech Information => Steering - Suspension - Rear End => Topic started by: floydjer on February 04, 2008, 10:20:59 AM
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Greetings....A noob w/ a question. What type of dif. is preferred and why? If this has been covered already, please steer me in the right direction. Thanks in advance. Jerry
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This has been covered many times and I don't know where tyo find it in the site.
With that said long wheel base cars seem to live with anything. With all others: if you have a locked rear and spin, take it out. if you don't have one and spin, put one in..........Listening and learning over the years...JD
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JD---this is a good example of why you should keep posting---and not go ONLY pm---thanks for your input!!!!!!!!!!
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Having run an open rear-end in a short wheelbase Monza with some sucess , A spool or locked rear end in a variety longer wheelbased cars, again with some sucess, we tried a "locker type" configuration as recommened by the Winters Rear End people. We had problems right off the starting line with what seemed to be the locker sending power from one wheel to the other - not a good deal. I am not sure what brand of "locker" they put in the quickchange but it sure didn't work for us.
Has anyone else had a good expierence with type of "traction control?? - Pat Kinne
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Pat, To my way of thinking, run an open or spool. When a locker screws up it really is a hand full. Been there, done that. lol Doug Odom in big ditch
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Pat, When I spun my Lakester in '05 at El Miriage---I went around asking as many people as I could find that I knew to have be around for a while, about "OPEN" or "SPOOL".
The bottom line consenus was: If you have a spool and have problems---switch to an OPEN- :-D-If you are open and have problems switch to a SPOOL!!!! :-D!!!!! I would like to add if you have done all of the above and are still having problems- :evil: :evil:-check your "SCRUB RADIUS"---I hope that this solves the problem, as I have tried it both ways!!!!!!!!!!! LOL
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I too have asked around and got the same response as Sparky. What works for me may be totaly wrong for you. I run a spool and am happy at this point. Vince
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I would not recommend a locker...still shuttering from a triple loop 30 years ago. If a quick change customer wants an open dif, I recommend the Winters Track, it is a worm style posi without clutches. It senses which tire has the bite and applies the power to it. For what it's worth!!!
joe
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Thanks guys - Thats how this forum is suppposed to work - good information from people that have been there and done that - Great.
The bottom line is that we will be going to a locked rear end for this year - all things concidered, we know that will work and get you done the track. Your point of "problems with spool change to open - problems with open change to spool" is well taken - Thanks for participating - Pat
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Pat, I know you know this but for anyone new there are other things that effect the rear tires also. Be sure that both rear tires are the exact same circumference and air pressure. Weigh the car on 4 scales to be sure you don't have any cross weight. Your not going to pitch it into a corner so cross weight is bad. check toe on the rear axle also.
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I was just reading along but the last comment about checking rear toe got my attention. What is rec. for rear toe for bonneville in a sedan bodied car ?
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What about us FWD guys? :lol:
I started in 2004 with a welded diff (no money) and it worked great with 160 HP to the wheels. I got some cash and bought a quaiffe LSD. This was in 2005 and I had 540 HP to the wheels and the salt was god-awful. As I hit soft spots and hard sports with each front tire, the car would dart off to the other side due to power being put onto the "good" wheel. I literally almost hit the 3 mile marker and the 5 mile marker flags. I got out of the car shaking. In 06 I changed to a spool (welded diff + cash = spool) with 540 HP again and blew the motor up before I got a definitive answer to the question. I have since talked to a few other high HP FWD guys and they swear by open difs.
In short, All I know for sure is that the salt sucked in 2005 so I am going to try the spool again this year as it's already installed in the trans.
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Topics like this are what makes this Forum GREAT.
Coming from a Drag Race background I had preconceived ideas that a Posi was best. I run a 300" carb'ed gas engine so less affected by large torque #'s. I'm running a 700R4 with 4:88's. Worked good @ Bonneville but at El Mirage if I have to lift in OD the engine drops off the curve and will not recover @ top end.
I talked with Mark @ Pro Gear about building a third member with a 3:40 gear set and only using the first 3 gears @ ElMo. He asked me why I wanted a "Posi" which caused me to pause. He said that the majority of guys are running open rearends so that's what I'm running this year.
Like JD says, if it doesn't work I can always switch back.
We had a Club guy with a real torque monster. Always wanted to go left. They were running a Posi. At Bonneville 2 years ago they pulled the Posi and went to an open Dif. Still had the problem. Turns out the tires were mismatched. Went to another set that were matched for circumfrence and went straight.
So many variables!
Tom
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Topics like this are what makes this Forum GREAT.
.................................I talked with Mark @ Pro Gear about building a third member with a 3:40 gear set and only using the first 3 gears @ ElMo. ...............Tom
I'll bet you do better. I have a 700R4 in my truck and love it, but the 30% drop on the 3-4 shift is a killer. I recently got a 4L80E rebuilt that will go in the truck next winter with the anticipation of running it for time only. When I do I'll change rear gears and just run the first 3 like you are talking about.
c ya,
Sum
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Current thread on the same question.
http://www.landracing.com/forum/index.php/topic,3696.0.html
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Hey Sum,
My daily driver is a '57 Chevy 210 with a 327, 700R4 and a 3.70 gear. Freeway speeds @ 2,000 RPM but with the steep first gear accelerates pretty good and gets about 18 MPG.
I have an alum. head 383 on an engine stand but with gas prices what they are I may leave it there a while.
Tom
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Hey Sum,
My daily driver is a '57 Chevy 210 with a 327, 700R4 and a 3.70 gear. Freeway speeds @ 2,000 RPM but with the steep first gear accelerates pretty good and gets about 18 MPG.
I have an alum. head 383 on an engine stand but with gas prices what they are I may leave it there a while.
Tom
My motor has been a mild 290 HP or so 350 with 3.50 gears, 28 inch tires, 700R4 and Q-jet and I've been getting right at 20 without the teardrop and 16 with it running 75. In the process right now of putting the new motor in with AFR heads and a bunch of good stuff so that I can turbo it next winter. I hope I don't totally kill my gas mileage.
It will have the carb until next winter then I'm going EFI,
Sum
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Same topic in "Steering - Suspension - Rear End" above.
Same conclusions.
Jon could these 2 threads be merged?
Tom
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Tom, We "moved" it to Rear ends just so the research might go better---just trying to "make" FOURM work better---sorry for the confusion---next time will try to eliminate the confusion
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John, FWD with a spool would take a braver person than I to drive. If a CV joint or half shaft has a problem the drive will have a real big problem. I believe that is what got Dean Johnson upside down a few years ago.
Doug Odom in big ditch
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After just reading this thread for the first time, I noticed that there was no mention of making sure that both of your back tires have the same circumference when you're using a spool. It makes running in a straight line a lot easier.
Dave
http://www.roadsters.com/
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Just a note for FWD .... if you run extra "negative" scrub radius (get the contact patch well inboard of the kingpin) you'll get a counter turn effect should an axle break, or even loss of traction on the opposite side. The drive on the wheel with traction tries to turn the wheel in the opposite direction of the "cross pull" from opposite side traction loss.
The import drag guys started using this in the late 90's and it did help keep some cars off the walls. They also saw improvement in tracking as the front track became narrower (limited by turning clearance at the end of the crankshaft or trans case). It's a tricky job on many front ends, because you have to convert from strut to double a-arm and the spindles may have to be fabricated from scratch (to reach far enough inside the front wheels for extreme scrub offset).
I also have a question about live axles, if anyone has an idea. Does the long axle provide less torque, than the short axle, on a typical rear end? I know from my air tools that every bit of extension takes away available torque at the socket. I suppose it's not enough to matter...but I sure don't know the answer.
Thanks!
JimL
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I echo the tire deal as well. I was running a mini-spool with Mickey Thompson bonneville tires and was straight and easy to drive. Looking for some more, switched to sl taller front runners, same pressure and it was definite squirrelly and needed to drive it, not just point and stab the throttle. My engine makes maybe 130 tq at the wheels so wheel spin not such a big deal. Maybe a higher pressure would have helped.
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JimL the longer shaft just has more torsion spring to absorb the impacts trip hammer shocks---the counter force of the drive shaft rotation is the force that gives the right rear tire on a car less traction than; the longer axel will help tractive effort---ie the longer lever resisting the effort to pick up the tire :-P I THINK
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Thanks for the thinkin', Sparky, I'm puzzling the engine location for my roadster, today. The pinion on the diff is offset to the right (axle shafts are equal length), so I have to offset the engine/trans to keep the driveshaft pretty straight. The driveshaft is only gonna' have about an 8-10" tube, so I think I'm stuck with positioning "stuff" to get the car balanced.
After reading the posts about tire sizing and corner weights, I'm going to have to be much more careful. The engine if HEAVY in this project. Hopefully I can juggle batteries and ballast and make everything come out right.
I really appreciate all the notes passed along from the long-time builders. How in the WORLD did we get along without the internet?
Regards, JimL
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Doug, If I'm not mistaken I believe "part" of Dean's CV joint problem was lack of maintenance. It was quite apparent when we loaded it in his trailer prior to leaveing the salt at the end of the meet. CV joints in off road have looked to be pretty good with the abuse I see they get in the 4 wheel drive class. Good luck.........JD
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John Romero, any conclusion on front wheel drive with spool? My FWD lakester moved around alot at SW and I concluded that it was salt condition in combination with my me not having enough balast on the front. Last year with a C engine had no wheel spin in low, but this year they would spin like crazy unless I pedaled it. I have a B engine and didn't ad any balast cause I was just trying to go 'just" 5 mph faster. I think I went over the edge. Any thoughts as I have a spool also.
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What is your scrub radius?
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Scrub radius is right at 3/8". Car went fairly straight last Oct. but have added some Tq and HP. I'm thinking wheel spin was moving car around and as I corrected it the caster would load the tires unevenly and create further problems. I plan on putting in about 400#s of lead in front and put my car on electronic wheel alignment equip. to be sure every thing is pointed sraight. I read about rear tow in. May be something to look into. Still thinking it is wheel spin. How much wieght did you ad to rear Sparky?
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Several articles on scrub radius on google
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John Romero, any conclusion on front wheel drive with spool? My FWD lakester moved around alot at SW and I concluded that it was salt condition in combination with my me not having enough balast on the front. Last year with a C engine had no wheel spin in low, but this year they would spin like crazy unless I pedaled it. I have a B engine and didn't ad any balast cause I was just trying to go 'just" 5 mph faster. I think I went over the edge. Any thoughts as I have a spool also.
Made a bunch of passes with no handling problems at all. The car was very stable at all speeds and didn't get upset when I lifted, pulled the chute or anything. Despite "explosive" boost application and ridiculous amount of wheel spin the car was actually very drivable and confidence inspiring. All in all it is working very well so I am going to leave it in. With that said, I do have a significant amount of front ballast (200+ lbs) and a very stiff suspension setup.
Doug, I hear what you are saying about the axle breaking problem and the likely results. I have installed a really nice set of custom axles that I feel can handle any amount of torque I could throw at it. Plus I inspect the whole front end and driveline very closely before each event. I *think* i'm OK in that regard :-P