LSD Preference

[Deleted member 3577]

Clutch, Gear Type or Viscous Coupling? I have read a lot about this subject. What I want to know is: How many of you have tried 2 or more and what do you think? How often do the clutch types need rebuilding? I have heard that the Quaife type may not be as smooth as the clutch...Is this your experience? I can't find anyone who makes the viscous type. I am leaning toward the Tran-X do you think this is a good choice? The application would be Elva Courier MkII 1400lbs and 135hp mostly for auto cross

 

[aeronca65t]

The racing Sprite I drove in a 4 hour this weekend has a Quaife. It has been in that car for a long time (years) with no problems under the most difficult conditions. We were getting light wheelspin in one bumpy turn, but that was probably because both rear wheels were off the ground.

I have driven cars with welded diffs, but I do not like them for roadracing. I did have one in an auto-x Spridget many years ago and it wasn't too bad for pylon-racing.

My own race-Spridget has a stock open diff. It's OK at higher speeds, but not so great on the second gear corners.

No experience with the other types.

 

[Bugeye58]

I've run Salisbury, Quaife, and Tranex, and prefer the Tranex. It seems to be a little smoother than the Quaife, and has been super reliable for everyone I know running them.
Are you running an MGB diff in the Elva?
Jeff

 

[Deleted member 3577]

The Courier MkI & II (58-61) uses a Riley 1.5 rear w/ Morris Minor axles. The diff is Sprite although many replace it w/ MGA because they can take more of a beating w/o double bearing hubs, and stronger axles. I prefer to keep things as much the same as possible. Elva mated a B series engine w/ an A series rear? ( I guess the BMC engineers, Through thier extensive product testing might have been appalled)

 

[Matthew E. Herd]

I was autocrossing last weekend and am now diagnosing a problem. I noticed a larger than normal clunk on taking up drive, but dismissed it as "that's normal!" I then went broke down on my first run, pushing pretty hard. Essentially, after a thunderous clunk, the car no longer drives. It shifts and clutches as normal, but I get clunking sounds when I attempt to drive. This leads me to the differential. I am also fairly sure that the clunk actually came from behind me (therefore it's the differential). I'm going to verify this, but I am now doing research about LSD selection and differential rebuilding. Ideally I would like to be able to immediately swap the differential assembly so that I could drive the car ASAP. I can work on rebuilding the differential in the mean time, but have limited time actually in the presence of my car.

I was thinking of getting a differential assembly and rebuilding it, but do not have any instructions on how this is accomplished. Also, I have long been interested in quaifes, but they run at least 1200 bucks. I saw that rivergate restorations has phantom grip LSD's for only 300 dollars. I honestly don't see how I can justify 900 extra dollars so long as both wheels spin when I stomp the pedal. Any advice is greatly appreciated!

 

[JohnnyB1275]

The noise could be with your driveshaft or your universial joints. I am starting to hear the same noise on my street car. I thought it could be the transmission mounts too. I'm building a race rear end now with my dad, not to sure if we're going with a welded or LSD. I'll take some pics along the way and make a thread going over the build /ubbthreads/images/graemlins/smile.gif

 

[Matthew E. Herd]

I have not looked extensively yet, but I'm 90% sure its not the driveshaft/U-joints. If the car does not go and there is no shaft hanging down, then it can't be that.

 

[aeronca65t]

Matt:

You've almost certainly snapped an axle.
Very common is Spridgets.
I snapped one last week myself at Summit Point (I still hadn't gotten my racing rear fully assembled). If you snapped an axle at the diff-end (by the splines) it's usually from too many drag-race starts.
The heavy duty axles (~$275 USD each at Winner's Circle) will fix this.
If it snaps at the outboard end, it's from the heavy loads related to turning/cornering...the only real solution is the double-bearing hubs (~$650 USD)................or drive slower. /ubbthreads/images/graemlins/jester.gif

 

[Matthew E. Herd]

Awesome, thanks Nial! I was coming out of the last turn to the finish a bit too hot and I (for some reason beyond me) decided to clutch the car. I believe that once I realized I could make the finish line without slamming the cones, I probably dumped the clutch at speed (with the engine at idle). If the axle snapped, it could be at either end because I just got much better tires (the Yokohamas I've been talking about) and they allow me to corner harder, accelerate faster, etc. I was also pushing really hard for a first run ... any weak link in the drivetrain was sure to go. As to the Winners Circle stuff, I was very unhappy with their panhard rod kit, and their 'assistance' was not so good. I also found that their radius link kit would not fit and simply returned it, but it took a very long time (about 5 months) to get a refund. That may simply be an oversight, but their 'kits' don't seem (with the exception of the swaybar kit, which was quite nice) to fit 1500's very consistently. I am hesitant to purchase axles from them when I hear that there are variations from year to year.

I'd like to know about more bearing kits, etc. Jeff had spoken about getting wheel bearings from NAPA that required minimal modification, but I failed to write it down and it was probably too long ago to search for it. Did you purchase axles from W.C., and what kind of rear are you building? I wasn't planning on doing anything to my differential until now, despite my evident wheelspin problems coming out of tight corners, but now it looks like I'll have to.

Thanks for the help!
Matt

 

[Matthew E. Herd]

One further question ... What differential ratio do 1500's have? My moss/VB research indicates that they may have 3.73 ratios, but my Haynes manual indicates that all spridgets from some VIN through 1500's have 3.909's. They make no mention of 3.73 differentials, so I'm inclined to believe that they are mistaken on this detail, but I would like confirmation. Thanks,

Matt

 

[aeronca65t]

Yeah....Winner's Circle is a sort of a one-horse shop. I haven't bought a thing from them....I've talked to them on the phone and they are pretty informal, so maybe that's why. I do know that one of the guys got hurt last year. Maybe that slowed them down.

Anyhow, I've built my own double-bearing rear and "trued" the rear axle at the same time. Lots of shop time to do this stuff. I also trimmed the bottoming blocks on the rear so I could drop it more.
I built my own panhard rod after I saw the Minimania unit (I didn't care for it).
As for axles, I have about 6 stock spares right now. I've Maxnafluxed them and they are all good so far. I fixed the car at Summit Point, but the axles that are in it have both been raced on single bearing hubs so I'll pull them both and used some of the others that have only seen street-use.
The yellow car that I also race (#23) has a 100 HP 1275 and it has d-b hubs and stock axles with lots of races on them...the double bearing hubs make the real difference.

For some good parts sources, try here:

https://www.mgcars.org.uk/frontline/rearsus.htm

https://www.petermayengineering.co.uk/

My car has a 3.9 final drive but I've heard that the 3.7 was fitted to the very last cars (mine's a '78). I'm using the stock "open" diff, by the way.

 

[Matthew E. Herd]

I can verify that, indeed, according to Jim Knight of British Racing Green, only the last few thousand cars had a 3.73 differential. Also, apparently all axles are interchangeable. I had some confusion about that, but don't know where I got the idea that they weren't the same. As of yet, I have not been able to get to the bottom of the problem, but I suspect it's an axle shaft or spider gears. I'll update as soon as I know. However, if the ring and pinion need to be replaced, how does one go about rebuilding the differential? It would seem to me that the backlash would need to be set with shims, but I wonder what the specification is. I also wonder if there are any other settings that are critical. Can anyone speak to this? Thanks!

Also, an update from what I've read on the Grassroots Motorsports page concerning the Phantom Grip differential. It would seem that it is essentially the stock differential spider gears and carrier, with a spring loaded metal block that presses against the spider gears to slightly prevent rotation. However, the resistance is not all that great (depends on spring rate), puts large additional loads in unintended directions on the spider gears and shaft, generates metal swarf that can be very bad for bearings etc as the block and gears wear down, and finally, once the wheels start spinning at a different speed, they're inclined to spin almost as with an open differential due to 'stick-slip' friction where static is greater than kinetic friction (the whole reason behind ABS). Therefore, it will not appreciably help power you out of corners like a genuine LSD, regardless of design (other than this one). A welded diff is definitely harder to drive on the street, but at speed, it would likely provide considerably better performance than an open or phantom grip setup. Basically, it would seem that it isn't worth it unless you like rebuilding your differential. As an aside, I don't personally own one of these units, so I only can go by what other people have said and by the diagrams on their website. I am only drawing conclusions based on hearsay, not the actual design. However, these conclusions are negative. It would be great if this unit worked, as it's quite cheap. Unfortunately it does not appear to do what they claim very well. Also, there are reports of exploding differentials as a result of this item, which is logical as you are stressing the already comparatively weak spider gears of the differential even more. Ask Mark (SilentUnicorn) about what happens when you drop the clutch at high RPM ... the gears will self destruct. This unit will probably induce failure even more easily, so I'm not inclined to try it. Hope this helps for future reference.

Matt

 

[Matthew E. Herd]

Update on my situation!

My father graciously jacked up my rear wheels and spun them. Amazingly, they spun in opposite directions just like they're supposed to. However, the fact that the car was in gear seemed to matter little, as the driveshaft rotated regardless of gear selection. So, this afternoon, he tried all the gears with the engine off and found nothing in particular. Then he tried to run the engine and select gears (the wheels were still unloaded). It did nothing in second, nothing in third (I was in second when the "CLUNK" happened). Then he went back to second, and apparently it made another amazingly loud clunk and the wheels spun a little. However, he then chose to shut it down. Any help with what this might be? I'm most likely going to pull the engine and clean up my spare used transmission, hoping it works A-OK without a rebuild, and install it for now. However, I hope to rebuild this one again and put it in at some later date. Any advice is appreciated, as I'm unsure what the problem could be. From my understanding of transmissions, since the dog teeth were already engaged because the car never left second during the whole clutching and subsequent banging, the synchros can not be destroyed. That leaves the gears themselves, which may be trashed.

Matt

P.S. On the upside, I won 1st in my class at our autocross club's event today! I beat out a friend with a 2000 Ford Crown Victoria with a Police Interceptor package and a limited slip with my 1985 BMW 325e! He's got about 90 HP, a limited slip, a marginally stiffer suspension, and about 1200 lbs on me, but we're amazingly well matched /ubbthreads/images/graemlins/smile.gif The fact that I beat him on my last run was really exciting, esp. since I dropped over 1.5 seconds on that run and we were neck and neck before that!

 

[aeronca65t]

Don't pull the engine until you check the axles...sometimes they will lock/unlock at the broken point (making a clunking sound).
Not that these gearboxes are unbreakable. I have seen one of these 1500 transmissions blow up (in a Spitfire)...it did so much internal damage, the case was cracked.
Congrats on the Auto-X.

 

[Matthew E. Herd]

Finally, I have the trans out and detached from the engine ... only two days work, not too shabby. Incidently, I found that the forward U-Joint was busted, so I got the parts on Saturday. However, I decided to try to run the engine and shift through the gears to make sure the transmission was ok. It was not. I just finished pulling the engine tonight, as well as pulling the top cover on the trans. To my dismay (although it is pretty interesting), the teeth on the input shaft and the teeth on the matching gear on the layshaft are blown off in one or two spots, with absolutely nothing left but stubs. I have a well used spare to swap, but it would seem that the laygear and input shafts are both unavailable through moss. Does this happen much on 1500 boxes? If so, it could prove a serious problem.

Matt