A question for those who drove the GRM crapcan Mark VII.

After the spider gears were welded how did it feel going around slow speed, tight turns?

Was it a toss up between understeer and oversteer?

Any shuddering?

I'm considering a spool or welded rear diff on mine and am curious how the Mark VII platform responded. I've been advised not to do it by some people and others have said it would be just fine.

I've driven a welded diff car (well, boat) on track quite a bit. In the dry it's not even noticeable except you had a ton more traction. In the wet it's a lot more tail happy. But driving around the pits and especially with a bunch of people in it, it does not like to turn and there's a lot of jumping and shuddering. If you're going to drive this on the street a lot and have to park it I think a welded diff would be a pain. But on the track it's brilliant.

If this car is trailered to a dirt track, sure, why not. Anything else, I wouldn't even consider it. Shuddering around corners, breaking parts, etc.

We have loads of track time on the boat and the rear end hasn't given us any trouble. We're way faster around the track with the welded rear end - without it we were doing the one wheel peel around every corner. It's got maybe five races on it, around 15-16 hours each race.

The couple guys I knew that ran welded spiders or spools, things broke, like axles shafts. I just couldn't see doing it to a street car with an 8.8 rear when factory posi units are so cheap and there's lot of other options out there.

I know nothing, but I have to assume that the stickiness of your tires is going to have a big impact on how the welded/spool diff behaves in tight corners. Maybe this is the difference between the success and failure outlined above...

pres589 wrote: If this car is trailered to a dirt track, sure, why not. Anything else, I wouldn't even consider it. Shuddering around corners, breaking parts, etc.

^This. (Edit: Would also do it on a dedicated drift car)

pres589 wrote: The could guys I knew that ran welded spiders or spools, things broke, like axles shafts. I just couldn't see doing it to a street car with an 8.8 rear when factory posi units are so cheap and there's lot of other options out there.

Definitely don't do it on a street car. Even "tight" turns on a track are not actually that tight compared to city driving. I just meant for asphalt road-course track use it's not a bad thing. I don't know what his plan for the Mark is.

In reply to dculberson:

Yeah, I think this means street, since he's trying to keep the car nice and I don't think he's mentioned a cage or other racer stuff.

I wonder about going around a street corner with a welded diff in a Fox-body Ford like his; the shuddering coupled with the entirely awesome rear suspension and torque boxes that like to rip if the car is treated badly could make for an interesting way to destroy things.

I have the Scoob and the Burban for DD duties so I'm not really concerned with civility...that much. It'll be a novelty to drive on the street! I was more worried about unpredictable handling, i.e. transitioning from understeer to oversteer and back again with little to no driver input. Or plowing understeer in tight, slow speed turns. It's looking like the car might make it to a few Solo2 events but as of now, no RallyCrosses are even on the radar.

I'd assume others have broken parts for the same reason peter outlined; sticky tires. I'm not willing to pony up the cash for an actual diff., the same can be said for new, sticky tires. I'll be using used tires, most likely all season or truck tires at that. This is the Stincoln after all.

Ooh, I hadn't thought about the torque boxes ripping out.

In reply to pres589:

Nice is definitely relative! And you're right; no cage. I plan to keep a full interior though I will eliminate the smog equipment and I may eliminate the A/C.

My big objection to a welded rear is the turn-in characteristics. It requires trail braking into a corner to avoid major initial understeer. I once had a big wreck in my ITA car when I tried to take a chicane flat. I turned in, but it didn't - plowed straight off into a tire wall at about 80 mph. That hurt.

I am interested about this because all of my experience with spools and the like was in the drag racing world, where some cars literally could not be pushed by hand around a corner because of tire traction.

For Lemons, it sounds like something we should be doing.

The_Jed wrote: I have the Scoob and the Burban for DD duties so I'm not really concerned with civility...that much. It'll be a novelty to drive on the street! I was more worried about unpredictable handling, i.e. transitioning from understeer to oversteer and back again with little to no driver input. Or plowing understeer in tight, slow speed turns. It's looking like the car might make it to a few Solo2 events but as of now, no RallyCrosses are even on the radar. I'd assume others have broken parts for the same reason peter outlined; sticky tires. I'm not willing to pony up the cash for an actual diff., the same can be said for new, sticky tires. I'll be using used tires, most likely all season or truck tires at that. This is the Stincoln after all.

Is SOLO2 autocross? I would not weld a diff on an autocross car.

Yeah, sorry.

More often than not I refer to it as Solo2.

In reply to The_Jed:

Ah, then I would say "no" to the welded diff. It's not going to work well for really tight, twisty corners.

It was terrible–horrible understeer with snap oversteer. I would never recommend it, and our less-experienced drivers could barely even keep the car on track. Trail-braking helped very little.

Add more clutches to your traction lok.

In reply to Gasoline:

According to the diff tag mine was a peg leg from the factory...of course, it's supposed to have 3.27 gears instead of 3.73 gears too...

I think I'd try to figure out what the spline count on your axles are and go looking for a matching traction-lok diff. Should be pretty cheap.

In reply to pres589:

All of the info I've been able to dig up points to 28 splines. I'm not going to pull the trigger on a diff or anything like that until I verify the spline count.

if i remember right all of Andy Nelson's challenge creations have used a spooled rear axle, including the years he placed right near the top of the autox pack. and the Jeep XJ-R's LSD got stuffed as tight as reassemblable and feels great for what that's anecdotally worth anyway

Tom Suddard wrote: It was terrible–horrible understeer with snap oversteer. I would never recommend it, and our less-experienced drivers could barely even keep the car on track. Trail-braking helped very little.

So 'no-go' on the welded diff from the only guy here who drove it, yeah?

Correct. At least for our heavy car with soft, squishy springs.