BritishV8 Forum

One of those things I'd never done before. Installed a few but never narrowed one myself. Actually, other than the constant second guessing on the math it wasn't bad at all. Rather than re-post the whole story here, you can catch the complete blow-by-blow at my Tempus Fugit Garage site (personal playground): http://tempusfugitgarage.com/narrowing-ford-88-differential/

The gist is, I needed to get a rear end up under my conversion project and was able to land a nice 8.8 with a Trac-Loc on my doorstep for $250. After looking into the cost of having it done or buying one, I decided to give narrowing it myself a go. While I don't think there's all that much savings to be had after I add the brake package and the axles from Moser, I'm still glad I did it. Wouldn't call it fun, but something I've wanted to do.

Just for comparison sake, I was able to source a narrowed 8.8 for about $1500 complete with rear discs, not including freight. By the time I include the spring perches ($50), the differential itself ($250), the axle/bearing package ($500), the disc brake package ($400), the axle housing ends ($100), the paint, wheel seals, welding rod, and other sundry items, I have around $1300 in the project. Not a ton of savings especially if you want to include the time but enough to keep me in beer for a little while.

I'm also going to post this over in the Projects section just to keep the journal up to date but thought it might be of interest to those folks who don't wander over there.

Word at "Speedtalk" is the 8.8" is lighter, and less drag than a 9".  An 8" wouldn't cut it ? Good Job, roverman.

Art,

An 8" probably would have been just fine but this one just sort of ended up in my lap for a very small ($250, including freight) cost and it's a rear end I'm very familiar with making suppliers and sources for parts easy. So this was more a 'crime' of opportunity than the product of careful planning. That said, the 8.8 is a good match for the dry sump 302 and the WC T-5 that's behind it. Will also make sourcing the driveshaft simple.

DT

The 8.8 has a better pinion angle than the 8 or 9" so it has less drag. (The pinion is closer to the centerline, more like the Dana and GM diffs)
This means better economy and less heat. The difference isn't much but it does help a little.

Jim

Good to know Jim. I never really thought about the nuances of my choice. It keeps sounding better all the time.

It's  a balance of compromises. The 8.8 is heavier so there is more unsprung weight but it is strong and available, and pretty well bulletproof.

Jim

True enough Jim. I did my best to reduce some of the weight by getting rid of anything that wouldn't be used - brackets, etc. + I lost a little from the nearly 10" I lopped off the tubes. Still, the 8.8 isn't going to win any contest in the svelte department. As far as durability goes, I had one behind a 425hp monster and it held together despite some admittedly hard use (okay, abuse). The T-5 and the clutch gave out, but 8.8...never.

JB, The 8" ford has more pinion drop than the 8.8"?  9" ford pulls about 5hp more drag than similar ratio 12 bolt GM,(Car Craft test). I personally like a drop out center section for ease of service, especially on a vehicle that may need a ratio change,(different forms of speed challenge). roverman.

The 8 and 9" are the best for gear changes and for light weight, but if you look at the gears themselves it is clear that they have a higher helix angle which is also the reason they use a bearing on the end of the pinion. Tha helix angle determines the amount of parasitic loss. Straight cut gears would be the most efficient but you would not enjoy the drive.

Jim

Most of this info is over on MGE but, for those who don't get over there, before installing the narrowed rear, I decided to have one more measurement and, after checking the runout. Was really bummed to find out that that the new housing ends were out of square by enough that I was skeptical about installing the new axles.

Enter Mssrs. Stabe and Blackwood who suggest strategically heating and quenching the axle tubes to bring things back into square.Frankly, I was a bit skeptical but game for a try. Amazing! You could actually see the damn thing move!  

End result? The runout to the front is 1/16" narrower at 24" from center than the rear. The top-to-bottom difference is 1/32" (the bottom being slightly wider).

It took some experimentation but eventually I got the hang of it. Way cool! You just have to try this. Find an excuse. It's that neat to see.

As I might have said in a previous post, the new Moser axles are significantly beefier than stock. Everything went together without a hitch. The only question I have is the fit of the bearing and the retainer (this is my first c-clip eliminator 8., something I'm going to ask the Moser folks on Monday. I'm having trouble posting images here so, for more details on feel free to visit: http://tempusfugitgarage.com/narrowing-ford-88-differential/

Meanwhile, back at your garage, you mention possibly/purposely changing toe and chamber on a live axle rear end. How is this possible without relocating the opposite ends of the axles ? With ball splines on full floating axles, this readilly accomplished. Seems to me, welding the ends on crooked, will mostly affect how bearing and retainer seats and bolts up. Tire/wheel alignment and drum/rotor wear patterns, should be minimally affected, because the axle shaft alignment determines these. A bent axle housing will more likely affect wheel alignment, up to and including binding on the axle splines.  Nice work.  roverman.

"you mention possibly/purposely changing toe and chamber on a live axle rear end. How is this possible without relocating the opposite ends of the axles ?"

Following Jim Stabe's and Jim Blackwood's guidance, I think the gist of it is, if the axle housing ends are square in both the vertical and horizontal planes to the tubes and the tubes are square to the pumpkin then heating and quenching the tubes (nearest to the housing ends) "shrinks" that dimension, effectively adding either toe-in or camber or both.

I'm sure either Jim can explain this more accurately than I can but, what I can tell you is, after applying the heat and quench method to the tubes, the housing ends are now as square to the tubes as my skills can make them and, the new axles went right in with a small tap on each to seat each. I'm a happy guy.

Quick update on the bearing retainer fitment. Talked with the folks at Moser this morning (I should probably just add them to my quick dial function) and was told that the bearing is supposed to fit proud of the housing and to tighten the retainer plates until they have a slight bow in them and call it good. Done.

While I had them, I also asked about the run out on my housing ends and was told that the typical Ford factory tolerance for the 8.8 was as much as 1/2" or greater. Wow! Makes me feel pretty damn good about how close I was able to get things with the advice of Jim Stabe and Blackwood. Thanks again, guys.

Differential is up and under the car but not bolted down (waiting on spacers to arrive, will also post some pics once everything is nailed down). I did notice that I'm going to need to either cut the "ear" of the right side of the pumpkin (originally used to mount the factory counter weight) or move the battery into to the trunk and cut off the old box. Once the differential is in its final position, looks like, under compression, it's going to hit the edge of the stock battery box.

Fortunately, I have all the coming winter to solve the problem, along with re-assembly and a whole host of other things that need to be completed.

David, Axle looks good! Doesn't the rear disc bracket go under the retainer? Also most guys run a bead of weld where axle tube goes into housing as they are known to spin.

"Doesn't the rear disc bracket go under the retainer?"

Darn good question which I am unable to answer until the rear brake kit arrives, hopefully sometime next week. Until then, I'm just going to bolt the rear wheels on so I can roll it out to the paint shop on the 31st.

Unusual for the 8.8s I've had, this one has two plug welds (typically I see just one) at the tubes so I elected to leave it as it is. The end housings have been perimeter welded. Sure would be ugly if an axle tube spun.

Here are a couple of shots of the car actually sitting on it's own four wheels and suspension. Sorry for the skanky looking body, am in the process of block sanding it in prep for paint on Friday. Happy to report that the rear end fit right under the car and bolted in without incident. Track width is spot on.

Car is sitting a little higher than I'd like but maybe the suspension will 'settle' a bit. In any case, once it comes back from paint, I'll have all winter to dial things in.

Love those wheels!

"Love those wheels!"

Thanks Carl. Story is, I found them chained to a tree along one of the routes I take to my office. Had been there for at least two years when I finally stopped in to find out what the deal was. Turns out they're 16 x 7 BBS wheels from the early 70s that came on a Mustang the owner had bought. He'd been trying to sell them for quite some time when I happened along. I asked what he wanted for them and he said, "$150 including the tires." Initially I thought he meant each, which would have been an okay but not spectacular find, but he meant for the set. I paid him on the spot and loaded them into my car before he changed his mind. I still feel the guilt...

I've been dreaming about BBS RS like those for years.  Did you happen to weigh them without tires?

"I've been dreaming about BBS RS like those for years. Did you happen to weigh them without tires?"

Carl,

Haven't weighed them yet as I left the old Dunlops (hard as rocks) on so I can roll the sled around the garage when I need to. When I swap tries in the spring, I'll weigh them and see what they come in at (already made a note on my MGB "to do" list for you). I'm also curious as to what they weigh but judging from how easy the tire/wheel combination is to heft up and on the hubs, not much.

DT

Quote from Art Gertz
Meanwhile, back at your garage, you mention possibly/purposely changing toe and chamber on a live axle rear end. How is this possible without relocating the opposite ends of the axles ? With ball splines on full floating axles, this readilly accomplished. Seems to me, welding the ends on crooked, will mostly affect how bearing and retainer seats and bolts up. Tire/wheel alignment and drum/rotor wear patterns, should be minimally affected, because the axle shaft alignment determines these. A bent axle housing will more likely affect wheel alignment, up to and including binding on the axle splines. Nice work. roverman.


Art

You are correct. All I was trying to do (and Jim B as well) was to get the outer bearings to run without binding and to not apply bending stress to the axle. What the circle track guys do is to bend the housing up next to the pumpkin to give a slight camber at the wheel similar to what a swing axle VW looks like if you push down on the car in back. The axle splines aren't happy running at an angle so they generate heat and wear out quickly, not something you want to do with a daily driver.

I wonder if ball spline configuration is available for semi-floating axles ?  Seems to me, the carrier will need to  be offset downward, as the ends of the axles will, during decambering, to get negative camber without the binding.  Cheers, roverman.

"I've been dreaming about BBS RS like those for years. Did you happen to weigh them without tires?"

Carl/Floyd,

I just had the front tires swapped and, while I was at it, took the opportunity to weigh one of the rims - 14.7 lbs without the knock-off and center ring. Also just found another pair on e-Bay that I'm going to pick up as spares.

They're damn hard to find in 16 x 7. Tons of 15s out there taken off, it seems, every Firebird that ever lived but the 16s are very scarce and when do find a set, they want an arm and a leg for them. Who knew? Back in the late 60s, early 70s when these were popular, I bet every other kid in my high school had them on their car.

DT