Ramifications of swapping out rear ends - personal experience and advice :)-D

I thought it might be useful to post my experience with installing a different rear end than stock so others know what they are in for in terms of both modifications required and associated costs.

I have a Ford 7.5" rear end with drum brakes that was built by someone local. The rear end, plus new axles (not shortened ones), plus new emergency brake lines cost me about $1,400 but that was just the beginning...

First word of advice: verify the axle width you need based on your tire width and body flares. If you are getting it built like I did, and as long as you are positive about your measurements, trust your instincts in terms of width, even if the builder tries to talk you out of it. I didn't follow my instincts and now I have to use a 3/4" spacer on the passenger side. I am currently getting a spacer machined so that will probably cost anywhere from $20-$50.

Second word of advice: make sure the builder understands implicitly your needs. For example, I requested that the builder use my almost new wheel studs (ARP studs with <500 miles on them) on the new axle because they had the thread pattern that fit my lug nuts. Unfortunately the builder decided to install new ones with a different thread pattern without asking me so I had to get the axle hubs re-drilled for the studs I wanted. That cost me an additional $150 in machine shop costs.

Third word of advice: Installing a new rear end has many ramifications that I wasn't aware of.
1. For mine, the spring perches and u-bolts did not fit my new axle because the axle tubes were much larger than the original ones. I had to do some modifications to make them fit. No costs associated but it was a bit of a PITA to make everything fit.

2. The new axle diff is larger in diameter than the original and this caused issues with fitting the rear sway bar. The person who assembled the axle provided spacers for the sway bar but there were two issues with using spacers: 1) the sway bar would contact my fuel lines with the spacers installed, and 2) I suspect that having the sway bar at a different angle would affect handling (I can't confirm this). In the end I decided to not install my rear sway bar because I didn't want to re-route my fuel lines.

3. I had a nice driveshaft made by Brian M. at BMC for my original T5 to stock rear axle. The new axle not only required a new driveshaft yolk to be welded on, but also required that the tube length be increased by 3/4". This cost me $275.

4. The stock emergency cable setup didn't work with my new axle. I had to modify the MG brake cable and also modify the Ford emergency brake cables, plus make brackets so that everything would work together. This was just a time thing but it ended up taking me a couple of nights to do.

5. This may just be a brake setup issue that can be solved by adjusting the rear drums but my pedal goes much closer to the floor than before, which suggests that I might need a larger brake master cylinder for the new rear end. However, I have also done the Jeff Schlemmer brake pedal box modification (lowering the height of the master cylinder for more brake pressure with less effort) so it may be a combination of the two. If I need a larger master cylinder I am probably looking at around $100 for one (us Canadians get the shaft on car parts!).

That's all I can think of for now. Total cost to date for a DRUM brake setup is just over $1,800 not including a new brake M/C if I need one. Would I do it again? Yes, but I would approach it very differently!

Cheers,
Chris



I didn't think about these things when I started the conversion process.

wasn't your "builder" responsible for the 150 bucks in #2?

I'm kind of curious what the builder charged you for the narrowing and what other work he did for you. It all seems pretty high compared to what Moser charged me for the work on my 8.8. I had about $450 (no shipping, so that would have to factor in) for the narrowing and two new axles. I definitely had anxiety over what exact width to make mine, as there isn't a lot of extra room in the rear wheel housings and it pretty much needs to be perfect. At the last second I kind of wanted to make it about 3/8" narrower on each side with the thought that I could always use a spacer, but you can't make it narrower. Mine is barely narrow enough and depending on the tires I use will probably require a panhard to not rub.

Bryan, that would have been nice but no. I don't feel like having an official disagreement over it especially because the British car community up here is small so I'm over it.

Ryan, yes it was expensive but that was my only option up here since shipping an axle from the US would have killed me. I decided to have someone else do it because I had enough on my plate and thought it would simplify things. In hindsight I should have probably done it myself because I am a super anal person!

Like I said, the reason for the post was to try to highlight the costs and challenges I ran into during the conversion for others thinking of going down this path. I wish I had this information before I started but hindsight is 20/20 as they say! >:D<

Chris, you have my sympathy for all the problems you've experienced. As for the brake problem, try installing a residual pressure check valve in the rear brake line. A 10psi model should work fine and really reduce your pedal travel to a comfortable level. (Wilwood) I read your other thread on the spacer issue, that's the way to go for now if you want to get it on the road soon, but recentering the housing by moving the spring perches would be what I recommend in the long run. I'm surprised that you're having to have a spacer machined, there are usually spacers available off the shelf that would fit most performance rear axle flanges even in a 4 lug pattern. I picked up spacers I use on my Midget at the local auto parts store. As you know by now, a little pre planning and checking can save you a bunch of money. I'm a real cheap sort and always build my cars on a budget. When I did the rear for the Midget I checked and found that the Chevy Monza had the same lug pattern, no machining of the axle flanges or brake drums. It also had enough steel in the axle shaft at the point where it needed to be resplined that I didn't have to buy new axles or have mine welded up, again bucks saved.
As you found, doing some reasearch on the different housings available can save you time and money.

Thanks Bill! Good points as usual.

My problems are small and to be expected when you modify a car. Changing one thing usually impacts one or more other things on the car. I guess I'm at a stage now where I just want to drive it for a bit!

As for the residual brake pressure valve, I'm not sure if the brake sponginess issue is because I lowered the master cylinder height or the Ford Ranger brakes. The drums are about the same size as the stock MG but maybe the brake cylinders are bigger requiring more brake fluid (I didn't measure them)? First I am going to get the rears properly adjusted. Then I'll decide what route to go. I have the stock brake pedal housing so I can always go back to it.

That's the problem with changing more than one component at a time. You don't know what part to blame for a change in something!

Cheers,
Chris

Admittedly I did mine 8 years ago but I bought a ready GM rear axle with pozi and 3,08 ratio from D & D and it was literally a bolt in at 2 hours work and well below that cost, maybe a bit more today but sure saves alot of work and frustration---my 2 c worth

As they say Gil, hindsight is 20/20. My installation has taken many nights of work so far so I am very jealous of your situation!

I hope my post helps others who are heading down this path minimize mistakes and cost during the conversion.

All of your issues can be fix.
There is one that I do not understand. You are saying "I didn't follow my instincts and now I have to use a 3/4" spacer on the passenger side. I am currently getting a spacer machined so that will probably cost anywhere from $20-$50.

What about the other side?

You're right Bill and I have addressed them all except for the brake sponginess and that is probably due to a couple of things that I am working out.

The driver's side wheel spacing is fine requiring only a small spacer to get it where I want the wheel. It's the passenger side that needs the big spacer. I can even things out to a certain degree by doing what Jim suggested and shifting the axle over but for now I'm taking the easy route.

Chris,

I did the Ford 7.5 too. Sorry you have had some issues sorting it out. For the brakes, mine worked just fine, no changes to the master cylinder required. I did replace the wheel cylinders and I made new brake lines. I thought my brakes worked better after the rear diff conversion. Just my $.02 worth.

Brad

Interesting, thanks Brad! I have new brake cylinders and brake lines on mine.

I expect I need to adjust the rear brakes (not done yet) and possibly switch back to my original brake pedal box. I get the driveshaft back in another week or so then I can fire it up again and see if all my work over the past few months has sorted out the various bugs. Then I want to drive the damn thing!!

Chris

Chris,

You can't seem to catch a break on this project of yours.

Refresh my memory; what advantage will you have with this new axle over a stock unit? What are our plans with this car?

I'm just curious. Not saying what you're doing seems extravagant as I'm sure you're learning plenty. What was wrong with putting some miles on the car this summer and then modify it?

Modify!!! :)

The previous gearing was not fun with first gear pretty much useless and the engine revving fairly high in fifth at highway speeds. So I needed taller gears and since I had the "one tire fire" syndrome it was "might as well get a LSD while I'm at it".

I'm fine with overcomming the various hurdles but it would have been nice to know what I was up against before diving in. I know it will be worth it in the end so I'm not really worried.

Chris the rear wheel cylinders size could be the culprit. Once you adjust the rear brakes then check for the size of the wheel cylinders.
Your axle guy should align the axle for you. To bad you are so far, I could lend you a hand.

Once the rear brakes are adjusted, they should adjust themselves.
Do not want to ask the following, but you need to know. Ask if the self adjusting mechanism was installed in the rear brakes.

The axle can be center by....see picture.

Chris,

I am certainly not the expert on this forum, but as I have run into hurdles with my conversion, I remind myself: This is a conversion! We are putting engines, exhaust systems, suspensions, transmissions, differentials, wiring, etc., in a car that was designed for something else! That means, learn to expect the unexpected! I don't know if this might help you, but I must remind myself of this with everything I do with my car. Good luck with everything, keep us posted and asking questions!

Brad

"Modify"......Ahh, yes, I remember now. ;)

I believe we talked about swapping diff gears like I did and IIRC, you figured if you had to spend that kind of money, go for the LSD.

It's all coming back to me now. :)

You'll have all these mods sorted out by Gary's Run, correct?

I'll have everything sorted in March for sure. I found my coolant leak sites (brackets weren't tightened down enoug). Next is picking up my new driveshaft so I can add tranny oil. Then I can start the car and use my fancy new rover engine analyzer thingy to try to track down my mild miss when the engine isn't under load...

I saw someone mentioned a GM diff from D&D, is that a good option and how much does it cost? Aslo, does anyone have any experience with Fast Cars Inc's 8" Ford rear end, and know how much they run, cost wise?

I'm all for buying one that's already been cut to fit and such, not wanting to do my own, I like welding, but not that much.

Nice write-up Chris.

If your brakes feel a little soft, have the rear wheel cylinders sleeved down to the MG rear wheel cylinder size if your leaving stock front brakes and master cylinder. Most of the time, Domestic brakes have too much volume back there and do not allow for the limited fluid we have provided by the MGB master cylinder. This is what we did with an 8" Ford rear end in a Sunbeam Alpine V6 Conversion and it worked very well after this.

-BMC.

Brian is right on wheel cylinder size. The Ranger had two brake drum sizes. 9" and 10". I imagine the 9" had smaller wheel cylinders. So if you have the 10" use the 9" wheel cylinder.

Good suggestions guys! I'll give that some thought when I get home (in Hawaii right now)...

Have you got nothing better to do in Hawaii than spend time on here? :)

No I don't. I'm herre for a conference. Been there, done that....

>:D<

Chris,

I can sympathize with your experiences. Without hijacking your thread, been there, done that and still trying to figure out a few issues.

RE: Long brake pedal. Wheel cylinders. My rear had 5/16 bore cylinders should be 3/8.
The correct cylinders should be Napa p/n's 17508 /17507. It took quite some time to trace down the proper bore but luckily my local guy had patience and took up the challenge. The brake pedal feel along with the braking performance improved significantly.

(PS: Before changing the WC I installed both a proprortioning valve and residual pressure valve with little affect)

PSS: Please PM me If anyone can recomend an East Coat guy who has what it takes to check the housing alignment of an 8". Curry Enterprises in CA is all I know of. Moser won't work on my 8".

Chris, Also on Jeff's pedal box mod he went with a size smaller master with stock front brakes. Put your old pedal box back on until you go to larger front brakes.

D&D is an excellent choice for a differential. For price is best to call them and ask Marc.

What about Fast Cars Inc and their 8" Ford diff, is it any good or is the D&D one better?

D&D doesn't work on the Ford 8".

I spoke with them yesterday.

Yes, that makes a very good choice, one of the best. Strong but not heavy. Just to cloud the issue though, the Ford 8 and 9" gear sets are slightly less efficient than a higher pinion set like the Dana or Salisbury. It isn't much, just a couple of percentage points and in practice I doubt you could tell the difference, and it is outweighed by the lightness anyway for most applications. But if mileage is your bag it might be one of those things you'd want to optimize, and that partly explains Ford's move to the non-removable housing after so many years. It was one of the factors I considered when designing my IRS that led to the use of the Dana 44. In the end, whether you have the 8", the GM 10 bolt, the Dana 44, the Chrysler or some other axle there will be at least one factor you can point to and say it's the best.

But the bottom line is that axle choice will always be a compromise, and balancing out all of the different factors is what it's all about. There is no one perfect choice.

Jim

Jim I agree about the gearing, I've looked into that, luckily this is a project car and fuel efficency is about #1005 on the priority list, and I actually quite favor the Ford 8"'s 3.25 :1 set, with the Ford Racing T5 gears it is pretty even with a corvette's speed ranges, and my power to weight should be better, so project KillVette should be a GO!! :devil:

I did the Ford 7.5 into my Midget. It wasn't bad. I got the axles done by Mosier Engineering. I also had the drive-shaft and u-bolts made before I began the dis-assembly. I used the '99 Mustang rear end and Honda Civic rear rotors. I also bought new spring pads from Summit so I did not have to cut up the old axle at all. I love my 2:73's and the Ford LSD.

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