differential conversion from 7.5" to 8.8"

[MTCFORUM]

another thing I'll add is that if you plan on upgrading your engine, or adding power you need to consider replacing that weak 7.5" differential. If you want to regear your V6, now's the time to do this

Before I had any serious mods I managed to break mine, causing the differentail cover to twist right off the mount, and then damage one of my halfshafts.

You can easily replace that 7.5" differential. All you need is one from a V8, SC, or Mark VIII. Get the half-shafts while you are at it, the larger ones are much better. And if you have a parts car, also get the spindles, calipers, rotors, brake lines, and e-brake line. If you score all those goodies (you should find them for under $400 at a junkyard) then you can have the stronger parts AND rear disc brakes.

Brian

[MTCFORUM]

This is on my list. I'm afraid between the J-mod and the CustomChip (if I ever get it installed <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emsmilep.gif" BORDER="0">) that the 7.5 might go south. So much to do, so little cash!

Joe

[MTCFORUM]

personal experiance!
Jmod+Jchip= Blown 7.5" after 2500miles, the Spider/side gears EXPLODED on a 1/2 shift while away from home. Had to weld them toghether(as in both wheels turned the same speed at all times) to make it home.

[MTCFORUM]

Yep, I done somthing similar back in 99.

I was spinning off the line, and one side hooked up. The halfshaft snapped, and twisted the Differential right off by the back mounting cover.

The half shafts are pretty weak, so by far the best deal is to get the whole rear assembly out of a SC or V8 and swap it ALL in. My swap cost about $400 including new CV boots and bearings.

Brian

[MTCFORUM]

I have been running a 7.5" diff in my SVOs for a couple years now. I am dedicated keeping the 7.5" diff for authentic reasons but I have had to watch them carefully. They do loosen up, especially the side play and have to be reshimmed yearly. The SVO has about 200+hp but not much torque under 3000 rpm, which is a bit of a saving grace on the diff. Little shock load and the power and torque comes on gradually.

If you are running a 7.5" diff, check it often for side and pinion play. Replace the crush collar with a solid spacer and shims. Use a high quality (synth) lube in the recommended weight (not thicker!). Locktite and torque all bolts. Watch the spider pin wear and either don't spin it or keep the tracklok up so the spider gears don't burn to the pin.

Better yet, get the 8.8" diff!


Steve Best
SVO: <A HREF="http://sbest4.tripod.com" TARGET="_blank">http://sbest4.tripod.com</a>/
SC 5spd: <A HREF="http://stevebest1.tripod.com" TARGET="_blank">http://stevebest1.tripod.com</a>/
4x4van: <A HREF="http://www.glinx.com/~sbest" TARGET="_blank">http://www.glinx.com/~sbest</a>/

[MTCFORUM]

<BLOCKQUOTE>quote:<HR> Better yet, get the 8.8" diff!<HR></BLOCKQUOTE>

I'll be doing this swap sometime this Summer. Seabass gave me a good link on doing the swap. I'll need to go over it a few times and make sure I have everything I need. Is it a good idea to go with new driveshaft bolts when doing the swap? I'll change out the IRS bushings and tranny mount while I'm at it. Also give the driveshaft the once over too. <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emsmilep.gif" BORDER="0">

Joe

[MTCFORUM]

Joe
I used my stock driveshaft bolts with my new differential, cleaned the bolts up then slapped some lock tight on them, they were fine. Of course I only have 24000km on my bird, not much stress on many of my car's bolts yet <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emsmile.gif" BORDER="0"> If you have quite a few km on your car I would say it would not hurt to change the bolts out with some new ones just to be safe. I could be wrong but I have not heard it recommend that they be changed with the diff. swap.

I have heard of some nasty stories of people who did change the driveshaft / differential companion flange bolts and were unable to get the new ones to stay tight (of course this may have been simply because they were not using the correct replacement bolts, or not using lock tight aka could have been people slightly challenged lol). This however has not been my expereince. Anyway after I did my diiferential swap those stories made me a bit paranoid about my own stock driveshaft bolts and I was checking them quite regularly (they have been solid / fine since I installed them). I do not anticipate them coming loose ever again until I install a new driveshaft <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emwink.gif" BORDER="0">

[MTCFORUM]

When I did the conversion I didn't replace the bolts, and to my knowledge the car is still around and using those bolts <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emsmile.gif" BORDER="0">

It might be a good idea to change them, but I was probably just too lazy. That and all of the bolts/threads looked good.

[MTCFORUM]

Eric,

Mine has 50K miles on them (not sure what that adds up to in km), it's late! I thought I heard it was a good idea though to change them, just wanted to be sure. Thanks for the response, what are you using for a driveshaft now?

Joe

[MTCFORUM]

Joe
I am using my stock driveshaft currently. I briefly talked to Dennis about the possibility of getting a metal matrix composite driveshaft from him for my car, and he said he would be able to hook me up. The price is costly but will be worth it for the quality. I anticipate my high speed vibration issues will be cleared up (not that they were really that bad to begin with). I will also have peice of mind regarding critical driveshaft speed, plus I am sure the car will see some very slight performance improvement. I have to call Dennis back and find out how he wants me to measure my stock driveshaft (from what to what), which should not be fun since it is conveniently underneath the gas tank. <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emsad.gif" BORDER="0"> I may just call my local ford parts person and see if they have some spec.s on my stock driveshaft length (wouldn't that be nice if they did).

If your stock drive shaft / half shafts have any issues they will definitely be made apparent after the diff. conversion.

[MTCFORUM]

<BLOCKQUOTE>quote:<HR>
The half shafts are pretty weak, so by far the best deal is to get the whole rear assembly out of a SC or V8 and swap it ALL in. My swap cost about $400 including new CV boots and bearings.
<HR></BLOCKQUOTE>

Brian,
I might be picking up some axles out of a SC parts car. So will I be able to use these axles and just have the CV joints replaced? If I'm doing the rear end, may as well go all the way! <IMG NAME="icon" SRC="http://images.zeroforum.com/smile/emwink.gif" BORDER="0">

Joe