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Author Topic: Does my rear end look too big?  (Read 1045 times)

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Offline 76hotrodpinto

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Does my rear end look too big?
« on: September 06, 2015, 12:32:24 AM »
After much head thinkin and stuff, I've decided to replace my 8" m2 rear end with an 8.8. I found a guy to chop it down to size for me, but I am trying find the perfect length for it. I want to get some 15" wheels and some beefy tires up in there, no tubbing. If I can avoid having to use a custom offset backspaced wheel, by getting this just right, it's worth trying. I'm considering the mono leafs as well... if my ocd will calm down about the 4-link. Ugh. So have any of you cut down an 8.8? If so, what length did you go with? Would you go a little bigger or smaller, if you had it to do over?

Please don't post any pics of your 4-link systems, especially the untubbed cars...ahem.
1976 half hatch 2.3 turbo w/t5.

Offline russosborne

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Re: Does my rear end look too big?
« Reply #1 on: September 06, 2015, 12:19:42 PM »
Actually, I just erased a whole long post.
The best way to do this is to get the rims and tires you want to use. Set them in the wheelwells so they clear everything the way you want. Then carefully measure the distance between them (mounting surface to mounting surface). Then you have the final length. Then measure and subtract the thickness of the brakes you are going to use. That gives the length of the rear end. Oh, important. Don't forget to take the amount that the axles stick out of the rear housing into account.

Otherwise it will be lots of trial and error and I would then suggest just making the 8.8 the same length as the MII 8 inch and play with the rim/tire sizing.

hth,
Russ
In Glendale, Arizona

RIP Casey, Mallory, Abby, and Sadie. We miss you.

79 Pinto ESS fully caged fun car. In progress. 8inch 4.10 gears. 351C and a T5 waiting to go in.
74 Pinto Wagon.  To be or Not to be a Pinchero, that is the question.

Offline 76hotrodpinto

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Re: Does my rear end look too big?
« Reply #2 on: September 06, 2015, 12:43:16 PM »
That's how I would normally approach this project, but this is my daily driver, so I'm trying to keep it drivable till the last second. It's a 2 week turn around on the 8.8 shortening. And if I go with a 4-link setup too, there's a few weeks there too. The 4-link down time would unavoidable, but I can try to shave time off by not having to tear it all down to fit the wheels and get a measurement for the 8.8.
1976 half hatch 2.3 turbo w/t5.

Offline russosborne

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Re: Does my rear end look too big?
« Reply #3 on: September 06, 2015, 01:37:06 PM »
Ah. That makes things "interesting".
Don't know what to say other than to hope that someone else who has done this chimes in.
Russ
In Glendale, Arizona

RIP Casey, Mallory, Abby, and Sadie. We miss you.

79 Pinto ESS fully caged fun car. In progress. 8inch 4.10 gears. 351C and a T5 waiting to go in.
74 Pinto Wagon.  To be or Not to be a Pinchero, that is the question.

Offline C. M. Wolf

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Re: Does my rear end look too big?
« Reply #4 on: September 06, 2015, 05:39:33 PM »
Well, it can still be measured for correct fit.. much like Russ has described..

Take a day,(or some time), have the rims & tires ready or their exact sizes/displacement, put the Pinto on a lift so that it can be measured from the underside without removing anything except the current wheels. Measuring from center of the vehicle - out to where the new rim-hubs will rest, making sure there will be enough clearance for the whole tire and all it's vertical travel when they are in place,(if you are going to lower the back-end any, this should be considered within the wheel-well for proper fit without rubbing or you'll have to tub it).

If you are not totally comfortable getting these exact measurements to size & cut down the new diff, have a very, very good mechanic that has done some before, do the measuring and even the sizing/cutting of the rear-end. If whomever does the measuring/cutting down isn't willing to fully guarantee his work, take it to one that will. This is not something to play with & it simply must be done correctly, even down to the welds & materials used.

Now when you go to re-spring it, the drive shaft "spin-up" side is going to need to be arched slightly higher than the "spin-down" side, especially if you build the engine with quite a lot of torque in it.. this slightly higher arch will need to compensate for the engine's heavier twist off the line.. otherwise you'll need to build the rear suspension a bit too ridged to compensate for this, resulting in a stiff ride or always having to under-inflate the tires to soften the ride.

Make sure you adequately shock the rear,(I personally like 'Ranchos', they're strong yet still smooth enough to get a good ride & they seem to outlast many other brands)..

IHTH

Michael

Offline 76hotrodpinto

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Re: Does my rear end look too big?
« Reply #5 on: September 06, 2015, 11:05:08 PM »
I think I'm going to go with about 1 inch shorter than the m2 rear end. I'm losing the battle with my ocd about the 4-link... this is going to hurt. I want this thing to be a little stiffer than most would consider a comfortable ride. I am dropping her down 2 inches as well. Crap! If I do the 4-link, I have to do more frame re-enforcement. Hmmm... Take that ocd!
1976 half hatch 2.3 turbo w/t5.