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Author
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Topic: more rear end questions
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rmousir
Gearhead Posts: 1124
From: Amelia, Ohio
Registered: May 2003
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posted 11-26-2006 01:31 AM
 
Hi all,Seasons greetings. Taking the advice of the experts here i am going to do the rear end with gears and a locker next summer. I have two or three projects to do this winter first. My questions right now are: 1- how do I tell what size rear end is in the car, (8", 8.8", 9")? 2- what is the difference between all of them? I am assuming that my car is a 8" but I don't know for sure but from reading the other posts today it seems that the 8" is the most common. Also, I see that 3:55s may be the best bang for the buck for me for performance and highway together. Would something like the finds I have seen on ebay work? they are the gears, bearing, and seals. How hard are they to put in. A couple of the posts in the forum mention having a shop put them in. Is this a hard thing to do? Sorry about all the questions, just trying to learn the basics on this. Thanks very much for any and all input. Richard.
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63Kcode
Gearhead Posts: 281
From: Anna Tx
Registered: Dec 2004
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posted 11-26-2006 10:41 AM
I don't know about a 8.8". If you can put a deep socket on the bottom two bolts of the pumpkin then it's a 8". If the socket won't go on then it is a 9".Larry
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Mooney
Gearhead Posts: 2357
From: Marietta, Ga
Registered: Oct 2003
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posted 11-26-2006 10:54 AM
The 8.8 has a rear inspection plate. Your car being a 65/66 wont have this rear end. If it was an original 6 cylinder car it'll have a 7.25 if its an original v8 car minus K-code it'll have an 8in. K-code will have a 9in.
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Ugly 68
Journeyman Posts: 8
From: Las Vegas
Registered: Nov 2006
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posted 11-26-2006 11:04 AM
I race my car some at the track but not all the time so I kept my 8 and just installed an Auburn posi with 3.25 gears. With the c4 I think the 3.25 are perfect since I do drive the car on the freeway and at 80 dont get above about 3000-3500 rpm
Now if I didn't drive it on the freeway I would go for the 3.55 up. I still have not decided if its worth the $$ to put in an AOD the got to 4.11  ------------------
Show And Go Association
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rmousir
Gearhead Posts: 1124
From: Amelia, Ohio
Registered: May 2003
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posted 11-26-2006 11:09 AM
quote:
Originally posted by Ugly 68:
I race my car some at the track but not all the time so I kept my 8 and just installed an Auburn posi with 3.25 gears. With the c4 I think the 3.25 are perfect since I do drive the car on the freeway and at 80 dont get above about 3000-3500 rpm
Now if I didn't drive it on the freeway I would go for the 3.55 up. I still have not decided if its worth the $$ to put in an AOD the got to 4.11
The car is an original 8 cyl car. Nothing special so no 'K' code. So chances are I have a 8" rear. SWEET! Is that better for looking at costs to up the gears and lock or more expensive? I saw a lot of 8.8" on ebay. I assume none of those will work. I will need a set for the 8" rear. What kind of rpms do you get doing about 70 ish on the free way with the 3.25s? What would the rpms be at 3.55? How hard is it to drop in a new set of gears and a posi/track lock? With the help of everyone here (lots of help  ) I put in my motor and got the car running well. Is this job beyond that? I'm still a green rookie. Thanks. Richard.
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rmousir
'66 Mustang Coupe
Ford Blue & white stripes
95 roller 302, C4 Auto
Offy 360 intake & Holley 4 bl carb
grab-a-track 620s, 4.5 leafs, 1.25" drop blocks
[This message has been edited by rmousir (edited 11-26-2006).]
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minnesotamustanger
Journeyman Posts: 36
From: Hutchinson, Minnesota
Registered: Apr 2005
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posted 11-26-2006 12:33 PM
Shouldn't be too hard, Richard. Unbolt and remove the axles,pull driveshaft, unbolt the 3rd member and pop it out, new gasket, intall new one, put axles back in, fill with grease' install driveshaft. Of course this is if you have someone experienced set up the new gears, which is somewhat technical. Mike [This message has been edited by minnesotamustanger (edited 11-26-2006).]
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68 Coop
Gearhead Posts: 5847
From: Mesquite, NV. 89027
Registered: Oct 2004
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posted 11-26-2006 06:42 PM
The 355's will put you right at 3000 rpm at 70. Since my speedometer is off after the change, I can't tell you exactly, but it's close to that. Do you do much highway driving? If so, Ugly 68 had a good suggestion. I've got right at 1000 invested in my pumpkin with the gears, Lok unit, and installation.
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Scott H
Gearhead Posts: 1480
From: Chicago area
Registered: Mar 2005
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posted 11-26-2006 08:17 PM
Richard,
9" are more common to find and are usually slightly less expensive.
8" is what you have and are available, just not as plentiful.8.8 is not designed to fit your chassis and would need welding and fabrication to make it work. If you are swapping out a the center section that already has gears and a locker in it you will be able to do it with no problem. Don't get just the gears because you will need a pro to set them up. If you are looking on Ebay, you DO NOT want the gears with bearings and seals, you woudl rather find a completely assembled center section, also called a pumpkin, a pig, a hogshead, a differential assembly, etc. The key is you want the whole assembled middle part, not just the gears, and you don't need the housing. Some Mustang II's used the same center section, as did some Granada and Maverick cars, lots of 1st generation Mustangs from 65 up to 73, as long as it isn't a 9" or an early 6 cylinder car. The 3.55 Equa Lok rear in my 66 GT came out of a Mustang II.
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rmousir
Gearhead Posts: 1124
From: Amelia, Ohio
Registered: May 2003
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posted 11-27-2006 08:59 AM
Thanks very much for the great informaiton. I will keep my eye out for a complete differental assembly. I still have a couple of projects to do ahead of the gears but when I time comes I will be better prepaired. Thanks very much folks.Richard.
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65 fastback
Journeyman Posts:
From:
Registered:
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posted 11-30-2006 12:05 AM
Richard:
I recently installed a 3.55 LSD gear set from a Mustang II replacing the factory 2.8 gears. You can really feel the difference off the line and freeway driving isn't too bad at 65-70 MPH. There are plenty of calculators out there to determine your revs based on gears, wheel and tire size. Table below shows RPMS based on a 235 x 60 14.
Speed 2.80 Ratio 3.55 Ratio
50 1960 RPM 2485 RPM
55 2156 2734
60 2352 2982
65 2548 3231
70 2744 3479
Hope this helps.
Mike
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rca
Journeyman Posts: 45
From: Dallas, Texas, USA
Registered: Nov 2006
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posted 11-30-2006 11:36 AM
What's the cost associated with changing the rear end gears? Going from a 2.8 to a 3.55, Approx.
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68 Coop
Gearhead Posts: 5847
From: Mesquite, NV. 89027
Registered: Oct 2004
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posted 11-30-2006 04:25 PM
quote:
Originally posted by rca:
What's the cost associated with changing the rear end gears? Going from a 2.8 to a 3.55, Approx.
I was quoted 300 for the change, but with the kit it was right around 450. You might be able to get the kit cheaper from a distributor and save a little. I found a 4 wheel drive place in Utah, so I would just call around out of the yellow pages and see what they say.------------------
William
M&M# 4256
MCA# 64831 68 Coupe
289
C4
3:55's/Trac-Lok
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rca
Journeyman Posts: 45
From: Dallas, Texas, USA
Registered: Nov 2006
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posted 12-01-2006 07:56 AM
That's not too bad. I've put so much money into this car, with Christmas coming up, I'll have to wait until the first of the year. It's killed me on cash.------------------
Step On It Until You Smell Stink!
www.randrews.mustangsandmore.ws
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