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I have to confess I am clueless right about now!! I am by no means a mechanic and have to rely on others when it comes to things like this. I have known the man who is actually doing the work for many years and trust him completely with what he says. It very possibly could be that my car does have a 6.5" rearend. I will get back with him about how and where the torque arm mounts to the rearend and post back on here. For clarity I have a Monza Towne Coupe, not a Vega. I do appreciate all the advice and comments- as I said I have to rely on others.

Another thing to measure, the outside diameter of the spline on the Monza rear end you have and the spline on the 26 spline S10.

Dick

Ooops, sorry this thread got started by someone with a vega and then got switched. I am confused too because I believe all Monza's came with 7.5" rears, but I would suggest we figure out exactly what you have before going further. Maybe someone can suggest how to distinguish between a 6.5 and 7.5 better than I can.....stick with us and we will get it figured out. Do you know how to post pics here? Maybe that would help.

Did some searching and all 1975 Monzas came only with the 6.5" gear. Guess that explains that!! Can't use the old housing because it is too small in diameter so naturally I will have to go to the 7.5" so the new question is what else do I need to get all this fixed and back on the road?

Well while it has been discussed before it is not true that all 75 Monza's came with 6.5" rear. I ordered my car right when they were introduced in Sept of 1974 and it came with a 7.5" rear. It does sound like yours may indeed be a 6.5" though, that would explain the situation. I would still like to know how your torque arm is mounted to the rear end, 2 long through bolts or 4 short ones. Easiest way to tell is to look and see if there are 2 large nuts on the bottom of the arm, if so that indicates it has the 2 long bolts......

I am remembering that the 4 Cyl. cars came with the smaller 6.5" rear for '75 and possibly '76 [rare though] my '75 Monza mistake had the 6.5 if I remember correctly. Harry

Right now I think the best bet would be to just try to find an entire rear end and call it a day. I may have found one about a hundred miles from my house and need to check it out. If I do buy it the main trick is going to be how I get it back home in my Honda Civic....

That would be the easiest solution and for the most part will bolt in. Keep in mind that 75's used a different panhard bar (curved) vs the 76 and later straight bar. That shouldn't pose too much of a issue but try and either get the panhard bar with the rear or be prepared to swap your current axle brackets on to the later housing. You may want to check and see what gear ratio it has as well just so you know........you will get the benefits of the larger rear brakes as long as it is a 76 or later 7.5" rearend.

You will need to shorten drive shaft when you change to the 7.5 rear . 2 long bolts will be needed to attach the torque arm instead of the 4 stubby bolts .On my car I was able to reuse the torque arm with out shortening it.

If you are in or near Central Florida, or close, I will not be using the 76 or 77 Monza 7.5 extra rear end, and it is available with 4 lug axles, backing plates, brakes, complete. PM me if you are interested. It is a 4 link type without the panhard bar and comes with the sway bar.
..After persuading the new s-10 backing plates to allow for proper flush mounting of the s-10 wheel cylinders, and inserting our s-10 5 lug axles, we now have a distance between the backside lug studs and the wheel cylinder of approx. 4 credit cards width which should be plenty.

spencerforhire wrote:Or is it possible that there's a Vega 6.5" housing in the car?

I guess I called it. lol
I did not know that any Monzas came with the 6.5" diff. Learn something new every day.

It's really pretty strange because I have been following Monza's since they were introduced. Remember, I ordered mine in Sept 1974 as soon as they were introduced. I had every article written on them and one of the big changes for 1975 Monza's Skyhawks and Starfires was the new 7.5" torque arm rear. I truly believed that all Monza's as well as Starfires and Skyhawks came with the 7.5" rear. Maybe some got the 6.5", but it sure was my understanding that they all had the 7.5". A lot can happen to a car over 40+ years, I would love to see some documentation that states a Monza, Starfire or Skyhawk came with a 6.5". Maybe some 4cyl ones came with them?

Clyde the factory service manual shows them with both torque arm mounts and I am sure my '75 2.3L Auto was the small one, I think my '76 Skyhawk 3.8L oddfire Auto was too, but those were both a long time ago! The 6.5" was in production until the end of the Chevete, so it could have been placed in anything that it fit, maybe just to use up left over stock?. Harry

I can understand depleting the 6.5" stock in Vega's as that's what they always came with. It just seemed that with the introduction of the H "special" cars introduced in 1975 one of the new improvements was the 7.5" torque arm rear. It's the same with the solid front rotors, ventilated ones were never installed in Vega's despite being installed in the other H bodies after 1975. I assume that was also a inventory issue.....

The 6.5 axle has 23 splines. So, for the definitive answer, since the axle is out. count 'em.