Should I keep the old rear axle?

[JTG 10]

I have a '69 Mach I. It's a base model that was a 351W, 2bbl, auto with an 8" rear with drums. I'm doing a full restoration. It's down to the shell now and on a dolly. I planning to put in a 9" posi with disc brakes, most likely going to get a new full setup. The eventual engine plans are to put in a stroked 351W nothing over the top but with some muscle to it.

 

Is there any reason to keep the old axle? I've had the car for 25 years and have no plans to sell it once it's up and running. I can see keeping the auto trans when I move to a t5 but I don't see any scenario where I would want the old rear in the car.

 

What do you guys think?

[LiLMike 42]

I would sell it. I would also sell the tranny, no sense in keeping that either just for the facts that you stated.

[Rsanter 152]

If you ever think you may restore the car to all original then keep the stuff.

If not then sell the stuff

 

Bob

[michael2938 24]

My vote is to keep it if you have the room to store it and keep it out of the way. The next owner of the car might want to restore it back to original condition even if you don't. It at least keeps that as an option on the table.

 

Is that original to the car? I thought all Mach '1 came with a 9" rear?

[69droptopgt 10]

The tranny should be vin stamped to your car. I would keep it. Rear wont have a vin on it so not as important. I don't think all mach1 came with 9 inch but unsure on that question.

[Brian Conway 264]

I pretty much like to keep all the parts. Even the broken/replaced ones. This particular 8" probably came with a 6 cyl. car. The 8" axle housing, as mentioned, carries no markings so not critical for any future restorer. Brian

Edited September 15, 2014 by Brian Conway

[stangs-R-me 120]

All 1969-70 351W 2BBL on up came with a 9" rear as STD, so that would mean all '69 Mach 1's & GT's came std. with a 9" as STD. in 1969 since 351W-2BBL was the base engine for these models.

 

If your car has an 8" in it now, it is NOT ORIGINAL anyway as someone swapped it in at some time in the past.

 

There were TWO levels of 9" though in 1969 ...

 

428CJ/SCJ, Boss 302 & 429 came with 31 Spline 9"

and

351 & 390 came with 28 Spline 9"

 

Doug

[michael2938 24]

Since it is not original to the car then, I see zero reason to keep it around. I know my car originally came with a 302 and an 8". But was pretty sure the 351/Mach 1 cars had the 9", just wasn't sure where I read that.

[JTG 10]

Now you guys have me doubting what I have. I need to look a little closer. I thought it was original to the car. I also had it in my head that since it was an open rear it was an 8".

[maxum96 32]

All 1969-70 351W 2BBL on up came with a 9" rear as STD, so that would mean all '69 Mach 1's & GT's came std. with a 9" as STD. in 1969 since 351W-2BBL was the base engine for these models.

 

If your car has an 8" in it now, it is NOT ORIGINAL anyway as someone swapped it in at some time in the past.

 

There were TWO levels of 9" though in 1969 ...

 

428CJ/SCJ, Boss 302 & 429 came with 31 Spline 9"

and

351 & 390 came with 28 Spline 9"

 

Doug

 

 

Correct

 

 

OP, post some pictures of the center section and we'll tell you which rearend you have.

[JTG 10]

Here are the pics. It looks like an 8" to me. And if all Mach I's came with a 9" then this is not my original rear.

 

 

 

[maxum96 32]

Yup, that's an 8". You sure your car isn't a fastback that someone did up as a Mach 1? That's every unusual to have an 8" in place of the factory 9". Ever got a Marti report on your car?

Edited September 20, 2014 by maxum96

[JTG 10]

Yeah, it's a Mach I. Here's the door tag. The engine was not original when I bought it in '88 and the front fender was replaced but everything else looked stock.

 

[Max Power 74]

Now you guys have me doubting what I have. I need to look a little closer. I thought it was original to the car. I also had it in my head that since it was an open rear it was an 8".

 

There are far more open 9" rears in this world than Posi units.

 

The easy way to tell is that you can stick a deep well socket straight on to all the bolts on an 8", but on a 9" there are a couple you can't.

 

Here is a crude video illustrating it:

 

Your door tag says you should have a 3.00:1 axle, not the 2.79 on the axle tag, so it looks like somebody probably salvaged a 302 equipped car axle somewhere along the way. That's pretty unusual, 9" diffs are pretty indestructible.

[maxum96 32]

Yeah, it's a Mach I. Here's the door tag. The engine was not original when I bought it in '88 and the front fender was replaced but everything else looked stock.

 

 

Don't go by the door tag alone. Go by the dash VIN. Doors get switched on 45 year old vehicles all the time. Is the door tag VIN number the same as the dash VIN?

[Hoover 12]

You might do better to keep it, and when you run into a deal, it can be used as trading or bartering stock. You will probably get more for it in a trade.