This is interesting as I was looking at 9" rearends today. Rebuilding our 351w with an Edelbrock top end kit in April(ish) and figured we'd have to upgrade to a 9".

Could I simply order the TrueTrac for an 8" rear and get away with this for now? No track use just a fun daily driver.

 

Yeah, a little. The TKO's have a square top, as opposed to the rounded top on the T5 and toploader. In a 65-66 you basically have to relocate the tunnel. In a 67-70 you can do the same, although you mightcould get away with banging it out with a hammer. The other option is to use a drop crossmember to gain the needed clearance. JMD has done this and says he has no problems with it, but I'd still be concerned about altering the pinion angle by that much. I'm going to use the drop crossmember, but I'm also doing an 8.8" conversion at the same time, so I'll just have the spring perches welded on to the 8.8 to compensate for the change in pinion angle.

 

i think the main thing, would be traction, if you are running slicks with a 347 and a 8inch, it will be more prone to grenade than if you were running drag radials or street tires... i would go for a 9in myself if i were you just for the extra insurance, why build it twice when you can spend a little bit more money, have a stronger rearend and have it last?

 

Lots of interesting comments and information.

How long it lasts depends more on how it's driven than anything else.

As far as an automatic preloading and a manual NOT preloading, it depends on how you set it up at the line. Back in the sixties and seventies I saw lots of drivetrain damage due to drivers not preloading at the line. All you have to do is ease out the clutch lightly at idle just enough to feel everything load up then disengage the clutch again, and rev up to get ready for the light. NOT doing this gives enough slack to slam everything hard and tear up who knows what. It might be the driveshaft, an axle or worse.

Common sense and a feel for machinery adds a LOT to the longevity of ANY machinery whether it's a drag car or a fork lift.

 

I have the true trac on an 8" with 4.11 gears. 351w with edelbrock top end kit. So far I have had no problems with the 8." My dad also has 5.0 66 with an 8" pushing 300hp and its his daily driver. I think the 8" can handle alot of abuse before they break.

 

I am glad to hear that the 8in can handle some abuse. I have just purchased my 69 with a 351c and was disappointed to find out that it had the 8 instead of the 9. I know my style of driving and true track and some gears will do me just fine. I am planning on an AOD swap over the winter.

 

I had an 8" with a traction lock and 3.50 gears behind a 345HP Ford crate angine and a Tremec 5 speed with no problems at all.

I also have a 9" pumpkin with a traction lock, 3.89 gears, and set up for 28 spline axles for sale if you are interested $600.