Does anyone know what the actual axle diameter is on the axles for the automatic vs. manual transmissions? I checked an old thread and found data sheets on them but they only reference the number of splines (29 splines on the automatic, 32 splines for the manual). I have my original axle and it measures .939 over most of it's length, while the aftermarket replacement measures .989. They are both for the automatic. I already snapped the axle once, I'm trying to upgrade to a larger diameter axle if possible. They both have the 29 spline ends, with an OD of .925. Any chance the axle for the manual gearbox is heavier?

quote Originally posted by jsantini: Does anyone know what the actual axle diameter is on the axles for the automatic vs. manual transmissions? I checked an old thread and found data sheets on them but they only reference the number of splines (29 splines on the automatic, 32 splines for the manual). I have my original axle and it measures .939 over most of it's length, while the aftermarket replacement measures .989. They are both for the automatic. I already snapped the axle once, I'm trying to upgrade to a larger diameter axle if possible. They both have the 29 spline ends, with an OD of .925. Any chance the axle for the manual gearbox is heavier?

Yes the axlesfor the manuels are thicker that the auto. Did you snap a stock axle or an parts store axle?

I snapped a new one I got from Advance Auto. I had assumed the auto transmission version would be thicker to handle the extra torque from the converter, but I guess not. Is the axle .999 diameter? I have the book "High Performance Fieros" and they show a drawing of what I assume is the actual axle shaft.

I've got several of each on a shelf I can measure up for you tomorrow if no one else has chimed in by then.

Thanks a lot. That would be great.

quote Originally posted by jsantini: I snapped a new one I got from Advance Auto. I had assumed the auto transmission version would be thicker to handle the extra torque from the converter, but I guess not. Is the axle .999 diameter? I have the book "High Performance Fieros" and they show a drawing of what I assume is the actual axle shaft.

I figured you where going to come back with saying it was an auto parts axle....Did it happen to snap near the end where the splines are? This is common with aftermarlet part store axles as they are usually thinner where the splines are and cheaper made. Use a stock 20 year old Fiero auto axle and you will have no issues with snapping axles as long as your setup is mounted correctly....

Interesting, because the axle that came with the car (looks to be original, but....) is actually a smaller diameter than the aftermarket axle. The original had a diameter equal to the bottom of the splines (roughly) while the aftermarket one seems to have a diameter close to the top of the splines.

quote Originally posted by jsantini: Interesting, because the axle that came with the car (looks to be original, but....) is actually a smaller diameter than the aftermarket axle. The original had a diameter equal to the bottom of the splines (roughly) while the aftermarket one seems to have a diameter close to the top of the splines.

That sounds about right but the original axles are 100% tougher than the aftermarket ones you buy from the parts store..>where did the axle break at?

I can believe that. The aftermarket ones were imports. It broke right at the groove for the rubber boot, about 6 inches from the end.

quote Originally posted by jsantini: I can believe that. The aftermarket ones were imports. It broke right at the groove for the rubber boot, about 6 inches from the end.

Well believe it....It has been said many times and many have had the same issue as you have had. Myself along with many others run stock 20 year old auto axles on 300 plus HP swapped Fiero launching off drag radials cutting 1.4 60' without breaking the axles. If you don't want to have any more issues with breaking your axles then switch to a stock auto axle......