The Ford Barn

Tim Ayers · 02-17-2013, 09:40 AM

I posted the same question on the HAMB as well.

More curious for I happen to have both types of cases. Does anyone know for certain if the 81A flathead top loader trans. case with the full length rib (truck & light commercial) cast into the bottom of the case is stronger than the ones with only the "half" rib?

I always thought the weakness in these transmissions was when they get too much fore or aft backlash in the cluster. Once this happens, they bind and grenade. I'm trying to figure out how much the case can do in helping this from happening.

Thanks.

rotorwrench · 02-17-2013, 10:57 AM

Sponsored Links (Register now to hide all advertisements)

I think the weakest spot in the case was between the main input shaft bore and the coutershaft bore at the front of the case. They were known to crack there due to the pressure exerted beteen those two gears under extreme use. If a gear lets go and jams between one of the mainshaft gears and the coutershaft, it can crack or break that front portion of case. The bottom was opened up deeper to fit the larger diameter gears developed for the larger late 30s cars. I've seen several differnces in the castings down there in the rib you speak of but I don't think is really affects the strength of the case overall.

02-17-2013, 09:40 AM	#1
Tim Ayers Senior Member Join Date: May 2010 Location: NJ Posts: 6,181	#78- FH top loader case w/ full rib-Really stronger than one without it? I posted the same question on the HAMB as well. More curious for I happen to have both types of cases. Does anyone know for certain if the 81A flathead top loader trans. case with the full length rib (truck & light commercial) cast into the bottom of the case is stronger than the ones with only the "half" rib? I always thought the weakness in these transmissions was when they get too much fore or aft backlash in the cluster. Once this happens, they bind and grenade. I'm trying to figure out how much the case can do in helping this from happening. Thanks. Last edited by Tim Ayers; 02-17-2013 at 11:25 AM.

02-17-2013, 10:57 AM	#2
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,436	Re: 81A FH top loader case w/ full rib-Really stronger than one without it? Sponsored Links (Register now to hide all advertisements) I think the weakest spot in the case was between the main input shaft bore and the coutershaft bore at the front of the case. They were known to crack there due to the pressure exerted beteen those two gears under extreme use. If a gear lets go and jams between one of the mainshaft gears and the coutershaft, it can crack or break that front portion of case. The bottom was opened up deeper to fit the larger diameter gears developed for the larger late 30s cars. I've seen several differnces in the castings down there in the rib you speak of but I don't think is really affects the strength of the case overall.