Allison 5spd & 6spd Identification

[GMC 08]

I need some insight on how to clearly tell the difference between a 5 spd Allison and a 6 spd Allison. Specific numbering in the part number or serial number possibly? I am planning on getting a junkyard transmission and I’d like to verify it’s a 6 speed before purchasing. I guess I don’t trust some of these salvage yards.

Thanks!

 

[ryan415]

A 5 speed will have a external PRNDL switch or Park-Neutral safety switch. A 6 speed will be internal. It is the switch mounted on the left side with the selector shaft. Hope that helps:thumb:

 

[GMC 08]

Thanks....That helps. Any pictures of a 5sp and 6sp?

I have a ATSG manual so I 'll look at it tonight.

 

[Mike L.]

Look at the tag on the Alli. Look at the date. The first two digits will tell you the year. The letter after that will tell you the month and the next two digits will tell you the day.