Farm Equipment - 8550 transmission help

8550 transmission help

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=166282
Printed Date: 06 Jan 2025 at 6:11am
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Topic: 8550 transmission help

Posted By: Dakotab19
Subject: 8550 transmission help
Date Posted: 01 Dec 2019 at 10:49pm

Hi all new to the forum here, looking for some help and info on an 8550 Allis.

Quick rundown on the situation: the tractor is sitting in our barn currently and has not been used for around 8 years. It is an 8550 with the original transmission and an 855 Cummins motor swap. I am looking to use the tractor again as we recently returned our planting tractor on lease and i now need to pull our roller tractor to do the planting tractors job, it would be nice if i could use the 8550 to pull the roller (40 ft Mandako).

The current problem i'm having with the tractor is that it pops out of reverse gear.

I was wondering if anyone has any info on these tractors transmissions, and if anyone could share some info on what the cause of this could be and how it can be fixed. Diagrams would also be very much appreciated. Currently were still doing harvest but i'm looking to get some preliminary ideas so that i can check for symptoms before i power wash the tractor and put it in our shop to work on it.

Any help would be much appreciated, thanks!

Replies:

Posted By: DrAllis
Date Posted: 02 Dec 2019 at 11:01am

I'm not an 8550 guy, but it could be a bent reverse shifting fork, OR the fact that the shift lever linkage from the cab down to the transmission isn't adjusted properly or WORN/LOOSE and not getting it 100% into engagement. 2nd gear and reverse are the farthest throw/stroke gear selections for the shift linkage, and if things are out of adjustment and/or worn that might be all it is. Hopefully it hasn't jumped out of gear very many times, or the gear teeth could be damaged beyond being useable. Farm implements work best going forward. Using reverse (under any load) would be a low percentage thing for me.

Posted By: Dakotab19
Date Posted: 02 Dec 2019 at 5:59pm

So it would probably pop out of 2nd if misadjusted then?

Posted By: MACK
Date Posted: 02 Dec 2019 at 7:50pm

AC made a tool for aligning transmission top. Never used it, but it hung on wall of special tool room since 1973. MACK

Posted By: SteveM C/IL
Date Posted: 02 Dec 2019 at 8:39pm

So MACK,wing it or never work on that model?

Posted By: DrAllis
Date Posted: 03 Dec 2019 at 6:56am

There is only so much stroke in the shift lever. So, if it isn't going into reverse all the way, it surely is going all the way into 2nd, unless the linkage is loose or worn.

Posted By: MACK
Date Posted: 03 Dec 2019 at 9:09pm

Just never needed the tool. 7000 series transmission (except a 7000) was almost bulletproof. MACK

Posted By: Dakotab19
Date Posted: 04 Dec 2019 at 10:57am

Is there a procedure to check the linkage, also if i wanted to check the shifting forks can I do it through the cab floor or from the ground?

Posted By: DrAllis
Date Posted: 04 Dec 2019 at 12:13pm

The shift lever must fully 'detent' in 2nd gear and reverse. Anything short of that means the linkage is loose/worn and not centered properly for neutral. The linkage parts that wear are external and not inside the transmission (as a rule).