New hydraulic piston too large

   / New hydraulic piston too large #1  

fire5096

New member
Joined
Jul 16, 2025
Messages
1
Tractor
Ford 3000
I just did a hydraulic lid rebuild on my '73 Ford 3000 and my piston was in terrible shape and scarred up the housing pretty good. I ordered a new 3" piston from farmtractorrepair.com and was super excited to change it. My bush hog would drift down and jump back up while mowing. I tried to put the new piston in after honing out the cylinder. It would not even try to fit. I measured with calipers and it measured 3" but when compared to the original you could feel a difference. I didn't have the calipers at that point to measure the original. I took a chance and changed the o'ring and leather on the original piston and put it all back together. As you would imagine, it still drifts up and down. I am confused why the piston is too large or the cylinder is too small. It is the original cylinder. Has anyone else had one of these after market pistons not fit? Any suggestions on what to do to make the piston fit? Also, I changed the relief valve to see if that was the culprit but didn't fix it so I am positive it is the piston.
 
Last edited:
   / New hydraulic piston too large #2  
I just did a hydraulic lid rebuild on my '73 Ford 3000 and my piston was in terrible shape and scarred up the housing pretty good. I ordered a new 3" piston from farmtractorrepair.com and was super excited to change it. My bush hog would drift down and jump back up while mowing. I tried to put the new piston in after honing out the cylinder. It would not even try to fit. I measured with calipers and it measured 3" but when compared to the original you could feel a difference. I didn't have the calipers at that point to measure the original. I took a chance and changed the o'ring and leather on the original piston and put it all back together. As you would imagine, it still drifts up and down. I am confused why the piston is too large or the cylinder is too small. It is the original cylinder. Has anyone else had one of these after market pistons not fit? Any suggestions on what to do to make the piston fit? Also, I changed the relief valve to see if that was the culprit but didn't fix it so I am positive it is the piston.
Maybe the original is metric; 75 or 76mm?
 
   / New hydraulic piston too large #3  
ANYTHING aftermarket is a crapshoot. I'm surprised that YOU'RE surprised it didn't fit. Try another supplier. Might get one from a different part of China.
 
   / New hydraulic piston too large #4  
Welcome to TBN!

If you look at the parts book, the oring for the 3000 measures 2.825" (0.215" thickness + 2.61" inside diameter), so it can't be 3". The only place the roughness of the piston would cause problems is around the oring groove. You can clean the old one up and take the sharp edge off of the oring land.
The cylinder on the other hand, cannot have any grooves of significance or you will get drift/leakby.
 

Attachments

  • 3000 oring.jpg
    3000 oring.jpg
    639 KB · Views: 13
  • 3000 piston.jpg
    3000 piston.jpg
    380.7 KB · Views: 12
   / New hydraulic piston too large #5  
Could you take the new piston to a machine shop and have it lathed down to the correct size? If you do this make sure you take the cylinder along so that the piston can be matched to it. Also the machine shop can check the cylinder to make sure it's not out of round.
 
Last edited:

Tractor & Equipment Auctions

Ford Super Duty Pickup Truck Bed (A49461)
Ford Super Duty...
2011 Ford F-450 Crew Cab Omaha Service Truck (A50323)
2011 Ford F-450...
2006 CHEVROLET SILVERADO 4X4 PICKUP TRUCK (A51222)
2006 CHEVROLET...
2006 KOMATSU D41P-6 CRAWLER DOZER (A51222)
2006 KOMATSU...
Blue-Jet Liquid Fertilizer Applicator (A51039)
Blue-Jet Liquid...
https://www.accessnewswire.com/newsroom/en/healthcare-and-pharmaceutical/nerve-alive-supplement-reviews-inspired-by-nervecalm-for-natural-nerv-1044754
https://www.accessn...
 
Top