RK 55 Fittings

Rainbow Hills Winery · May 2, 2019

i have a RK 55 tractor and would like to know if anyone knows what the fitting/threads are on the Transaxle /Hydraulic fill port on the back of the tractor.
the fittings that come with it are plastic, i cannot find what it is after taking the plug to several hydraulic shops and also trying to figure it out myself using calipers and thread gauge.
is this something special that can only be purchased through Rural King?

thanks in advance for any help

jayincmh · May 2, 2019

These tractors are made by TYM. Can't imagine it would be anything special. RK recently posted all of the parts manuals online for their tractors. Check the website...the parts manual may have the info you need.

Rainbow Hills Winery · May 2, 2019

Thanks for the reply jayincmh, i did look up the parts PDF and found the part i was looking for but it dose not have the size, it just states "oil plug". i have bought standard pipe fittings and they don't fit.
ultimately what im trying to accomplish is a return hose from my post driver going into this fill hole where the oil fill is, im having no luck.

g8erh8er · May 2, 2019

Calipers didn’t reveal thread dia. and pitch? Or they did and you just can’t find a match?

Rainbow Hills Winery · May 3, 2019

g8erh8er said:
Calipers didn稚 reveal thread dia. and pitch? Or they did and you just can稚 find a match?

thanks for the reply...
the major diameter was 1.153 and the pipe thread chart i had was either 1.188 to 1.125 i think, nothing real close to my measurement.
it just occurred to me this could be a regular thread and not pipe size....i was just assuming pipe for some reason.
i need to check.

snymat68 · May 3, 2019

Rainbow Hills Winery said:
thanks for the reply...
the major diameter was 1.153 and the pipe thread chart i had was either 1.188 to 1.125 i think, nothing real close to my measurement.
it just occurred to me this could be a regular thread and not pipe size....i was just assuming pipe for some reason.
i need to check.

I'm thinking it might be an M30 thread. What's the pitch (or TPI)?
Standard M30 thread pitches are 3.5, 2, & 1.5 (mm of course).

Per the machinery's handbook (27th edition, page 1801)...

External Thread --- Maj. Dia. Min. --- Maj. Dia. Max.
M30 x 3.5 --------- 29.947 ----------- 29.522
M30 x 2 ----------- 29.962 ----------- 29.682
M30 x 1.5 --------- 29.968 ----------- 29.732

Granted 1.153" = 29.286 mm, but it's the closest I could come up with.

Have you measured the major diameter at both ends of the thread? Is it tapered? If so, it's definitely a pipe thread of some kind.

I'm just leaning toward metric since it's made in Korea.

Rainbow Hills Winery · May 3, 2019

Thanks synmat68, the plug they put on all the fill ports are plastic and only have a couple threads, it does not appear the female side is tapered.
Its hard to guess the TPI with so few threads and i haven't put a thread gauge on it yet. This fill plug is on the trans / hydraulic back by the 3 point system.
i found the part number in the PDF parts list but it does not have the technical information, just says "Fill Plug"

Leo182 · May 3, 2019

Don't know if this will help any, but I broke a fitting on my RK37 backhoe. I went to 9 different shops and nobody could find a standard or metric fitting of the right size. Finally found the part and was told it was British pipe thread.

snymat68 · May 3, 2019

Leo182 said:
Don't know if this will help any, but I broke a fitting on my RK37 backhoe. I went to 9 different shops and nobody could find a standard or metric fitting of the right size. Finally found the part and was told it was British pipe thread.

Just checked the handbook again. Don't think that's it in his case. None of them are close to his measured major diameter. Also, I doubt they'd use a pipe thread for a non-pressurized cap like that. I'm still pulling for the M30.