1978 Cat D6D with transmission problem (4x model)

Oilfield Cat · May 9, 2018

I recently purchased a certified rebuilt transmission from IronPeddlers. We had cat come out and assist us with some of the work and also put all genuine cat classic o rings and parts in the machine. Torque converter works as it should and has been tested. All screens and filters changed and clean, all fluid brand new. I have 2nd and 3rd gear going forward and reverse. I do NOT have 1rst gear going forward and reverse. Several mechanics with Cat and others said they have never heard or seen anything like this in their entire career or life of working with these machines. I really need some help before I pull this tranny back out from some one who maybe experienced this issue before? My old transmission wasnt missing gears or ect. When we installed the transmission we did have to pull the top plate to click something in because the machine would not move at all period. After we did that we got movement like normal but after putting the cage back on ect we found out 1rst is missing in both forward and reverse. PLEASE HELP!

jm. · May 9, 2018

You put the shifter in the wrong whole , you are one notch off not closing the 1 gear clutch pack.

Old Magnet · May 12, 2018

There are no holes involved for shifting other than for linkage rods.
Shifting at the transmission involves detents and cams.
Both direction and speed indexing is adjustable for correct position.
There is also a process for adjusting linkage rods to index shift positions.
You need to check out shifting linkage and indexing before any thing else.

AJ. · May 13, 2018

The Cat mechanics that have not seen a D6 powershift with no first gear must be very experienced,first gear failing was a common problem back in the day as it is the most likely as it is used most and suffers from a lot of shock loading,out of the five clutches in the transmission you have only four working,you know that the torque,charge pump,forward and reverse clutches are ok,you also know that two of the three speed clutches are ok,now the issue is with the first gear clutch,the first gear clutch serves both forward and reverse,the clutch is either not been engaged or there is a mechanical issue,a pressure test is the first thing to do to see if the hydraulic end of things are ok,with the control valve selecting the other movements it's unlikely it's the linkage but,but,why did ye have to go into the rebuilt unit?,test the pressure and see what it's says.
AJ

1978 Cat D6D with transmission problem (4x model)

Oilfield Cat

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jm.

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Old Magnet

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AJ.

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