Cat 426 Transmission rebuild

Cat 426 7BC02306

Bought this for a low price knowing that it did not move in forward. Had really hoped the FNR was just out adjustment, but the screen was covered in a black material and the fluid looked like milk.

I have limited experience in rebuilding trannies - I did rebuild a 4 cyl Datsun motor back in the day, so this is the first of many questions for the group as I begin to get into this project.

With the help of my BiL, we spent about 6 hours yesterday and got the transmission detached and out from under the machine.

The WSM states “Remove access cover from the torque converter housing. Remove the bolts (15) that hold the flex plate to the flywheel. Insert a screwdriver between the flex plate and torque converter to hold the torque converter in place.”.
Did that and could not get the TC off with the tranny. So the TC is still attached to the engine.

Any idea as to why the TC is hung/stuck? Should I be worried about reassembly problems? When googling I only find references to auto trannies and when reinstalling the TC to the tranny they speak to hearing some clicks which indicates the TC is aligned properly with the pump.

The WSM doesn’t speak to any intricacies in reinstalling the TC.

Thanks for your input -

Ray

I left the fact that I did remove the bolts holding the flex plate to the flywheel out of my original post.

graywarrant said:

Had really hoped the FNR was just out adjustment

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LOL...this never works out. The old saying is "Hope for the best, expect the worst!"

graywarrant said:

Any idea as to why the TC is hung/stuck?

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The pilot bushing should be the only thing left and its a slip fit. Maybe your not using enough muscle and wiggling?

heymccall said:

View attachment 241839

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Hopefully I won't need that special tool for the install. The TC was spinning free with the tranny still installed and that was how I was able to remove the 6 smallish bolts that attached the flex plate to the flywheel. Should be able to reverse when installing and once I have one bolt lined up, the rest should also be aligned.

Ref your second post - yes, I had inserted a screw driver between the FP and TC, but it was bending enough that I felt I had missed something in the steps. Went back through the procedure a few times and spun the TC around 360 degrees a couple of times to make sure I had not missed any of the bolts and still couldn't get it to budge.

As I had help and was loosing light, decided it best to get the tranny out while we could and I would deal with getting the TC out on my own.

Based on Vetech63's input, I'll get out there tomorrow and try to use some more elbow grease and maybe a tap or two with a dead blow hammer to free it from the pilot bushing.

Ray

Elbow grease and some wiggly/jiggly broke it free. Can only think the screwdriver was torquing the TC against the pilot bearing and once I just tried the wiggle/jiggle approach using my hands at the 3/9 o'clock position it jumped right off.

I think had I tried the screwdriver method and repositioned it in various points around the TC while trying to pull the tranny out, that probably would have worked.

I'll be dropping the TC off at a local shop for repair/rebuild and then I'll get the kit ordered and start tearing into the tranny.

Thanks for the help so far, but the journey is just beginning.

Ray

Update on the rebuild process and another random question.

Received the rebuild kit from Joseph Industries. Seems to be a comprehensive kit with all bearings, cups, gaskets, o-rings, etc.. That cost me a bit under a grand. They have other levels of rebuild kits at lower cost, but since I knew I was going to be getting into the clutch packs which requires a total disassembly, I figured I might as well put all new wear parts in and get another 4300+ hours or more out of the machine.

Had some scoring on the transmission pump shaft so I ordered a new one from CTP Parts. I was surprised when the pump arrived in very sturdy packaging and casting on the housing says “Made in the USA”. $206 Win.

Turns out we have a nationally known torque converter builder here in Columbia - Cameron’s TC Services so they have gone through the TC replacing a few worn parts and getting it back to balanced and looking new. $270 Win.

Time for the random question:
Right know I have the innards exposed. Upon removing the inner cover I found this piece of a part laying on the shift fork. It is half of something and has 7T 31 44 marked on it with some radial indentations - 2 on one side, 1 on the other. I can’t find it in the online SIS system so I am looking to the collective in the hopes someone knows what it is, where it goes and a good number to order a replacement.

Thanks for your input -

Ray

item #1 is a thrust washer 7T3144 times 2

I've had a lot of trannys apart & never seen a thrust washer broken like that.
Joe H

Mark250 said:

item #1 is a thrust washer 7T3144 times 2
View attachment 243772

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Thanks Mark - fortunately it wasn't a venomous snake. I was stuck thinking it had to do with the reverse idler shaft as that was all I had pulled out of the case. Never got out beyond looking that and obviously if I had, I would like to think I would have seen it as the first item in the parts list!

Joe H - got me, this is the first one I have been into. I found it strange because it seems to me to be a fibrous material - not steel. Not sure how much force is exerted on that particular washer.

I've got other obligations for the weekend and hope to get back into the next steps the beginning of next week.

Thanks for the quick answers.

Ray

Been a while since I've posted on this project.

A lot of other things have taken priority, but I have finally gotten some time to piece together and move forward on this rebuild. I've gotten three of the four shafts rebuilt, all the new bearing races installed and I was working on the clutch shaft today. Got everything torn down and the forward clutches were (as expected - when purchased the machine would only move in reverse) toast.

Got everything all cleaned up and started with the reassembly and immediately hit a snag installing the outer piston seal - item #17 on the SIS2.0 parts diagram.


The old seal had a groove that was installed facing down towards the base of the clutch basket. I installed the new seal in that same manner. The new seal has a slight outward cant to the seal lip that when I go to install in hits the chamfer that is machined into the clutch basket. Hard to explain/describe, so here is some chicken scratch to help.

You can see that from 3 to 4, the problem is the outward cant of the seal and the angle of the chamfer. I am guessing/hoping that there is some sort of special Spicer tool for the proper installation of the piston/seal as I have already torn one seal trying to shade-tree it into place.

I've ordered a couple more seals and plan on taking both pistons w/seals installed and the clutch basket to my Cat dealer to see if they can get the seals installed without damaging them as I can see no way to do so.

Appreciate your input.

Ray

All I see

Thank you heymccall. I should have mentioned that I have the WSM for the machine.

It is the part "Note: Seal (38) must be completely retracted in its groove before piston (41) is installed." that I am struggling with.

It seems like there should be some tool like a piston ring compressor to get the seal "completely retracted". In my drawing above, item #3 you can see how the seal kicks out past the piston edge just a smidgen which is just enough to catch on the chamfer when I try to install.

I struggled with getting the seal installed, ruined a couple of new seals. I ended up ordering CAT OEM seals and saw no difference between them and the aftermarket seals I had been using (ruining).

I ended up taking it to my local Cat dealer (Blanchard) and the tech was able to get it to pop right in after he went over the clutch basket thoroughly cleaning and polishing all the surfaces. He did use the handle of a hammer (same thing I tried), but he also knew how to correctly hold his tongue while performing the intricate installation procedure and was successful in getting both seals, pistons and the spring assembly (item 15 in parts breakdown shown above) installed. Offered to pay or donate to an employee fund and they wouldn't accept the offer.

Good to find a company and group of folks willing to help someone out.

After a weekend break, I hope to get the remainder of the clutch shaft put back together and then assemble the transmission.

Thanks and happy Veteran's Day.

Another question for the collective:

9W6500 VALVE GP-TRANSMISSION CONTROL has a large solenoid 6T9519 and I am wondering about the correct test procedure for this solenoid.

On other solenoids I would apply 12vdc to a solenoid, the coil would engage and draw the plunger in or push the plunger out and when 12vdc was removed, a spring (or some other mechanical or electrical means) would return the plunger to its normal (unenergized?) position.

With the 6T9519, I can push the small plunger in with my finger and then connect 12vdc which pushes the small plunger back out, but no mechanical mechanism seems to pull the small plunger in on its own accord.

The solenoid was full of fluid (water/trans fluid mix) when I started testing, I've used a heat gun and gravity to extract out of the fluid, but suspect more is inside the unit. I am about to look at it again, but it doesn't appear to be a serviceable part.

Before I order a new one, I just thought I would ask about proper testing if I am not testing it correctly.

Thank you for your input -

he also knew how to correctly hold his tongue
If you're not holding your mouth right it's never gonna work.
Joe H

Joe's response prompted me to relook what I was doing...Thanks.

The way this solenoid works is when 12vdc is applied, the small plunger is pushed out against valve 37 which has the resistance of spring 22 to push the solenoid back in. So instead of an internal spring resetting the solenoid, this configuration has an external spring which accomplishes the same result.

Valve 37 and spring 22 reference the parts diagram available on the sis2.cat.com website.

Given my better understanding of how the solenoid works in conjunction with the valve and spring I've determined the solenoid is working as designed and I have no need to buy a new one.

Thanks for your help.

It has been quite a while since I updated this thread. Thankfully I am not relying on this machine nor my mechanical abilities to make a living.

I have the transmission completely assembled and mounted into the machine.

I get no action with the FNR or gear lever in any position. I have verified that the TC is spinning with the engine running. I am waiting on a couple of gauges to start testing the various ports on the transmission.

Is there a startup procedure that I am missing to prime the transmission pump?

Thanks for your help -