T 20 transmission in Big Max II

[chris lewis]

Hello everyone,
I have been hashing it out over in the engine forum with my freshly rebuilt JLO 440. Thanks to the help of the folks, I got it running. Albeit, it is not 100% yet but I did get it running enough to drive my MAX for the first time.

History: I bought the Max 3 years ago. The PO told me he had it a short time and the engine seized up. Long story there, regardless, the engine needed an overhaul as he melted a piston.

Fast forward 3 years and here we are:
I got it running and tried to drive it..and it would not move. I checked the fluid and it was low.
I bought some frsh Mercron Dexron and some limited slip lube and made a blend and topped off the transaxle. Now it would move.

First thing:::the sticks are both all the way forward. When I gave it throttle, it would sort of started moving forward...but if I tried to turn it, it would bog down....and then sometimes it would turn.
I did get it moving and gave it the juice and the thing really took off...but then turning it was a bit difficult. I drove it around and it seemed to want to turn a bit to the right...I did note that one of the 3 right tires (middle one) was flat..they are al weather checked and should be changed...this middle one will no longer hold air.
Additionally, sometimes it would turn well...and other times it would act like the brake was on and it would just lock up and not turn even though it felt like it wanted to go.
I can put it in reverse and forward...it does move but then sometimes it seems as if the brake is on....just like when I am turning it.

I am a complete newbie to these things...I bought this on a whim as 39 years ago I , my Dad and brothers saw them racing at the Ohio State Fair.I always wanted one...so here I am. I have rebuilt VWs, vespas, old Gravelys etc. so am not mechanically inept...I just do not know the ins and outs of these fantastic machines yet.

[thebuggyman1]

I think you need to crack the t-20 open and take a look inside. It may have been fine 3-4 years ago, but I've seen them rust up inside just from sitting. One had sat for a year, and had maybe half a thimble full of water in it when torn down. Another was a fairly fresh rebuild, it looked like they stored it on the dirt floor of a barn, but had zero water inside. That one rusted with the band material sticking to the drums, and when peeled apart, half remained stuck to the drum. Both required ALL new bearings, and the drums turned.
Good luck

[Bazooo guy]

Heres some info on the t20 .

http://www.6x6world.com/images/skid-steer-manual/Borg-Warner-Skid-Steer-T20-Manual.pdf

[chris lewis]

Hi all,

I really do not know too much about these but where should the handles (in rest position) be positioned?

Also, if you have the engine running and you have it in gear (forward or reverse), does the machine creep forward or should it sit stationary?

Thanks for your help...I am stoked that the thing runs!

Chris

[chris lewis]

Hi all,

I tore down my t20 out of the BigmaxII. I have no idea if it is a new model trans or an early as it has been rebuilt at least once and there is no tag on it. It has been painted gray so there are no visible markings on it.

If you read my first post on this, the symptoms were that it felt like it was binding or the brakes were on when I would turn...and if I would brake the one side, and tried to turn, the engine would sometimes bog down and quit...This would happen ieven in forward motion as well.

Here are some shots of the inside. It looks very clean. Bands look good, drums look good EXCEPT for the outer portion where they slip into the bronze sleeve. The portion on the drum that slips into the bronze sleeve is scored up..as if there was grit in there. Both sides are like that...I have a spare set of drums which have surface rust on them and they are not scored.

[hydromike]

Your transmission looks pretty good inside. I wouldn't worry a "whole" lot about the scoring on that part of the drums. While it's not completely ideal, I've run T-20s for years with similar (maybe worse) scoring. As long as there aren't big, sharp-edged grooves that will destroy your bronze bushings, I think it's usable. This certainly wouldn't cause the bogging issues when you're steering. I'm thinking the issue is somehow related to the engine itself, or clutches not disengaging. That is, you're trying to turn with the clutches stuck "open", and in a higher gear. Does your Max still have the springs on the laterals that pull them forward? Is there a possibility that your chains are intermittently binding on one side of the machine? What's the overall condition of the chains. Are they tight enough to not flop around in the breeze?

It looks like you have the earlier version of the transmission, with the supported main shaft. I see a needle bearing on the left-hand output shaft....

[chris lewis]

Mike,
The scoring is not jagged...just rough. Are there pictures of early versus late model transaxles? By stating that it is a supported main shaft, is the support that center portion on the plate?
now that I disassembled it and need to get a new seal kit, should I pull the axle halves out and replace the seals even if they are not leaking?
How do the clutches stay "stuck" open?
how thick should the bands be? These were .095 with the steel band.
Re the chains, they are brand new...but they are from China (they were on it when I got it...and I have read the posts about how bad Chinese Chain is..) I machined new nylon glide inserts for the tensioners and they work very well..holding the chain under tension. The unit rolls easily when it is out of gear so I am not positive where the bind could be coming from.

Thanks for the input!
Chris

[hydromike]

By stating that it is a supported main shaft, is the support that center portion on the plate?

No, it's the needle bearing on the right hand side (mistakenly said left in my previous post) output sprocket. You can see it in this picture....

now that I disassembled it and need to get a new seal kit, should I pull the axle halves out and replace the seals even if they are not leaking?

That's up to you. It's not a bad idea, but not totally necessary. They're not horribly expensive, and it's not really a huge pain to do.

How do the clutches stay "stuck" open?

The bushings that the movable portions of the clutches slide on can get worn/dirty and be difficult to close under the normal (at rest) spring pressure.

how thick should the bands be? These were .095 with the steel band.

I think that 0.100" is new on a standard band, but I'd have to re-read old posts to double check. You should be in fine shape.

As a whole, I don't think the binding is related to your transmission. A a minimum, it's good peace of mind that you tore it apart to check the internals, and gained valuable information on how it's constructed and operates. Pretty simple, robust transmissions, ay?

[chris lewis]

The lateral springs are in place...although I am not sure if they were adjusted correctly...Is there a way to determine that? Some type of spec?
I have decided to take the tranny all the way down and replace the output shaft seals etc. Might as well while I am in there.
Is there any difference for parts between early and late transmissions?

Thanks
Chris

[thebuggyman1]

The lateral springs are in place...although I am not sure if they were adjusted correctly...Is there a way to determine that? Some type of spec?
I have decided to take the tranny all the way down and replace the output shaft seals etc. Might as well while I am in there.
Is there any difference for parts between early and late transmissions?

Thanks
Chris

Some people remove the lateral springs for better "feel".....The problem with that is you must always push on the sticks to engage the trans.

Yes, there are differences in the t-20's thru the years....Specifically what parts are you asking about? Seals and bearings are the same.

[chris lewis]

one thing i did notice on the max when i first drove it was the fact that the handles were all the way forward and the springs held them that way...so in theory, the bands were essentially riding the drums...is that the way they should be...under tension but not too much?

i read somewhere that you had to give the year and number of th transmission to the band relining place so that they could reline them with the correct thickness material. since my trans was rebuilt and is missing all of the id numbers, i cannot tell them what year it is...

thanks,
chris

[jpswift1]

Chris, since yours has the supported main input shaft and the "tongue depressors" that work the plungers it's most likely an early 1970's model. These never had ID plates on them, just number stamped into the cases.

[thebuggyman1]

Chris, since you have the trans apart now, take a look at the internals and imagine the input shaft rotating. This turns the sun gear, which turns the planetary gears the opposite direction. the planetarys turn the drum with the ring gear in that direction. if a band stops that drum (ring gear) it forces the planetary drum to be the one to rotate. If a band stops the planetary drum the ring gear drum will rotate. If both bands were loose, both drums would rotate in opposite directions(diamond shifter in nuetral). If in gear the resistance would force the other drum to rotate. The shift collar will engage either the ring gear drum or the steel plate over the planetaries to determine which drum is attached to the output sprocket. Sorry I'm not a good teacher/or explain things well, but I hope this makes the t-20 a little simpler now.
I forgot to mention: each case half of the t-20 is an independant trans, joined together at that center plate/with the input shaft being the only thing in common.....this is what makes the t-20 so fantastic.

[russriders]

Hey Chris if u are the one live in south Carolina and give me a call I can come over and give u a hands onur t20

[chris lewis]

Hey Andy! Yes...I finally got it running but thought I had tranny issues. So trans is all apart on my bench at work and at home.

When I get my parts I will let you know...Thanks for checking in.

Chris