Need to push hard on t20 laterals to move

[Surfer Dude]

Hello,

Over the winter I took apart my t-20 to replace a broken band and had all other bands relined. Redid all seals and bearings and also pinned the u-channels on the front of the transimission. Everything seems to work fine. Only thing I notice is that the bands seem to require more operator pressure on the laterals to get the same results as before. In order to say pull a heavy load I need to push way harder to get the bands to stop slipping then I used to and its way harder then my other machine. I used the correct atf type F fluid. little less than a quart and about 4 oz of friction modifier. Anyone have any ideas for me? Maybe needs bands tightened more? Less friction modifier?

Thanks Daniel

[hydromike]

Hey Daniel,


Did you do anything to the drums when you put the transmission back together? "Roughing up" the drums when you put the transmission back together is a good practice, and helps the bands grab them more easily. It doesn't take too much; sometimes just some 200-300 grit sandpaper on the drums to get rid of the highly polished surfaces. It's a lot like replacing brake pads on a car without either turning or replacing the rotors. The old units are typically polished right up from all the use, and the new friction material doesn't grab that easily without a lot of effort.

[Mike]

I would go back through the band adjustment procedure again and see if that helps at all.

[Surfer Dude]

Hey Daniel,


Did you do anything to the drums when you put the transmission back together? "Roughing up" the drums when you put the transmission back together is a good practice, and helps the bands grab them more easily. It doesn't take too much; sometimes just some 200-300 grit sandpaper on the drums to get rid of the highly polished surfaces. It's a lot like replacing brake pads on a car without either turning or replacing the rotors. The old units are typically polished right up from all the use, and the new friction material doesn't grab that easily without a lot of effort.

Hydro, I did not use sand paper on the drums to scuff them up because I was worried that rough of a surface would premature wear the bands. I did however use a fresh green scotch bright to dull up the finish. Maybe not enough you think huh?

Mike, I will retry band adjustment. I kind of wanted to do it again anyways so this will give me a reason too

thanks and open to more opinions.

[phabib]

I just closed the case on my T20 after replacing seals, gaskets, and bearings but I did not think to roughen up the drums. My bands were not worn at all and the drums looked good so I left all of that alone. Should I tear it open again to sand the drums a bit or just leave it be?

[hydromike]

I think you can just let it be. Just to clarify what I mean by "roughen up", it's basically just getting rid of a "highly polished" condition on drums after they've been through the ringer. When a transmission is put together new, the drums certainly aren't "rough" by any means, but they don't have very high polished appearance that you get when they've been used for 20,30 or 40 years. If I'm putting a trans together with new bands, I typically throw the drums in the lathe quick and just run a piece of emery cloth over them for a while to give the bands something to "bite to". They're still exceptionally smooth after this process, but it's just not "polished", if that makes any sense.

Daniel's issue might not even be related to what I'm talking about, but I've had brand new bands on an older, not "reconditioned" drum and had the same problem. 4oz of friction modifier might also be part of the issue. I think it typically calls for about an ounce or so. It also takes a little use for the modified to get fully circulated through the system, and there might be some of it concentrated on one of the bands below the fill plug.

[phabib]

Thank you. Does the friction modifier make the ATF slipperier or grabbier? I'm thinking I'll go with a synthetic ATF that says its good for limited slip applications which has modifier already mixed in as part of the recipe.

[hydromike]

It makes it a little bit slipperier. It helps address bands that chatter (grab-slip-grab-slip in rapid succession) on some machines.

[phabib]

Thanks. That explains a lot. One of my cars uses ATF in the limited slip diff and they require that it has the friction modifier. The Redline oil rep told me to use the ATF with modifier, then add extra modifier only if I got chatter from the diff during hard cornering. Not that you do any hard cornering when driving a MV-1.

[Surfer Dude]

I think I will try draining the oil and putting in less friction modifier first. If I get any kind of chatter I will add as needed till the chatter stops. I will keep everyone posted. thanks mike

[amphibious drew]

I think I will try draining the oil and putting in less friction modifier first. If I get any kind of chatter I will add as needed till the chatter stops. I will keep everyone posted. thanks mike

Good idea. Maybe even don't put any in to start. There is probably going to be enough residual left on the bands and in the transmission to keep it from chattering.

[Surfer Dude]

Good idea. Maybe even don't put any in to start. There is probably going to be enough residual left on the bands and in the transmission to keep it from chattering.

I was thinking the same thing. Going to do this in the next few days and will let everyone know how it turns out

[brian v]

I just picked up a max 2 and it is really grabby then it bites in I thought the bands are junk so the friction modifier might be all it needs ?

[Surfer Dude]

I just picked up a max 2 and it is really grabby then it bites in I thought the bands are junk so the friction modifier might be all it needs ?

We had bought a machine that was very grabby also. Could not just slowly brake the bands. they would would just grab hard and lock tires up on that side. Come to find out there was no fluid in it at all. So make sure there is fluid in it at all..... And seeing as you just bought the machine it wouldnt hurt to change all the fluids anyways

[brian v]

That's just great so the bands are probley junk if there is no fluid on them I put a quart in but no difference