Transmission Jumps from Drive Into Neutral

[ZJP]

Hi, I recently purchased a early 70's vintage Max II with a new Vanguard 16hp V-Twin engine. The problem I'm having is the transmission jumping/shifting into neutral while I'm driving it. As you can imagine, I loose all steering and control until it stops and I can shift it back into drive. Is there a simple fix for this like some kind of linkage adjustment or does this sound like bigger problems? I'm not much of a mechanic and any suggestions would be appreciated.

[mark m.]

It sounds like the detent spring(s) that holds it in gear are either missing or it (they) has disintigrated.

[ZJP]

Hi Mark, Thanks for the quick reply to my posting. Not sure what a detent spring looks like, is it inside the transmission or somewhere on the outside of it? - John

[hydromike]

The detent spring is inside the transmission; it fits within the shifting collar, and over the output shaft on each side of the transmission. They basically look like a coiled spring that has had its ends joined to form a circle. Over time, they can get stretched out, they can break, and the shifting action of the transmission isn't a very "positive" action any longer; less of a THUNK-THUNK, and more of a thumpthump. Replacing them requires an almost complete tear-down of the transmission.

I'll try to find you a picture....

EDIT:: Okay, not the best picture, but this should begin to help out. I pulled this from the T-20 rebuild article availble on the Site. The detent spring is located in the shift collar that's being held in the picture.



~m

[micmac]

Here is what they look like out of the T-20

[kunzmm137]

I would check the linkage before tearing apart the tranny. My hustler did not want to stay in reverse, and it ended up being bent linkage. I realize that the setup is different on a max, but it is worth a look.

[duckhunt81]

I will second what kunzman137 said. You very well could have a bent linkage which is not rotating the diamond shifter enough, thus not engaging the transmission completly. I would check the rod that runs from the shifting lever back to the diamond looking thing on your trans.

[ZJP]

Thanks everyone for the helpful advice. I'll start by checking the linkage and work my way up from there if necessary. I'll let you know what I find....if anything. - John

[ZJP]

Transmission jumps from drive to neutral

Hi, I placed this Post in the regular Max Forum but will try here as well in case there are different opinions about my problem. I recently purchased a early 70's vintage Max II with a new Vanguard 16hp V-Twin engine. The problem I'm having is the transmission is jumping/shifting into neutral while I'm driving it. As you can imagine, I loose all steering and control until it stops or hits something and only then I can shift it back into drive. Is there a simple fix for this like low on trans fluid or some kind of linkage adjustment or does this sound like bigger problems? I'm not much of a mechanic and any suggestions would be appreciated.

[6X6]

FIRST: Make sure it's engaging FULLY into drive. You need to open up the machine and see if the diamond shifters are moving all the way forward till the corner gets right next to the case, if theres much of a gap at all check your linkage to see what's stopping it. If you keep trying and grinding it WILL wear out the shifter teeth if that's not the issue to begin with.
SECOND: If the diamonds move fully in each direction, you'll have to remove them to see if a shift pin is worn. (Pin is on bottom of the shifter in the tranny. If the pin is worn flat it won't fully engage) Dowel pin should be round and not worn down, though be aware early T-20s used T shaped pins. If you have em, replace em, It's cheap to do and those T-pins break more easily. (Been there done that)
IF all checks out then it could be the teeth themselves. If the teeth on the shifter are worn it will do that too.
Use this as a reference, though hopefully you don't need to actually open up the tranny. http://www.6x6world.com/forums/conte...kid-steer.html

[ZJP]

Hi Johnny, thanks for the annalysis annd suggestion. I've checked the diamonds and they're in the right position when engaged in drive so I guess the problem could be deeper like the pins or teeth (ugh!). - John

[6X6]

Hi Johnny, thanks for the annalysis annd suggestion. I've checked the diamonds and they're in the right position when engaged in drive so I guess the problem could be deeper like the pins or teeth (ugh!). - John

Well, before you get too worried, check the pins (#2). Don't know how buried the T-20 is in a maxII, but at least you don't have to open the tranny to check. Just pull out the shifters, should be covered in the Rebuild link I posted. I see there was another thread, I forgot about the detent spring cause that hasn't been an issue for me, YET. (something to look forward too? )
HOPEFULLY you have worn pins that keep the shifter from fully engaging, their cheap and easy, which is always good

[ZJP]

Hi Johnny, I replied several days ago but for some reason it's not showing up on the posting but regardless, thanks for the suggestions. I'm pretty sure it's not the linkeage so I'll check the pins next. I'm not real good at this stuff so if it's anything more complicated than that, I'll have to pay someone to fix it. I'll try to look it up somewhere but is it easy to check the pins? Do they just pull out or is there more to it? - John

[Mike]

ZJP, if you will look in the How-To section of the site, there is a rebuild article for the T20. It will let you see how easy it is to remove the diamond shifters. Two bolts to remove a cover plate that holds the shifters in place and then you can just pull it out.

[ZJP]

Thanks Guys, I'll run with your helpful suggestions and hopefully fix the problem. It's still pretty cold up here in the northwoods of Wisconsin and my garage isn't heated so I think I'll wait a few weeks before I start banging my numb hands against cold metal. Thanks again to everyone. - John