What modifications needed?

[Lo cash lester]

What do I have to modify to use the wider 091 first gear on a type 1 trans? I installed it in Lo' Cash John's trans and had problems staying in first. Switched it for a regular SB 1st and all is good. Wanting to use it on my new street car trans, any help would be greatly appriciated.

[Guest]

The overall height of the 091 idler is about 0.035" more than the normal idler, so you need to surface grind the synchro side to fit. I can't remember how much I took off, but I did grind it a few times until it was set up on the tight side.

[kcr]

The 1/2 slider needs to be narrowed.A stock 091 1/2 slider measures .940 in width,surface grind yours to match.A stock post 66 slider measures .980.Ive ground the synchro side before too,but i think the correct way is to take the material off the pinion bearing side.i thought it was like .019.

[Henryhoehandle]

The best way is to use an 091 slider. The teeth on the inside of the 1st/2nd slider are longer then the type 1. When you grind (or machine) material off of the type 1 slider, this will allow it to engage deep enough, HOWEVER, the detents in the shift rail need to be further apart because the slider will not travel enough to get BOTH 1st and 2nd. If you have it in a jig then you can see what I am talking about. I have seen people just machine the slider and get away with it, but you will not get much engagement by doing that way.... and most likely will start popping out of 1st or 2nd in a short while. The 091 slider does mate to the late reverse idler of the type 1, so IMO, the best way to do this is use an 091 slider..

Eric

[locashguest]

Let me clarify, I'm using the complete 091 gear, syncro and slider. When I set it up on the jig it looked good. Installed in the car it would enguage first but would pop out with acceleration. I reset it twice with the same results . Thanks for the help!

[Henryhoehandle]

Then I would examine the 091 first gear closely and look for worn edges on the side of the teeth. If the taper is worn very much at all, then that will cause it to pop out....

Eric

[Casting Timmy]

The best way is to use an 091 slider. The teeth on the inside of the 1st/2nd slider are longer then the type 1. When you grind (or machine) material off of the type 1 slider, this will allow it to engage deep enough, HOWEVER, the detents in the shift rail need to be further apart because the slider will not travel enough to get BOTH 1st and 2nd. If you have it in a jig then you can see what I am talking about. I have seen people just machine the slider and get away with it, but you will not get much engagement by doing that way.... and most likely will start popping out of 1st or 2nd in a short while. The 091 slider does mate to the late reverse idler of the type 1, so IMO, the best way to do this is use an 091 slider..

Eric

I'm trying to investigate this more as I seen multiple ways people say to do it. Are you narrowing the gear any?

I ask as someone I talked to recently said they do the conversion by machining .014" off the big pinion bearing side and then you have to use an 091 slider. He's always very insistent that an 091 slider must be used with factory 091 gears. Aftermarket gears you can use the narrowed T1 sliders and he takes .040" off the first gear side.

I'm wondering if the difference of the conversions is in machining the gear narrower and using the no line hub second comes closer and detent remachining isn't needed. If the machining is done on the pinion side you should get more gear overlap as well, I always wonder how much stronger first could be if the factory main shaft had first backwards a little bit.

I have used my mill as a measuring device and found out the slider mates about .035" higher with the 091 idler vs the 002 idler, so the slider being narrowed .040" seems to make the difference correct with that. I assume shimming for an unmachined 091 ilder will make the detents to need to be farther apart, but machining the 091 idler down in thickness keeps second gear closer and the detents work out with the late shift rail ????

[Casting Timmy]

Learned something new, you can put the 091 main shaft into a T1 if you modify the 091 main shaft. I know a guy in the UK that does it and will show me his drawing for modifying it when he goes to his machine shop and gets a copy. Basically it looks like he has the 4th gear race ground down to the diameter of the 4th gear area on a 113 shaft while at the same time getting the end threaded for the stock VW nut.

Basically think of turning the 091 main shaft to look like a Weddle hybrid main shaft in my opinion. Or maybe think about it like the guys that turn down super beetle main shafts to go into a 113 main shaft box, except he leaves the splines on the shaft.

I wonder what 091 main shaft supply is like in different areas of the world. Sometimes they seem kind of scarce over here.