Tackling the not accurate speedo that eventually went non functional in my car and ran into some problems and could use some advise from those more experienced. First its a BOP TH350 and the drive gear on the tail shaft that was on the car when i got it split and now after all this time I took the opportunity to go ahead and get the right gear combo for an accurate speedo. First thing i noticed was that the replacement drive gear from tci did not use the wide 7/16 clip, it used the narrower 7/16. TCI says this was and it did go in place no problem and I put the yoke cup on but I dont know if i got it in the right spot. there isnt a lot of area for it and it almost looks like it should slip up under the drive gear but since its my first time and the previous gear split I dont know where the cup and gear sat in relation to each other. Anyway I button it all up and I have a working speedo again but only for about 15 miles then dead. I pull tail housing off to discover the clip for the drive gear broke right at the little tab that goes in the hole in the shaft. I even made sure I got the right driven gear like the cover said (36,37,38,39) and I got a 39 driven gear. So im getting stumped already and need a some experienced help. What could have broken the clip? and how do I install the yoke cup correctly. The manual says nothing on correct depth or it's distance in relationship to the drive gear, or even if it should be slipping under it.
The yolk cup with the Oring on the inside at the end is the last thing on the tail shaft . the driveshaft yolk should slightly like an inch go in it. . That is if your yolk has splines all the way to the end of it. If yolk has an inch or two at the end with no splines then you should have a grove at the end of the tail shaft for an o ring. The cup is the last thing you install on the shaft. The clip you put in the hole on shaft , and then you push down on the clip to slide the gear over it. The clip will pop up partially ounce the gear is positioned far enough up the shaft, this is the part of the clip that you had to push down to get the gear over the clip. The number on the cover that matches the gear you line up with the dot or notch on the tail housing. That is the critical part. That is the number on the gear that is in the cover. You have a 39, so if you line up the spedo gear housing with the notch on the tail shaft to any other number besides 39, it will be too tight. That will usually work until something gives to heat or friction. Too loose and it wont work at all, or very erratic. If there are 2 holes for the clip i am pretty sure it goes on the furthest hole up the shaft. With the tail housing installed the gear on the shaft should line up in the middle of the housing hole.
Thanks for the info it got me thinking in a new directions I think I understand more of what is going on plus some new parts arrived and shed some light on this situation. - the red 17 tooth drive gear I ordered from tci was too loose on the output shaft. the 18 tooth I ordered (because I realized I got the ratio wrong the first time) fits the shaft snug and is technically correct. The technically part is that the original grean 18 tooth gear has one side of the inside seating area larger to accommodate the flange from the yoke cup so it slips right under/inside the drive gear. from the looks of the shaft this is needed because when the gear is on and clipped there is less that 1/4 inch for the yoke cup to seat behind the drive gear before the shaft splines start. the groove gives it a lot more area to fully seat the yoke cup flange on the shaft. - Other versions of the th350 and what seems to be all 700r4's ? dont look like they use a yoke cup if the drive shaft yoke does not have a weep hole ( since the cup would have kept the fluid out of the yolk anyways) So anyways I come to the conclusion I broke the clip cause I must have had the yoke cup flange up against the non grooved style gear because I remember that kinda loose red drive gear not being quite so loose when I put the cup on. so as I drove the cup prob expanded and pushed the gear forward enough to break the clip. I found someone had a NOS original grooved 18 tooth green on Ebay like my original and Ill give that a whirl. If I somehow mess that up the previous owner put a Olds 12 bolt with 3.08s under the car and it seems he used the drive shaft from the other car as well as I saw no weep hole in the yoke. So I can then use the 18 tooth non grooved blue that TCI sent me that does fit snug (still don't know why the red and blue wear different when they both are said to fit the same applications per TCI) and not use the yoke cup to stay rolling.
I see I described a 350 C spedo housing. You have the skinny one with a slot for the metal piece slide in and bolt to hold it. The yolk cup you have there is for a slip yolk. It would slip under the oring. If yours has no hole it will not leak. dont use the slip yolk cup. If you take the gear that the cable goes in , and stick it in the housing it goes into check to see if it wiggles, moves up and down, It should not. If you go to a transmission shop they will give you one for next to nuthin. and a clip , and the drive gear housing, with the seal, the whole thing. The yolk should slip into the cup . if not , toss the cup.
It's working like a charm, hot dog I got a working speedo again and it's accurate! I definitly needed someone to bounce some experience back my way to help me figure out what I was looking at and what my options were. Thanks for the help Rivi !
Ended up tossing the cup because I couldn't get a hold of the stock style gear with the inside groove for it. Luckily I already had that yoke without the weephole and could just change over with minimal effort.
