T5 - new seals, speedo drive gear, etc.

[oz]

Greetings,
I have my T5 out of my car to change my clutch. I want to replace seals and change the speedo drive gear (if it's an easy job).

It looks like it has a slow leak between the tailshaft housing and the main body of the transmission. How hard a job is it to replace this seal?
I have 3.73 rear gears and my speedo driven gear keeps getting chewed up and my speedometer is off 10% so I'd like to change the speedo driven gear too.

I don't think my rear seal is leaking but I'll change it for good measure anyway.

Is there anything else I need to check, replace, upgrade while I have the transmission out?

My input shaft looks good but I'll check the diameter. How much undersize is acceptable?

Thanks!

 

[need4spd90]

ok, fun stuff

there is no actual seal between the tail housing and the gear box, it just uses a bead of RTV..i prefer Ultra Black...

to change the speedo drive gear on the output shaft, you need to remove the tailhousing. Aside from the bolts on the outside, you need to remove the offset shift block, inside the shifter hole on the tailhousing..to do this, get a hammer & punch, then drive the roll pin all the way thru..wiggle the block till it comes off the shaft, being careful not to lose the pin, or the ball and spring thats underneath the block..then the tailhousing can be removed, and the speedo drive gear can be swapped out...order a new clip for the gear as well..you dont want it to lose tension and have the gear slide down the shaft after its all been re-assembled..been there done that..

re-assembly is great buckets of fun..you have to get the ball&spring into place under the block, slide the tailhousing and shift block into place at the same time while not messing up your bead of RTV on the gearbox

Put some grease in the "H" pattern and in the locations where the ball detents. I use the red wheel bearing grease for this. Petroleum Jelly works too. Put the ball in the middle detent closest to the "H" pattern of the detent plate. The grease will hold it in place. Slide the tail on, but stop 1/2 - 3/4 inch short. Put the tip of the spring in the block, leaving most of it out. Hold this from the side with your finger. Touch the spring on top of the ball, press the block down over the spring until the ball is forced inside the block and hold it there. Guide the tail housing a little further on until the block is against the shift rail. Wiggle the rear tip of the block up and down to help it get started as you push the tail housing closer. Once the block is on the shift rail, force the block further on until the ball is now detenting in the neutral slot. Seat the tail housing and torque it. Clean excess RTV with solvent, position the block on the shift rail so the pin aligns and drive it into place.

as for the speedo gear itself, i'd order the black 6 tooth gear along with the proper sized driven gear(yellow i think?, dont remember)..this is what i run on mine..the yellow 7T driven gear can go no "deeper" than 3.73's, so if you ever decide to run a 4.10 or something, the yellow gear is no good past 3.73..the black 6T gear starts at 3,73 and allows for accurate correction up 4.30 ring&pinion

 

[oz]

need4speed90,
Thanks for the detailed explanation! After reading that, I'm not sure if I want to try that or not...

 

[need4spd90]

its not as bad as it sounds on paper..its no real picnic either tho lol