Transmission

We have a TH400 in our ride and was wondering if anyone has done overdrive in theirs. I do not want to change the tunnel so is there a conversion for the tail of the trans or another trans with the same size configurations?? Thank you.

Look up Gear Vendors Overdrive. They sell kits that bolt on to your transmission in place of the tailshaft housing. I believe the kits use a version of the Laycock overdrive units that originally came in the Healey.

They are strong enough that they have been used in very fast street driven drag cars. The kits can be set up to split gears. In other words, you can turn your 3 speed T400 into a pseudo 6 speed. Or you can set it to shift into OD in high gear similar to a regular OD transmission.

The downsides are mainly price and driveshaft length. The kits are as expensive as a brand new transmission. Somewhere in the $2500-$4000 range depending on how the kit is configured. If you are not comfortable with transmission work, you might need to find someone to install it. The current transmission crossmember does not have to be moved (I think).

Also, the unit adds a good bit of length to the transmission, so the driveshaft will have to be shortened. Measure carefully before you buy a GV's unit, since you may not have enough room for a decent length driveshaft on a Sebring with the longer transmission.

Also, I'm pretty sure the GV's unit can be installed without removing the transmission. Since it fits in the narrowest portion of the trans tunnel, you would aslo need to measure for width fitment.