I recently bought a new 700r4 from tciauto which came shipped with a vacuum lockup switch. The transmission will be mated with L98 in an 89 iroc.

Do I have to install this switch?

Can I use the stock switch - the one which was used with the original transmission? Will it lockup?

If not how do I connect the vacuum switch, i.e. where do I connect the pressure hose?

 

I have used both. The factory switch and the aftermarket switch perform the same function (allowing the TCC to unlock when you are accelerating briskly) and are installed in the circuit (both electrically and vacuum-wise) the same way.
IIRC, the TCI part might be adjustable and offers some tune-ability but I found the factory switch worked best.
Only one is needed along with the factory brake light switch.

 

Skinny

thank you for your response

I called tci and they were pretty firm in insisting that I use their vacuum switch claiming that their transmission is designed to work with this switch providing independent function of the lock up. They suggested I connect the vacuum switch to carburettor and when I mentioned that this is a TPI setup they told me to hook it up to manifold. Any thoughts on that? My concern is that I don't want to ruin a brand new gearbox from the start, not to mention that I paid a heap for it (2500$ with the converter).

regards
i.

 

Their switch or the one you have, other than perhaps the set point, are the same functionally. Using the TCI part will keep them happy so you've nothing to lose really. Go with theirs.
Hooking it up to manifold vacuum is the same for either switch and the same for TPI or carb. .

 

OK

Thanks

I shall pass this on to my guys at the shop.

regards
i.

 

Took a quick look online and saw that the TCI switch is adjustable. Once installed you can change the point where the TCC unlocks (via a small set screw) by how much and how quickly you open the throttle. It can be a little tricky but misadjustment won't hurt anything.
A word of caution, be absolutely sure you have the throttle cable adjusted correctly. Failing to do that will cook your transmission.

 

Ok

I will keep this in mind. Thank you for your sage advice.

regards
i.