Just converted my K5 from Tbi to carb/Hei. I have it running fine but need to know if my mods will effect torque converter lockup. I don't see the vac switch on the firewall like my 1984 K20 with 700r4 had. Anyone familiar with this?
CK5
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How is 700r4 lockup done on a 1988 Blazer
- Thread starter 5akman
- Start date
All TBI trucks had lockup controlled by the ECM. Since you've down-graded the truck you'll have to retrofit in the vacuum and brake switches and wiring and this still won't be as good as either factory configuration. The later transmissions are simpler and don't have the hydraulic controls over lockup, so you'll be dependent on having a good electrical setup. Those transmissions can lock in any gear at any speed. The aftermarket solutions aren't perfect either, but you could look and weigh your options. You might want to use a pressure switch on one or more of the test ports on the tranny.
I rebuilt this rig sans as much electrical as I could since its going to just work off the beach in Alaska launching my commercial fishing skiffs. My 1990 TBI Dodge gives me nothing but grief as all the electrical gets messed up by the salt water environment.
I just need this lock up to work for the 3000 mile drive next month from CA to AK. After it arrives in AK, it will be off road use only and probably not more than 50 total miles per summer of use.
I'll look into an electrical system. Something like this perhaps: https://www.ebay.com/itm/700-R4-3rd...rentrq:9b531cb41690aa48031c7a76fffc5634|iid:1
I just need this lock up to work for the 3000 mile drive next month from CA to AK. After it arrives in AK, it will be off road use only and probably not more than 50 total miles per summer of use.
I'll look into an electrical system. Something like this perhaps: https://www.ebay.com/itm/700-R4-3rd...rentrq:9b531cb41690aa48031c7a76fffc5634|iid:1
I wouldn't want a latching relay setup for a street driven rig, but it might be good enough for your one-way trip. Keep in mind the limitations. if you coast down in speed without using the brake pedal it can stall the engine. If you forget to push the button and cruise in overdrive you can overheat the trans. Better than a simple toggle switch, but takes away from the idea of "automatic" transmission.
I agree
I have the Edelbrock 700r4 bracket on the throttle lever and have done the measurements to get the throttle/TV cable anchor bracket located correctly. I think I'm good and will be test driving this weekend to verify. Supposed to upshift from 1-2 at 17-20 mph correct?
Yes. Something like this would work: https://www.summitracing.com/parts/...SsqW36iMUkV7SdqPOWaKcUuQ2MyDiHdBoCiCIQAvD_BwE
but you could also just buy a pressure switch and source the rest from pick-n-pull or maybe eBay.
I didn't know this was available, but appealing option: https://www.ebay.com/itm/Adjustable...982828&hash=item2cc98a0b87:g:4MYAAOxygo9Q56gk
but you could also just buy a pressure switch and source the rest from pick-n-pull or maybe eBay.
I didn't know this was available, but appealing option: https://www.ebay.com/itm/Adjustable...982828&hash=item2cc98a0b87:g:4MYAAOxygo9Q56gk
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As long a you can feel the torque converter locking up when you flip the switch, just run it that way. I have 2 old trucks that are set up that way and they have been fine for years. It isn't a perfect set-up like a factory installation, but I can lock it in in 2nd, 3rd and 4th with mine. It even holds when I let off of the gas and push on the brake. If you forget to turn the switch off, it let's you know when you slow down. It will buck a little before it downshifts to 1st and unlocks. But if you have the carb tuned well, no big problem. Both of mine have shift kits, too. I don't recommend flipping the switch to lock when you are on the gas hard, like 3/4 throttle or more. I feel that it's hard on the converter clutch. Just my opinion.
But I will admit that it hurts a little to know that you are going to sacrifice a K5 to the salt water disease... but they can't all live forever!
But I will admit that it hurts a little to know that you are going to sacrifice a K5 to the salt water disease... but they can't all live forever!
http://www.bowtieoverdrives.com/catalog/catalog_inc/viewitem.php?ITEMID=332
I have used this kit. Switch allows the convertor to lock up in 4th gear, and disengage when brake is applied
I have used this kit. Switch allows the convertor to lock up in 4th gear, and disengage when brake is applied
I ended up buying two different kits off of ebay. One used two relays and I never could get it to work and received limited help from the seller. The other kit I bought required dropping the pan but it was a real easy install and just gives lock up in 4th. I ran it through a toggle switch so I can turn it off if the road conditions warrant it.
