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Difference between 86 928S and 86.5 Kickdown Relay?
I've got an early 86. In my Fusebox R&R, I found that I had the kickdown relay for an 86.5, not the part number referenced on 928gt.com's relay specifications for an 86.
Are these relays different enough that my kickdown wouldn't engage? Currently, it will downshift from 4-3rd, but I'm not sure I've ever even seen 1st gear in the 928. It starts off a bit sluggish and never really has a neck pulling downshift. At 60-70, a press to the floor downshifts, but not two gears.
I can download one of the accelerometer programs for the iphone if it helps diagnose. I also believe I may have some other parts on the engine not behaving for optimal performance. I'm planning the intake rebuild in the next month or so.
Thanks in advance for the responses, you guys are great!
I saw this yesterday, but I know very little about the autos so I didn't chime in. For the shifting, there's some combination of using 3-2-3 or something that will enable you to start off in 1st gear and then manually shift as you like if everything is working properly. I just tried searching and couldn't find anything about it right away.
I do know that one of the vacuum lines coming off of the 7-way splitter (in the valley under the airbox) goes all the way back to the tranny in an auto and if this is leaking vacuum it can cause problems with shifting.
There are lots of other things to check like cables and stuff, but if you know you need a top end refresh I'd just figure on doing that first, and verifying that your engine is running and idling good. Once that's the case and you know your vacuum lines are good you can move on to the tranny.
My 86.5 auto starts in first from a stop...(another reason 86.5 rules!)
If I floor it at 70 she kicks down immediately and engages the hyper drive... Shifts at over 100 pulling like mad. Am not foolish enough on the street to know if it shifts again or just keeps pulling to redline!
Check at the crank in front of engine for the throttle rod/accelerator cable and make sure it is adjusted to give WOT and that the kickdown cabe is adjusted correctly at this point also.
Get in a quiet spot next to a wall. Engine off, but ignition switch on, transmission in Drive. Windows down. Slowly press the throttle to the floor while listening for a click from the transmission solenoid. If you hear the click, the transmission should kick down. If you don't hear the click, pull the kickdown relay and install a temporary jumper between 30 and 87. Repeat the check. If you now hear a click, the relay is the problem.
The function of the kickdown relay is to make the transmission upshift instantly and positively at redline. The relay gets a signal from the EZK ECU (up to '86) or the tachometer ('87-up) which opens the relay contacts. This drops the solenoid to the non-kickdown position, causing the transmission to upshift, avoiding over-speeding the engine.
As soon as the transmission shifts, the high-RPM signal is gone, so the relay closes again, clicking the solenoid back to the kickdown position, holding the transmission in the current gear until you let up on the throttle or the engine hits redline again.
I was having similar problems with my 85, but the problem was in the pedal lever, it was not adj enough, so it was barely touching the kickdown swicth. Fix that yesterday, goodbye good MPG , if you can have someone press the pedal at the same time you are at the back of the car (trans area), if the kickdown is fuctioning propertly you will hear a click.
From the PICS posted only diff on the right most two, the far right they added a Diode, most likely for isolation (back feeding) of the circuit.
I do know the later cars (89 up?) included a Fuel Injection cut out circuit, that looks at the CPS so if the frequency is < less than(?) idle(?) not sure how it works but a bad one will cause a no-start or intermittent start. So when Kick-down switch is closed, it cuts out the Fuel injection signal so you can Clear Out the cylinders if flooded.
Like holding down the gas peddle on a carbureted engine.
I do not believe the older Autos do this.
I have been troubleshooting no kickdown on my 86.5 and I think it is the kickdown solenoid. Could someone point me to the part number on that bad boy? Cannot find it at Pelican, etc..
Jeff: I see this is post is number 1 for you, welcome. If you go to the New Visitor thread and scroll down to post 45 you can download PET for your M/Y. That 4-page thread has a ton of information.
09-08-2009, 03:38 PM
Difference between 86 928S and 86.5 Kickdown Relay?
, if you can have someone press the pedal at the same time you are at the back of the car (trans area), if the kickdown is fuctioning propertly you will hear a click.
PET
