998 Slipping in 3rd High Speed Modded Kickdown Linkage

[Beaverseagle]

Hello All,

My bird: 82 sx4 248 automatic transmission 998 75k.  As far as I know the tranny has never been rebuilt.  2 inch lift with 235 tires.

So I've converted to DYI kickdown due to my TBI conversion. I have metal rod connected directly from my throttle to the kickdown lever. I have it set up so that the lever is completely closed at idle. As I accelerator the kickdown valves opens.  At WOT the kick down valve is completely open.   Here is what I'm experiencing.

When I select 2 on my auto shift selector the car drives great. It accelerates great! The shift from 1 to 2 is smooth  But obviously I can't drive at higher speeds in 2.

But when I'm in D, the up shift from 1 to 2 is not smooth.  When she drops into 3rd at 40 she dogs out.  She doesn't seem to be able to down shift from 3 to 2 for passing between 45 and 65. I read that at 70 the tranny will not downshift. She's also has very slow acceleration from 40 to 60.  Very hard to maintain 65 in windy conditions.  When I'm in traffic and have a wind break she has no problem maintaining 65 and cruises easy up to 85 mph.  This makes high speed travel (65 to 70) on open highways very difficult.

I've adjusted both the front and rear bands.  I have changed the tranny fluid and filter.

I'm not sold that the clutch discs are bad. I've performed the stall test and she passes.  I'm thinking my throttle/kick down linkage needs adjusting or maybe the torque converter is bad or not performing as it should.

I have no experience with auto transmissions and looking for some guidance.  I'm think also since the linkage has been modded..my trans fluid pressure could be off and causing the discs to slip at high speed.

Thanks for your help

[eaglefreek]

Did it have 235's before the TBI conversion? What is your axles' gear ratio. The throttle valve rod, not kickdown, is connected to a bellcrank from the factory. Is your rod still connected to this bellcrrank? Are you sure that the way you have it connected now, that the rod is moving in the same direction it is supposed to?

[macdude443]

To add to that, at WOT the lever at the trans should be all the way towards the back of the car, then return back via spring tension to the full forward position at idle.  It may have a lock-up torque converter problem?  That'll kick in around 35-40 in 3rd.  I also wonder what the gear ratio is.  My '82 SX/4 with the same transmission slipped pretty bad going into 3rd in Drive and it needed a rebuild.  When I changed the filter there was a pile of crap stuck to the magnet.

[Beaverseagle]

Did it have 235's before the TBI conversion? What is your axles' gear ratio. The throttle valve rod, not kickdown, is connected to a bellcrank from the factory. Is your rod still connected to this bellcrrank? Are you sure that the way you have it connected now, that the rod is moving in the same direction it is supposed to?

I did convert to the 235's  before the TBI conversion.  I did take one road trip with my old carb after I put the 235's on and I did have the same issues.  Which I thought was a fuel problem and is one of the reasons I went with TBI.   I have completely removed the stock kick down setup.  I have a solid rod that goes directly to the tranny.  And yes I have confirmed...the tranny valve open by pushing towards the rear of the car.

[Beaverseagle]

To add to that, at WOT the lever at the trans should be all the way towards the back of the car, then return back via spring tension to the full forward position at idle.  It may have a lock-up torque converter problem?  That'll kick in around 35-40 in 3rd.  I also wonder what the gear ratio is.  My '82 SX/4 with the same transmission slipped pretty bad going into 3rd in Drive and it needed a rebuild.  When I changed the filter there was a pile of crap stuck to the magnet.

So how the new setup works is the rod is connected to the same lever the throttle cable is on the throttle body. The throttle body has a very strong return spring that closes the both the throttle and kickdown rod.

The rebuild seems to have solved your problem, correct?  My feeling is if I replace the TC, I might as well rebuild the tranny. I heard pulling the tranny is the hardest part of the rebuild.  I didn't have much crud in my tranny filter, so I was hoping the clutch plates were find. But it's sounding like I'm going to need to bite the bullet.

[macdude443]

The rebuild solved my slipping for sure.  I've played with the stock kickdown adjustment and made the shifts harder and softer but it's never slipped just by playing with the adjustment on a good transmission.  Before the rebuild, I could keep it in 2 and then let off the gas a little and shift into D.  It would shift fine then.  Under load 2 to 3 though, it would always "flare up".  When the rebuild was done, I had the shop disable the lockup via the valve body.  It hasn't been enabled for a few years now so I don't even remember much about how it felt.

[Baskinator4]

Do you know if the kickdown is acheiving 1:1 ratio with the accelerator cable? For 1 inch of accelerator movement you should have one inch of movement at the transmission lever. I'm curious if the forward position is not correct- while at idle or little pedal pressure. I just put a Bouchillon kickdown cable on mine a week ago and I found that there is a lot of travel at the lever on the transmission until it actually engages the pump.

[Beaverseagle]

I was wondering the same thing.  There is a lot of play.  The adjustment procedure has you put a spring on the lever that pulls it completely forward while the adjustment is made. My assumption is that the lever needs to be completely forward while the car is at idle.

Also my kickdown rod does move the lever on the tranny through the entire range of travel. At some point, I expect the tranny to kick down.  It does not, I usually will manually shift the tranny to second if needed on the highway. I make sure this is not done above 60 mph. 

I'm planning a rebuild for the transmission and hope it resolves the issue.

[mudkicker715]

It is not a kick down rod at all. It adjusts hydo to the tranny to stop slippage, which in turn makes happy clutches.

Not certain how it chooses a passing gear.

Misadjustment on that rod is obviously a bad thing for the clutches.

[Beaverseagle]

I was able to adjust the modded kickdown linkage. She's shifting much better and able to keep her speed up. Still having a issue with steep hills. She doesn't kick down from 3 to 2. But she accelerates better. I adjusted the starting point about  .25 inches from the stop.

Getting ready for a rebuild.