RngTrtl

Dear All (see sig for car),

I cannot get 1st gear to hold past about 4.5k rpm under WOT. I have searched through the forum and gotten some info that alludes to my problem, but nothing definitive. The vacuum on the tranny is good I think b/c it shifts smooth under light throttle and firm under hard throttle. The Bowden cable that runs from the throttle linkage to the tranny is tight. So what is left? The odd thing is that it will hold 2nd to redline and then shift to 3rd. Never have had enough street to hold 3rd long enough to see if it shifts at redline to 4th.
Any and all thoughts would be greatly appreciated. Take care.

David L. Lutz

Did you check your fluid level?

RngTrtl

Yup, Fluid level is perfect.

Bill Ball

Yeah, mine shifts out of first at 5200 or so. Second will bounce off the rev limiter.

I haven't bothered to study this. Fiddle with the Bowden cable some more.

RngTrtl

Am I correct to assume that tighter should make it shift later, or the other way around?

Pfunde

I had a simular problem with my other OB 3 speed zf 15 year's ago. But that came out to be to low oil-presure. I think it's suposed to be like 4.0 bar, and it's very easy to adjust.

RngTrtl

By oil pressure, do you mean tranny oil pressure? If so, how does that affect the shifting and how would I adjust it?

Bill Ball

In the 4-speed A-28, the modulator pressure does not affect shift points, just firmness. There is a full throttle control pressure shiftpoint adjustment screw on the valve body. The Bowden cable - tighter upshifts later.

SeanR

I had the same problem but fixed it with ensuring my vac system was air tight, and adjusting my bowden cable several turns. After the bowden cable adjustment, 1st goes all the way to redline in 1st.

Also ensure your gas pedal is making contact with the kick down switch when you push it all the way down. By hitting that switch with the pedal, it will ensure you go all the way up on the RPM's.

RngTrtl

Thanks for all the advice. I will tighten up the bowden cable a few turns and see if that does it. If not, I will look into the valvebody. Is this a sound way to go about trying to get what I want. 1st do the cable, then try the screw. Or should I do it the other way around?
Thanks

SeanR

Make sure your cable moves easy, now that I think about my last post. I'd start looking at the cable 1st, pedal 2nd. If you had no vac to the system, it would shift real ****ty and you would notice it.

IcemanG17

I drove a 1990 that would shift out of 1st at about 5500......mine will hold to at least 6k....typically redline at 6200 in every gear......BUT if you are not 100% floored with the gas it will shift sooner....typically 4500-5000 or so

SeanR

I'm guessing it's because of the kick down switch. The gas pedal has about a dozen different adjustments that can be done. Well, at least 3 different spots to adjust at the bottom of the pedal. My kick down didn't click until I took the pedal from the furthest back to the middle position.

Ang's '90 is different, so YMMV.

Mrmerlin

make sure that first the throttle is opening all the way you will need a helper to do this, then adjust the bowden cable so there is just a bit of slack not much, if it is already close then you dont need to do full turns try going in half turn incriments,takewrench with you , so you can pull over and make on the spot adjustments, make sure to pull well off the road while your doing the adjustments, no need to take a chance of getting hit

Bill Ball

Use the cable adjustment. The screw on the valve body was just mentioned for information more than anything, but if you have the book on the A28, it's described in there.