Trans WOT shift @ 4000

[gc4x4]

My bone stock '87's auto trans shifts out of 1st and 2nd at 4,000 RPM on WOT shifts... engine will rev - in neutral - past 4,000 w/o any problem (only did it once)...

any thoughts where to begin looking? Linkage? Could there be something clogging an internal valve?

as always, thanks for your advice

[88GW]

That is the shift point on this particular setup. The kickdown will not have much if any effect on raising your shift points past 4000. The only thing I can think of is either installing a different torque converter or a shift kit.

[Bob Barry]

While your engine will rev over 4000rpm, the big question is whether it will actually be making more power over that point. A stock motor most certainly won't see much more on the power curve above that speed. A rough standard is to shift at the hp peak, so the next gear puts the engine right at the rpm of its torque peak.

[reddog]

Bob's point is (as always) a good one. Do you really want it to shift at a higher RPM. I think I may have misunderstood the post - thought it was hanging in gear on the upshift. If so then the info below stands... :rolleyes: Sounds like the adjustment of the modulator linkage on the drivers side of the carb. When I bought my 87 the return spring for the modulator linkage was gone and it would not upshift well. A spring and ajustment and all was well. I don't know it there is a write up in the tech section or not but I'd bet that if you do a search you would come up the the directions on how to adjust it.

Kerry

[ November 28, 2001: Message edited by: reddog ]

[Michael]

Kerry-
Are you talking about the kickdown linkage. It would help with that if your spring on the carb and the spring on the linkage were the same strength. If one is stronger or weaker than the other would cause it to shift early or late.

GC4x4- On the diffrence of the rpms that is normal. You have to imagine the load the rig has in neutral versus in drive. That is just normal power band. It is not pulling 4600lbs. You would have to get a larger converter and a shift kit to make it shift any later. Or what the heck manual shift that puppy. Mine does the same thing. I actually do not want mine over 4 grand. It has acceptable power at 3500 when offroading. Another way to get more power is to change out the cam. Everything else will follow. Just my .02 good luck.

[gc4x4]

Thanks for the responses... also, sorry about the fuzzy post... I just wanted to make sure nothing was seriously wrong or out of adjustment... it actually shifts, knock on wood, from gear-to-gear solidly and on the tach right at 4k every time... (please Jeep gods do not make the tranny fall out on the pavement now)... based on my experience in other vehicles, I just kind of expected it to rev a bit further before the upshift... and Michael, I agree, I'm OK with the 4 grand shift too

thanks for the responses

[reddog]

Michael,

I believe that linkage is for the modulation of the shift points. The 727 has no vacuum modulation like GM/Ford. Basically it feeds throttle position to the trans so the trans can adjust the hardness/timing of the shift. I am unsure how the kickdown happens with the 727. Maybe a combination of input shaft RPM and modulator position? I do know that if that lever is all the way forward because of no return spring the upshift points will be high and if you let off on the throttle the trans will not shift into third during "coast" at any speed. I believe the linkage is set up with the "slide" and a return spring so that it would not hold the throttle open if the trans linkage stuck.
I talked the PO of my 87 down in price because it was missing the return spring, shifted badly and he thought it needed tranny work. I did not tell him it was the missing $1 spring.

Kerry

[ November 28, 2001: Message edited by: reddog ]

[jeepbob]

The 4000 rpm kick down shift point would be correct for a 727ed FSJ. If your engines never see more than 3500 to 4000 rpm, how do you get thru the serious mud pits and up the big dunes? Some times you need the rpm to get wheel speed. Also while your engine may not make peak power at the higher rpm, it is not a huge loss until you either run out of spark, air flow, or float the valves. If you can keep the wheel speed up you not need as much hp to keep moving. I don't just hammer the throttle and hit the pit but I am not afraid to use it once I am in the pit. Ease in and throttle out.