Question for the Big Boys-FSJ's

[CutterN55]

Searched Jeep forums for an issue I have and havn't come up with anything. When I'm driving I have low top speed/high rpm. It's like I need a fourth gear. I have a 727 3 spd Auto tranny and have not done anything to it. When I lifted it, I also re-geared to 4:10's with 33x12.5 so ratios aren't an issue. I did rip out my emmissions system and built the top end of my 360 "pre-72" stlye. I put in a non EGR Performer E-brock manifold and 1406 E-brock carb. The new manifold moves the carb a little further forward but I've adjusted the crappy shifting linkage to account for that. Even still, incorrect shifting linkage would only throw off my shifting points and not my top end right? 3rd gear is third gear. I had the problem prior to re-gearing. I have no vacuum leaks and plugged everything not necessary. I have a vacuum source for my brake booster, 4x4 switch, vacuum advance, and PCV hooked up to the carb. My tranny is not vacuum activated. WTF right? I've built this the same way I've seen many done. Any ideas, I'm stumped. By the way, I'm not stuck in 4WD. What did I do and where did I go wrong?

[airforce26yrs]

What is your top speed and RPM with the gas pedal to the floor?


Take the block of wood out from under the gas pedal.

[rockready]

if it is the vehicle in the side picture then didnt they come auto 4wd and an emergency low.
does it shift hard
the other problem is you do not have overdrive in that tranny if it is a 3 speed. so high rpm is expected.

[theyeti1775]

if it is the vehicle in the side picture then didnt they come auto 4wd and an emergency low.
does it shift hard
the other problem is you do not have overdrive in that tranny if it is a 3 speed. so high rpm is expected.

That's my problem with the TH400 in mine as well.

Cutter did you ask over on IFSJA?

[CutterN55]

No Yeti, I haven't posted on IFSJA. So you have a similar problem huh? so it's probably not my tranny seeing you have the 400. Yours is vacuum shifted right? What kind of motor mods have you done?

[JavaTee]

Rockready hit it right, no overdrive. We've grown up with overdrive trannys, so we've trained our ears to hear the engine rpms lower. It happens to me all of the time, trying to shift the 4 speed tranny into 5th.
Later, T.J.

[CutterN55]

When I said high RPMs I meant like 55mph at 3K+. I can't take the freeway anymore. When I was stock I could go 80mph at about 3.2K-3.5K RPMs. I understand I should have lost a couple mph with the gearing/tires, but not 30 freakin' MPH. Even without OD, put your Auto in D2 and drive like that. that's the best way I can describe it....

[theyeti1775]

No Yeti, I haven't posted on IFSJA. So you have a similar problem huh? so it's probably not my tranny seeing you have the 400. Yours is vacuum shifted right? What kind of motor mods have you done?

Yep vacuum shifting.
Automatic 3 speed NO OVERDRIVE
No motor mods yet at all.
No gear mods either.

So at highway speeds the engine is screaming with RPMs.
Main reason I'm considering selling it.
To correct the factory stuff involves a bit of money.
For the price of fixing and getting it ready, I could have a fairly complete wheeler built with purchase of another vehicle.
Don't get me wrong, I love having a FSJ. It's up there with being a Marine for me. With the thin aftermarket for them, and custom everything being needed anymore it becomes a fianancial decision real quick.
With the Quadra-trac, lockers are up there with wheeling 37's hard on a Dana 35. It can be done, but it's going to bust sooner or later.

But far as the RPMs on yours, have you checked it's Timing (yours is still chain right?)? On my old XJ it would scream cause the timing was way off.
Sorry I ain't much help, just can tell ya what mine does. Around town it runs just fine. I try to avoid +45mph speeds with it. I'm pushing around 35's with 3.07's still.
You did just put a new carb on, do you have it tuned in just right? When I changed Carbs on the XJ it was a night & day difference in performance on the highway.

[CutterN55]

Yeah, timings good and carb is right in there. I'm wondering since I gutted the emissions if there is something else to the T-case as far as vacuum goes that could affect my range. I have the NP229 selec-trac. Everything works & shifts, but it's like I'm in really low ranges. When I shift into Four low, it goes lower(granny that will climb anything) and my 2HI drive ranges shift lower too, but I feel like I'm in low before shifting. I'm about to rip out this whole F-in drive train, I've got too much $$$ in this pig to stop now, but I'm ready to push it off a cliff....Mixed emotions.....

[JavaTee]

When was the last time your tranny fluid was flushed/serviced, and the filter changed? Also, could the torque converter be bad, or going bad?
Just some thoughts.
Later, T.J.