What's new
By:
Filters

700R4- FMRVB vs Shift kit auto

SteerAndStuff

SteerAndStuff

Red Skull Member
Joined
Dec 29, 2020
Member Number
3204
Messages
188
Loc
Wyoming
Have been wheeling a th400 with a FMRVB for the last handful years. New rig will use a 700R4 and I am considering keeping it an automatic. Have ready mixed reviews about the tci constant pressure VB. New engine will be drive by wire so can only figure to hook up a TV cable to the throttle pedal. Obviously the 700 doesn't have a great track record for strength, which way would keep the 700 alive the best? I'm not opposed to a FMRVB again if it helps on consistent clutch engagement and much simpler setup w/o a TV cable.
 
I like 700R4’s. They can be built plenty tough. Even a th400 is a massive pos till they are properly built. i have used the TCI constant pressure valve bodies in 700R4’s and like them. No problem with them as far as I’m concerned. I won’t touch a TV cable ever again. I don’t think that a reverse shift pattern valve body exists for a 700R4. Even they did I wouldn’t use one though. I race in a vehicle with a RMVB TH400 and it seemed like a good idea before actually using one.

Most t-cases shift best with the trans in neutral and vehicle still rolling. With a forward shift, it doesn’t matter if you have to go from first past 3rd to get to neutral. It does matter having to go from 3rd in low to shift past 1st on your way to neutral. You pretty have to bring the rig to a stop. Having used both forward and reversed shift patterns I’ll never use a reverse pattern again.

Edit: In my forward shift rigs I can shift from low to high without slowing down and with no grinding of gears. In the race car with reverse pattern you have to come to nearly a complete stop to get the trans into neutral to shift the t-case.
 
Last edited:
I've never had trouble shifting from low-high or back in my fmrvb th400. Found if going from high to low slip case into neutral, downshift 1 gear in tranny, then slip case back into low while rev matching rpm to ground speed. Driven plenty of non-syncro truck transmissions, it essentially same concept. Pretty much reverse order from low to high.

Do you have your TV cable still hooked to a throttle body with your constant pressure VB?
 
SteerAndStuff said:
I've never had trouble shifting from low-high or back in my fmrvb th400. Found if going from high to low slip case into neutral, downshift 1 gear in tranny, then slip case back into low while rev matching rpm to ground speed. Driven plenty of non-syncro truck transmissions, it essentially same concept. Pretty much reverse order from low to high.

Do you have your TV cable still hooked to a throttle body with your constant pressure VB?
Click to expand...

No, getting rid of the TV cable is the whole point of using the constant pressure valve body. You just plug the hole in the trans forget that those nightmares even exist.

Our race car has an all billet n 300M internals FMRVB TH400 behind a 700 hp 455 cid small block. We run a hero 3 speed which shifts like butter compared to the atlas we used to run. When shifting to low range from high it’s always to slow down so trans is coming out of first gear into neutral anyway, once trans is in neutral the main case shifts to low no problem. (Synchronized t-case) When shifting from low to high it’s because we’re needing to speed up because we ran out of gear and rpm.

Even If you put the t-case in neutral first then shift the trans from 3rd to 2nd to 1st to neutral it still hurts the trans. We even tried no trans compression braking for this reason. Our trans shifts instantly too, so you can’t slap it from the 3rd to neutral fast enough that it doesn’t engage 1st gear as soon as the indicator hits first. With a reverse pattern there’s no way to go from low to high without slowing down to the vehicle of first in low. Where as I can shift my shift my rock crawler from low to high at 25 mph without touching the brakes.

For a trail of course it doesn’t matter, take all the time you need. In the race car it’s a problem that cost valuable time.
 
From my reading the full manual valve body no longer needs a TV cable, obviously, but the constant pressure still uses one to adjust shift points:

STEP 26. With the adjustment complete, road test. With moderate acceleration your transmission should shift: 1st to 2nd .......... 15-20MPH 2nd to 3rd .......... 25-30MPH 3rd to 4th ........... 40-45MPH If the throttle Valve Cable is not adjusted properly, the transmission will shift into 1st, 2nd, and 3rd within seconds of acceleration. DO NOT CONTINUE TO DRIVE VEHICLE IF THIS HAPPENS. Readjust cable. If you continue to have problems, please contact TCI®’s tech department for assistance.
Click to expand...

as found here: https://static.summitracing.com/global/images/instructions/tci-376021.pdf
 
You must log in or register to reply here.
Top Back Refresh