T.V. Vs. Kickdown

[DieselWarrior]

(Rig: '82 civilian K5 Blazer with 6.2l diesel, 700R4 and NP208)

My rig currently has a 700. I am *thinking* of replacing it with a TH350 or 400.

Before I do anything, I want to understand the operational differences of the TV and the kickdown cable.

I already understand the TV cable, I need information on the kickdown cable, and how it works....

I am wanting to get away from the OD trans and the PROBLEMATIC TV CABLE ADJUSTMENT, that if it is off, can toast your trans.

Mine is off, even after factory adjustment by the book, mashing on the pedal does NOT make the trans kick down a gear.

Further information, opinions and advice are welcomed!

Thanks,
Andrew

 

[DieselWarrior]

According to car-part.com, I can get a TH400 from a Suburban ('88 down) with a 6.2 and 4X4 for about $400 bones.

From what I can tell, the kickdown on a 400 is electric with a switch at the throttle linkage.

From what I can tell, the kickdown on a 350 is an actual cable, similar to the 700R4.

Please confirm my data. Id like to get the 400 trans.

I am *ASSUMING* the 400 will be a DIRECT BOLT IN to replace the 700, correct? Fabbing the kickdown switch, and the wiring will be no problem. Summit even has a switch kit for $50 if all else fails.

Thanks for your time,
Andrew

 

[DieselWarrior]

Yikes! Looks like the TH400 has a vacuum modulator, so Ill need to make sure the vacuum pump is working properly (I just installed a new one, but have not metered it yet...) and locate the proper VRV for it to work properly on my diesel.

Feedback?

Andrew

 

[diesel4me]

Yes,the vacuum modulator is important--on a TH350 you can just leave the detent cable dissconnected ,it wont hurt it,you wont get a forced downshift at higher speeds with it not hooked up however,but you can just pull the shifter down a gear manually instead...

The Th400 is electrically controlled as far as kickdown into a lower gear,and yes,irs a switch on the gas pedal that activates the solenoid inside the tranny's valve body that operates it...the vacuum modulator will allow a downshift to lower gears even if the switch or detent cable isn't working ,but at higher speeds the tranny wont downshift if the detent cable or switch is not working..

M '82 K2500 has a 6.2 TH400 in it--my VRV (vacuum regulator valve) for the modulator was not working right when I got the truck,and it refused to upshift until I was going almost 50 mph into third--and it shifted harshly too...I spoke with a tranny rebuilder and he said those switches were always a pain,and hard to adjust and keep working correctly--he advised my to run the vacuum hose to the modulator direct,right to the vaccuum pump,and to adjust the little screw inside the hose nipple on the modulator IN until it just touches bottom ,or slightly less...this will allow the line pressure to remain high enough not to let the clutches slip,yet still let the tranny upshift at a more "normal" speed and without slamming into gear..

So far since 1993 I have only put a few thousand road miles on the truck,but I have plowed at least 100 storms since then ,some very deep blizzards too,and my TH400 is still hanging tough...it shifts a bit "early" for my liking,but I was told a diesel tranny has the govenor set so it will do that on purpose,since the diesel's power curve is at a lower RPM than a gas engine..

Be aware a diesel automatic tranny has a lower stall speed torque converter with 6 bolts instead of the usual 3 bolt gas engined ones do--however I know a few guys whi just stabbed in a TH400 setup from a gas engined truck and just used the 3 bolts,so far they say it worked fine,and they hardly notice the stall speed difference..I like the lower stall speed myself,it makes the tranny feel a lot "tighter"..

 

[DieselWarrior]

Thanks for your time and effort to post all that data... Looks like I can bypass the VRV and the install will be easy as lard is greasy!

Andrew

 

[dremu]

I am *ASSUMING* the 400 will be a DIRECT BOLT IN to replace the 700, correct?

In short, no. The transmission's output shaft (aka tailshaft) must match your transfercase in both spline count and length.

See http://offroaddesign.com/catalog/doubler.htm (about halfway down in the "About the 203 rangebox" section.)

I suspect the easiest solution would be to get the transmission and transfercase as a matched pair.

You may also have to change crossmembers to mount the new transmission, and as the overall length will prolly change, you might have to change driveshafts (or at least get yours retubed.)

-- A

 

[DieselWarrior]

Okay, thanks much for the great information!

Andrew