First of all, do all TH400 transmissions have electronic kickdown?? Including the BOP TH400. Second question, how would someone hook up the kickdown when installing a TH400 in a vehicle that didn't originally have a TH400?? Third question, is there any differences between the BOP and Chevy TH400 other than the bellhousing?? Is the BOP TH400 just as strong as the Chevy TH400? Thanks in advance.

 

Youll have to excuse me here I dont know what a BOP is, but all the TH400's use an electric kickdown. B&M sells a kit that attaches to the carb linkage for $45 part# 20297. You TH400 will upshift without this but it wont down shift. If your planning on putting this in a 3rd gen your going to have to get this TQ arm adaptor pt #30299, or you could halfass a support like I had in my car.

SSC

 

Internally they are all roughly the same. BOP just have a different bellhousing bolt pattern. Caddy uses the same pattern. There are a few dual bolt pattern housings out there also.

There are actually more bellhousing bolt patterns than just GM. Jag used TH400's as well as a couple of other cars.

There are a few internal differences between TH400's over the years. Buy the book on how to rebuild one first. Early versions have the good direct clutch hub that you can put the 34 element sprag on but the later trannys have some of the design flaws fixed from the factory.

Sorry I can't offer any suggestions for the kickdown. I believe SSC covered it all. I use a manual valve body so I have no kickdown or automatic features in mine.

 

BOP = Buick Olds Pontiac ... they have a different bellhousing bolt pattern because the Buick Olds and Pontiac blocks have a different bolt pattern for the tranny. Also, it's the same bolt pattern for all 3 so most people and parts stores refer to it as a BOP transmission. You can use a BOP tranny with a Chevy block and vice versa but you have to buy the adapter plate in order to do so. (BTW, my TH400 is going in an '82 S-10 not my thirdgen)

Just curious, does that valve body make it so you HAVE to manually shift through the gears like a standard transmission just w/out a clutch? Seems kind of annoying if that were the case... what's the advantage? I've heard of a manual-automatic valve body but I never did understand how that worked.

 

Manually shifting an automatic is nothing like shifting a manual transmission with a clutch. It's not recommended for street use at all because of how it's designed.

My manual valve body also uses a transbrake and is reverse shift pattern. PRN123

When installing a manual valve body the tranny is modified to eliminate all the automatic features. If I pull the shifter down to 3, I can start off in third gear. The oil accumulators are eliminated so the shifting from gear to gear is sharp with no delays (very annoying for street use) The front intermediate band is removed. This is part of the automatic features and allows engine braking in 1st and 2nd gears. The governor is also removed since it controls shift points in the automatic feature.

What you have left is an automatic transmission that will hold all gears to any rpm. When you shift, there is no delay or cushioning when the next gear engages making very harsh shifts. There is only engine braking in high gear. When you slow down in 1st or 2nd, the tranny just freewheels and doesn't let the engine slow the vehicle down.

Manual valve bodies are used in drag and circle track racing and are not really needed for street use. Having to shift every gear gets annoying real fast. You can easily burn out a tranny by starting off in 2nd or 3rd gear too much.

The transbrake part of my valve body engages 3rd gear at the same time as I'm in first. This prevents any power from going out the back of the tranny and I don't need the brakes to hold back the engine. I can then bring the engine rpm up to the converters stall. When I release the transbrake, the fluid holding 3rd gear is dumped and the car launches at a very high rpm. It's also very violent on driveline parts. That's why I went to a 9", 3 x .083" driveshaft and 1350 series u-joints. My torque converter currently stalls at 4900 rpm (using the transbrake)

Instead of using a manual valve body in a street car it's better to just install a shift kit. You can still manually shift the gears and hold each gear to any rpm but when you put the tranny in D you still have the full automatic features. The shift kits can also be easily changed. If you installed a stage 1 kit and want more aggressive shifts, you pull it out and install a stage 2 or 3 kit. Most kits come with multiple versions of how you want the tranny to shift.

Another thing to do for firmer shifts is to completely drain the tranny and torque converter and use Type F fluid. Dexron tranny oil slips too much and gives granny shifts.

 

Kinda like when I rev my engine to 5500 rpms in low 1 and shift, I get no delay or cushioning. But you get this throughout the whole rpm range. Better invest in a neck brace. :P

My friend had his 700R4 rebuilt by a machine shop and took it back to them probably 4 times in 1 month because he wanted it to shift harder. I don't know what they did to it this last time but every time the car shifts from 1st to 2nd even when not manual shifting, the wheels spin, the back end jerks left, and you practically get your neck ripped off. He had to misadjust the TV cable on purpose to keep it from shifting so hard because he eventually got tired of the hard shifting.

And this doesn't hurt the transmission??

 

Ron Sessions wrote a great book on T400's. All the info for the book is on my page.

When I installed my T400, I went with a standard valve body with out a kick down cable. I also installed the BM Pro Ratchet shifter. Hence, if you want to drop down a gear, just bang the lever

Miles

 

No. It's just another type of tranny oil. Although they are designed to be compatible, don't mix them. That's why I mentioned draining the torque converter also. It holds about a quart or so of oil. Both fluids do the same job as a tranny oil. The difference is that Type F oil has a higher static friction value than Dexron. It just means the clutches won't slip as much and the shifts will be firmer. Slipping clutches cause wear.

Stock transmissions wear out from overheating, lack of fluid changes (should be every 2-3 years) and slipping clutches. Putting in a simple shift kit to firm up the shifts will make the clutches last longer. Abuse in any transmission can cause failures of the hard parts also. Don't expect an old tired tranny to last with just a shift kit. Take the time to replace the seals and clutches at the same time. Rebuilding an automatic transmission isn't very hard but plan on a day or 2 if you've never done one before. I've actually had my tranny out and disassembled a couple of times now since I put it in last fall. A couple of simple mistakes I had to correct. The TH400 is a much nicer tranny to build than a TH350.

The Ron Sessions book is "the" book to get if you plan on rebuilding a TH400.

 

Thanks guys. I'll definitely be taking a trip to Barnes & Nobles soon to take a look at Rons book.

 

Among other things, I would recommend staying away from the Type F oil. Even Ford stopped using it way back in '76. If you've been around long enough (like me) to have worked on vehicles that used that stuff you would know that it is not good. It can not handle heat and turns into a stinky varnish. Also, an extremely harsh shift is not good for your tranny or performance.

I will gladly debate this with anyone.

 

dont know if you typed it wrong or you have some weird transbrake i dont know about but every transbrake i've ever helped install at the shop holds the tranny in FIRST and REVERSE, not third gear

thats why to go in reverse you have to shift it to reverse and then hit the transbrake button to apply the clutches

 

Powerglides use first and reverse. Turbo trannys use first and third. It's how they're designed internally.

Mine is a Turbo Action transbrake. When in first gear only the forward clutches are applied. Activating the transbrake applies pressure to the direct drum clutches. The only way to be in reverse is to have the direct drum and rear band applied.

Edited hours later:

I was thinking about it all day. It's possible it does go into reverse. Reverse in a TH400 has the direct drum clutches and reverse band applied. The valve body could be supplying fluid pressure to the reverse band also but there's no way of telling. The TH400 only has one pressure port for checking oil pressure.

The only way to tell is to see if the car goes into reverse or forward when the transbrake is applied but I don't think it will work since the tranny has to be in first gear for the transbrake pressure to work. (The way the manual valve works). I don't have to hit the transbrake to go into reverse. I just shift to reverse and it works.

Either way, it locks the transmission so that there's no output. As long as it works, I'm happy.