tranny dont shift right at all.

[idontlikechevy81]

so i have a 1981 chevy with a turbo 350 and i just put a tranny in it.well when i i shift from second to 3rd it seems to shift fine for like a second then it just bogs way down. and wont it kick it self backout unless i get going like 60. could this be a kickdown cable problem because i dont think its adjusted right. and when your slowing dowing it jugs bad when its trying to downshift itself. its hard to explain i guess what it does its really weird idk! any ideas will be helpfull. thanks!!

zack

[___Brandon]

Does it have a turbo 350 with the locking torque convertor?

I used have an 83 that did the same thing. I would have to hold in second with the shifter until I wound it up to about 60 and then shift to drive. It would then shift to third and the convertor would lock like you are saying, but by then I'd be going fast enough that it didn't matter.

I never did look into fixing it, I just dealt with it. I always figured it was something to do with the lockup though.

[j cAT]

Originally Posted by idontlikechevy81

so i have a 1981 chevy with a turbo 350 and i just put a tranny in it.well when i i shift from second to 3rd it seems to shift fine for like a second then it just bogs way down. and wont it kick it self backout unless i get going like 60. could this be a kickdown cable problem because i dont think its adjusted right. and when your slowing dowing it jugs bad when its trying to downshift itself. its hard to explain i guess what it does its really weird idk! any ideas will be helpfull. thanks!!

zack

explain what speed does the tranny shift at? 1-2 ? 2-3 ?

CHECK THAT THE DETENT CABLE IS INSTALLED CORRECTLY ?

WAS THE TH350 THE ORIginal transmission that you replaced.

if this is bogging down I would check the timing also the EGR .

you have a 350 cu engine ?

[idontlikechevy81]

Originally Posted by ___Brandon

Does it have a turbo 350 with the locking torque convertor?

I used have an 83 that did the same thing. I would have to hold in second with the shifter until I wound it up to about 60 and then shift to drive. It would then shift to third and the convertor would lock like you are saying, but by then I'd be going fast enough that it didn't matter.

I never did look into fixing it, I just dealt with it. I always figured it was something to do with the lockup though.

im not sure what ya mean about the locking tourque converter. this is exactly what i have to do is hold in second till bout 40-50 then shift into drive. but trying to get up hills is a pain in the a**. and i think the timing is a little bit off but not bad. if this was the timing why would it just do it at them speeds. and as in detent cable do you mean kickdown?

[j cAT]

Originally Posted by idontlikechevy81

im not sure what ya mean about the locking tourque converter. this is exactly what i have to do is hold in second till bout 40-50 then shift into drive. but trying to get up hills is a pain in the a**. and i think the timing is a little bit off but not bad. if this was the timing why would it just do it at them speeds. and as in detent cable do you mean kickdown?

the torque converter locks up at 42MPH. this causes less slippage with in the transmission. with a tach you will see about 200 rpm drop when this occurs.

can you answer my questions on what the vehicle has for engine, and operation ? If not then you will not get any answers that will help you resolve your issues.

[idontlikechevy81]

400 small block

[j cAT]

Originally Posted by idontlikechevy81

400 small block

so this is a 1981 chevy what ? with a 400cu engine . th-350transmission . well slowly your giving some details. what about a complete description ?

[j cAT]

Originally Posted by idontlikechevy81

400 small block

with the 400cu engine my guess is this is some hack vehicle.

A VEHICLE PUT TOGETHER WITH VARIOUS PARTS FROM MANY DIFFERENT VEHICLES /YEARS.

MY guess this is a pontiac 400cu . if so the timing should be 16DEG tdc. also 93 octane fuel 4barrel carb.

my guess is the detent cable along with the timing or even the wrong plugs would all add up to your many issues.

with a repair manual you can adjust this cable easy. the connection to the carb must be at the correct point. the cable must move freely. the cable is secured at the intake manifold. this is where the D push button is located. you push this D button the pull this cable toward the firewall fully. then release the D button. then you manually move the throttle to WOT. YOU WILL SEE THIS CABLEAND HEAR THE CLICKING ..this is now set.

If you did know what your doing you can tweek this adjustment one click each way to get what you want on the down shift MPH/throttle pedal position.

best not have to floor it to get the tranny to down shift. 3/4 down is best.

then we have the vacuum line to the transmission which also controls shift points..the vac modulator ...

[idontlikechevy81]

its a 81 chevy silverado silverado c10 the motor is out of a 72 caprice. wheen i bought the truck the everything was fine with the tranny then it went out. so put another one in it. i checked the vacuum line. i bought the tranny used and the kickdown cable came with it so i guess what asking is how to adjust it and what is the detent cable?

[silicon212]

Originally Posted by idontlikechevy81

its a 81 chevy silverado silverado c10 the motor is out of a 72 caprice. wheen i bought the truck the everything was fine with the tranny then it went out. so put another one in it. i checked the vacuum line. i bought the tranny used and the kickdown cable came with it so i guess what asking is how to adjust it and what is the detent cable?

The detent cable is what you are calling a 'kickdown cable'. You want to adjust this so that a 3/4 throttle 3-2 downshift occurs around 30-40 MPH, and a WOT 3-2 downshift occurs no higher than 70MPH.

This transmission has a vacuum modulator on it, so make sure that #1, your engine is in tune (if it's not, stop here and tune it up or forget about it working right), and #2 you have a vacuum line running intake vacuum to the modulator.

At part throttle, 1-2 upshift should occur around 10 MPH and the 2-3 upshift should occur around 20MPH. These are the low speeds where the shifts should take place - engine load and vehicle speed will determine where shift points occur from there. There is a screw on the inside of the vacuum nipple on the modulator that you can adjust to fine-tune the shift points. Modulators are available pretuned for certain uses (red-band, black-band etc). It doesn't so much fine tune where shift points occur as much as it affects how the clutches apply - firm or soft. Adjusting the screw can 'crispen up' or 'slush out' the shift points.

Changes in the speeds of shift points will require modification of the governor, and this is generally done through replacing the flyweights with different value parts. If the transmission came out of a car with a tall axle ratio, and went into a vehicle with a shorter axle ratio, then you're going to want to perform these modifications, else the shift points will not be where they need to be.

Edited to add the following: A locking converter is standard on the 1981 version of the TH350. This transmission is referred to as a TH350C - the C denotes lockup. If there are any wires that plug into the transmission, it has a locking converter. The locking converter has a clutch inside it that locks the impeller and turbine in the converter together when engaged, negating any loss through the torque converter. At this point, the engine crankshaft is solidly driving the input shaft of the transmission as the torque converter is essentially removed. On these older vehicles (anything that uses a TV cable or vacuum modulator), there's a sudden drop in RPM when it engages, this could be mistaken for the engine bogging down. The amount of RPM drop really depends on the stall speed of the converter - if you're under hard acceleration and it engages, the RPM drop will exactly correspond to the stall speed of the converter. Not good for acceleration, which is why it should never lock under hard acceleration.

[j cAT]

Originally Posted by idontlikechevy81

its a 81 chevy silverado silverado c10 the motor is out of a 72 caprice. wheen i bought the truck the everything was fine with the tranny then it went out. so put another one in it. i checked the vacuum line. i bought the tranny used and the kickdown cable came with it so i guess what asking is how to adjust it and what is the detent cable?

well now you have the method to adjust this detent/downshift cable in post #9 .

since this is a 1972 chevrolet 400cu . the fuel will be 93 octane. then adjust the timing to around 10 deg BTC.

I will see if I have the specs on that year engine still around here.

I had a 1967 400cu the timing was around 7.5deg tdc.

what about the distributor ? you have an ignitor kit that replaced the points ?

also buy a vacuum guage. check vacuum and repair all leaks/replace all cracked hoses. these usually fail right at the carb. if the carb is not OEM improper vac ports may be used to the vehicles vac system. also the detent cable may not be on the correct pin.

vac leaks will reduce the ability of the engine to suck fuel out of the carb . this will cause bogging down. imprper timing also reduces vac.

with the leaks fixed and the timing correct I always got 17-20 inches of vac. the needle was not moving. steady..

[j cAT]

Originally Posted by idontlikechevy81

400 small block

this may be a 1971 or older chevrolet 400cu. 1971 is the last year this was used with my records..in the caprice.

the timing is 8deg btdc.

[silicon212]

Originally Posted by j cAT

this may be a 1971 or older chevrolet 400cu. 1971 is the last year this was used with my records..in the caprice.

the timing is 8deg btdc.

Negative - the 400 was available in the Impala / Caprice from 1970 (first year SBC 400) through 1976.

[j cAT]

Originally Posted by silicon212

Negative - the 400 was available in the Impala / Caprice from 1970 (first year SBC 400) through 1976.

looking up this 400cu engine for the caprice on an internet search , it agrees with your quote.

my records however do not list the engine after 1971. so I don't have what the specs would be.. like timing .

you have that so he can adjust it ?

[silicon212]

Originally Posted by j cAT

looking up this 400cu engine for the caprice on an internet search , it agrees with your quote.

my records however do not list the engine after 1971. so I don't have what the specs would be.. like timing .

you have that so he can adjust it ?

Nope, none of that is going to matter in this application. Remember that the factory recommended settings are a compromise between operating in all kinds of environments, from Alaska permafrost to Phoenix sunshine and broiling eggs on the sidewalk, and apply generally to the vehicle they're used on. Sticking to the factory recommended specs, likewise, present a 'no-fault' baseline for a mechanic to use - whose going to argue against factory specifications, anyway?

The intuitive mechanic will realize that no two vehicles are exactly alike, even two 1972 Caprices (for the record, I've owned two 1972 Impalas, so I kind of know about these cars - though they both had 350s in them). Therefore, the intuitive mechanic will tailor each car's specifics pertaining to actual real world operating behaviors. S/He will use the proper equipment to ensure each engine is operating to *its* maximum potential - and the 'safe bet' factory settings may or may not play out.

In the case of the OP's vehicle, I would drive it under the conditions the driver will encounter, and after it is fully heated up, tune it so that it's as advanced as possible without encountering detonation (spark knock). If the OP is using the original E4ME carburetor and C3-controlled distributor, upgrading the C3 computer (and possibly the wiring harness, using junkyard sourced components) will allow the engine timing to run as aggressive as possible without encountering said detonation. The OP can use the 350 PROM, there does not need to be a specific "400" PROM. For a more aggressive spark curve, a 305 PROM will also work. The one iffy part of this is that I am not sure there is a 400 specific knock sensor.

If the C3 system is indeed in use here, a baseline timing of 8 degrees BTC would be appropriate. It can then be fine-tuned as necessary.