Retuning truck TH350 for hot rod

[roadmonster]

My car is running a TH350 from my old '71 C10 and I want it to shift more like a hot roadster and less like a firewood hauler. Truck had 3.08 gear and car is 3.00. Light throttle shifts at 15 and 25, heavy at something like 30 and 45.

I removed a TH350 of unknown history and it had lighter governor springs with stock weights. Both trannies shift well and I didn't notice any difference between it and the truck's, which has a known stock governor.

I have a governor kit with various weights and springs so my question is: Who has done this and which combination did you use?

My powerband is 800-4800, mild Comp cam ground for tall gear. Unknown converter is probably stock and seems to be 1600-1900 stall. New t/c is 2000-2300 so should get the revs up a little. I am thinking very light weights and medium-light springs for later shifts.

Any ideas?

 

[bobs66440]

I'm not sure about the trans, but with a mild cam and 3.00 gears in such a light car, you probably don't want a 2300 stall converter. The stock one will probably be better, imo. To be sure I would call TCI or someone similar with your specs and see what their recommendation is.

 

[roadmonster]

All converters stall lower in a light T. The stock one bites right when you slip it in gear and creeps unless you hold it. This is the next available stall over stock and true stall should be about 1900 or so. I have been through the research/recommendation process and believe this is the best choice. It's the JEGS Street Performance line and is very mild, just a notch above stock, which will translate to stock feel in my car. The stock one is always available to go back to, but I doubt that will happen. Stock is so tight RPMs drop at idle and 2nd gear chirps at 1800.

 

[bobs66440]

Sounds like you have it figured out. Let me know how you make out. I'll be dealing with that soon

 

[smokeyco75]

My uncle was a genious with automatic transmissions. When he built a th350 for me years ago he made it shift firm without a kit. I don't remember exactly what he did but I do remember he left a check ball out of the valve body and I think a spring was left out from behind the piston on the side of the trans. He used an adjustable governer and the tv cable to adjust shift points. I also remember him using something from a 700r4 in the internals. I want to say it was the intermediate drum for more clutches. I wish I could remember. I would ask him but he is no longer a part of the family. I wish I could be more help but it was a long time ago and I just can't remember.

 

[smokeyco75]

As far as stall speed goes my uncle told me recomendations on cam specs are based on an average weight car such as a camaro or chevelle. Go lower on stall speed for a lighter car and more stall on a heavier one. Keep in mind though more stall equals more heat generated according to him.

 

[roadmonster]

The only way to go lower on stall speed would be to use a TH400 converter (I have one) but it would creep so hard at idle you would have to stand on the brakes. The converter I got is the next one available over stock stall. I expect the slightly looser converter to act like a stock converter in my light car. There will be no additional heat because the stall is only about 400 rpm higher and it will be effectively hooked up at about 1800. I also have a 18,000 GVW cooler so heat is not an issue.

As for the governor, I believe the inner weights control the 1-2 shift and light weights result in a later shift. Outer weights control the 2-3 shift and the springs control the spread between them. So it seems light inner weights to take advantage of converter and tall gear to hold 1st longer, and med-heavy springs to keep 2-3 shift reasonable. I would like shifts at 30 and 50, with light-throttle shifts about 20 and 35.

I was hoping someone had already done this, but if not, I will follow up when the weather warms up with the results. Short shifting is a very common problem with Ts, so the info may prove useful.

 

[smokeyco75]

You are right about the shifting issues. I remember in high school meagreens c-cab would be in third gear in about sixty feet with the pedal to the floor. Assuming my memory is correct. That was twenty years ago lol.

 

[409T]

Search for torque converters or stall speed here and you should find a number of old threads discussing this. It seems to me that those who have tried numerous sizes of converters and many different stall speeds seem to gravitate toward 3000 - 3200 rpm stall speeds, myself included.

 

[roadmonster]

This thread is really about governor mods but keeps going back to converters. I've read the old threads. I know I have the right converter, it's the shift points I'm concerned with. With a 3.00 gear, most of my cruising is around 2000 rpm, and a high-stall converter would just be spinning and generating lots of heat. Even a stock converter will flash a couple hundred rpms at that speed and a 3000 would just be flailing.

Back to the governor, what I want is to hold off the 1-2 shift and leave the 2-3 pretty much alone. Down shift is perfect already, so I want to keep that. I like the quick hookup and 2nd gear chirp of a low-stall converter. So I'm thinking light weights and medium-heavyish springs and was hoping for feedback from someone who has tried it.

When this transmission was in my truck, I had a high-stall converter in it for a while and it was awful. I don't want the converter to wind up every time I accelerate. I just want some speed out of 1st gear.

 

[smokeyco75]

Try unhooking the vacumn hose to it. It worked on a ford transmission I had in a rod that was too tight for the kick down arm. Made it shift in the right spots instead of jumping through the gears.

 

[herrakani]

I used an adjustable modulator from ebay.

 

[roadmonster]

I've always used an adjustable modulator, but it only changes the shift point 2-4 mph. Governor recalibration is needed for any significant changes.

 

[Screaming Metal]

A little word of warning here....trying to GUESS what converter you need is gonna lead you down the road of dis-satisfaction here. While I have been doing all this mumbo-jumbo since Methusalim was young....Theres alot of the experience here on this site. You've already tapped the can by joining our merry little band of HotRod Crazies, theres more info you need to state for us to give you a good recommendation.
Weight and torque from a light car and a heavy car running the same motor and GEARS....well.... can be detrimental to the choice. Also tires....
We know what you have powerplant wise. We need to know roughly what gears your running, about what your gonna have so we can have a idea of the weight of the car, and what your driving habits are gonna be.
Setting the car up for a track is pretty easy. You know the power, you know the weight, you know the tires dia., you know the gears, you KNOW the distance, and you can basically get that car thru the lights within 300-500 rpm if little/no tirespin.

Nothing is more aggreviating than sitting at a redlight with both feet on your brake trying to keep it from creeping. The converter changes with the amount of torque the motor puts out. Your gears and tire size also has a effect on the overall equation. Also your 1st gear ratio....ie....a 700r w/Overdrive or a 5-speed, depends. If your running a 3 speed Turbo-Hydra 350 thats a diff. animal....
Its best to have too much stall speed than not enough....

 

[Screaming Metal]

Also, pulling hard against your brakes will induce alot of wear on your clutches, and brakes, also generating heat in the trans making your fluid life go down. Any performance trans needs a small cooler at least.

 

[roadmonster]

Transmission, rear end ratio, and cam were all specified in 1st post. Engine is 350 (I did not say). The TH350 I am using has had 3 converters in it: stock, high-stall B&M, and low-stall TH400. Stock converter works great, but it does torque up and creep in gear. Not a big deal. Otherwise, it is an excellent performer and good match for my setup. Going up a few hundred rpms in stall should let it idle freer, yet still run cool and have near-stock feel. I also mentioned I have a 18000 GVW plate-and-fin cooler, so heat is not an issue. Cam, heads, intake, and carb are all optimized to make the best of a tall rear end.

So, TH400 t/c is much too tight. Stock t/c is ok, but still tight. B&M is much too loose. I've had my foot in each one of these converters and know what they will do.

Car is about 1700 lbs and runs BFG T/A Radials 275/60 r15. It spins them easily with gas alone. I'm not trying to turn a dog into a good car, but a good car into a super car. The converter I have selected is the correct one for this application. I'm still looking for information about the original question (which was governor recalibration).

 

[Bugflipper]

The governor really doesn't have that much effect from my experience, I've been down that road myself. It's more for fine tuning. The only truck trans I have is in a 30 ford coupe that of coarse is a little heavier than a bucket. I went with the smallest weights in the B&M pack. The weights control your low throttle shifts. Stock is 16 gr the other two in the kit are 14 and 12. The springs in the kit control your med throttle shifts. Heavier increases the rpm it shifts at. I went with the heaviest spring. It still shifted too early after this for my liking. You may be able to move your low and mid throttle up 5 mph with light weights and heavy springs.

What really has the biggest impact is a shift valve spring. Lighter for quicker shifts, heavier for holding in gears longer. Car transmissions have a heavier spring, trucks use a lighter one. I think why you're not getting a whole lot of responses is a car th350 stays in gear a little too long for most people's taste. On a bucket it's about right. Most folks with normal weight cars want to decrease the time in each gear and if you buy a shift improver kit the shift valve spring is a lighter one for a truck that shifts out quicker. I think I ordered one on ebay for a car and stuck in it. Shifts out perfect now.

 

[roadmonster]

Heavy springs are causing the quick shifts. Instructions for TCI and B&M kits both say this. I am also holding the governor in my hand and can see how it works. Control pressure from the modulator holds the spool out to prevent the upshift. Outer weights fly out first, then compress springs (modulator pressure still holding), then inner weights finally overcome pressure and allow upshift. Heavy springs force early shifts. So the heavy spring works against the lighter weight so it doesn't change things much.

I have never heard anyone complain that a T stays in gear too long. Just the opposite, they are too eager to shift. I have a B&M shift improver kit in it, which most knowledgeable trans guys will say is junk compared to a Transgo shift kit. I will use the correct spring combo from the Transgo kit to further control the shift points. There is a lot of bad advice out there about leaving out accumulator springs, check balls, etc, which results in a hard shift but no other benefit and extra shock and pressure loads on the transmission. I will stick with Transgo instructions for internal valving and light governor weights with medium-weight springs to hold my full-throttle shifts while allowing normal part-throttle shifts.

350/350 combo is very common T setup and 1700 is normal weight. I was hoping someone would say "I used (x)weight + (x)springs and it worked great."

 

[Bugflipper]

Sorry meant to say light springs, been a couple of years since I did it. Went by the instructions.