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It depends...

what type of trans....

what type of "shift kit"?

There is only one brand of "Shift Kit" and it is produced and trademarked by TransGo.

A Transgo "Shift Kit" or SK is designed for professional trans builders to use in more or less stock applications to fix problem areas of the trans, prevent failures, and inform the builder of some of these as well as ome build tips.

TransGo also produces a "Reprogramming Kit" which is designed for hi-performance or heavy duty use. it will create firmer shifts, as well as fix some problems.

other companies make similar products. Superior makes a prevention type kit as well as a performance kit.

TCI, Art Carr, B&M, and others make "Improver kits".

Generally,
the hot rod type kits are used to firm up shifts.
Some do good things, others may cause parts breakage...

Most increase hydraulic pressure, for increased holding power.
Most require some drilling of the feed holes to firm up shifts.
Many have you block (totally or partially) accumulators that soften shifts AND control shift timing.
Some may dual feed clutches on certain transmissions, creating more holding power.
Some have you change shift valves springs.
Some give the option of manual control over downshifts and upshifts.
 

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All the TH350 kits will dual feed the directs, most will bump up the line pressure, and have you drill the feed holes or they will already be larger in a new plate.

I would use a TransGo reprogramming kit. With no other real mods I have Th350's taking 600 RWTQ.
 

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Re: sscamero,

red65mustang said:
for street wars, it's all about the rear gears, and jakeshoe needs to know your gears to assist you if your gona attempt a shift kit

a shift kit with high gears (2.8?) will make your car slower because the engine rpm drops to much when it shifts

you can get a screw adjustable vacuum modulator ($40? don't do Chevy) which allows you to adjust/change at what rpm it does shift to work with your gears (wish Ford had one!). Easy to swap/bolt in.

serious race car on a trailer....gotta have a shift kit

street car...as jakeshoe said, there is a risk the tranny will break
Gears have nothing to do with shift kit selection.
You will choose a shift kit base don your desires fro how hard a trans will shift, power output, etc..
A shift kit will NOT make your car slower under ANY circumstance if it is properly designed, rear gear or otherwise.
Engine RPM drop will be identical.
A trans with a 2.52 1st gear ratio, and a 1.52 2nd ratio will drop the same amount of rpm on a gear change, given the same variables such as converter.

a highway gear MAY cause the trans to feel like it shifts harder, as well as a tight converter, short sidewall tires. However it is a "feel" thing caused by the variables, not by the internal workings of the trans.

The main effect of a shift kit is to speed the apply of a clutch pack for a firmer feel.
Let's use a Th350 for an example.
When it shifts from 2nd to 3rd, it only has to apply the 3rd or direct cltuch pack.
The faster you apply, the firmer the shift is going to be.
Block the 2-3 accumulatorm dril the feed hole, and leave out all the cushion plates, and BANG, it will shift hard to 3rd.

Parts breakage is caused by an improperly calibrated kit, that bypasses critical shift timing controlled by the accumulators.
This is why you want to be sure your chosen kit doesn't cause harm.

Ever hear of a broken intermediate sprag in a TH350 or 400... that is caused by improper shift timing, or improper burnout technique.

Adjsutable modulators have little effect, and are mostly for part throttle shift control.


As stated,
A well designed kit will include mods to increase the life of the trans even in mild street applications. Such as dual feeding the direct clutches.
 

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there you go, jakeshoe

You answered his original question with that last post.

I agree, I was wrong to write "slower" with 2.8 gears.

I wrote a very brief post based on experience with Ford C-4's, it doesn't apply here.

Very clear you know you Chevy's
 

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I'll just make a couple pf points..

there are shift kits that do not dual feed the direct clutch of a t-350. TransGo sells a kit often refered to as " green box" kit... it's in a green box. LOL ... I've used hundreds of them in 4x4 trucks and other applications

There are adjustable vacuum modualtors for Ford products. You can also trim or add onto the pin length between the modulator and the valve it pushes on

In a C4 tranny shift calibration is important and so is the set up of the direct clutch pack. A C4 has the band coming off as the direct clutch is applied. A bind up can occur if the band and direct clutch are applied at the same time for a split second.


I recently changed the 2.79 gear in my 62 Falcon to a 4.11 gear. The car reacts much faster now , but the same RPM is used for shifting the full manual C4 behind the fire breathing 170 cid 6 cyclinder engine
 

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Re: there, I edited my first post

red65mustang said:
is everybody happy...

don't do Chevy's, I said that....

I would like to know where I can buy a screw adjustable modulator for a C-4 . (not a C-6)

==== screw in or push in modulator? What year C-4?

I have 4 at my house that fit the C-4.

mayb www.bulkpart.com lists them?



the vacuum hole....


 

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Crosley, thanks

for taking the time to post the pictures...and the prices on the link are great. Modulators listed don't say "adjustable", where did you buy yours.

What I've got right now is a push in yellow band on a 7?' case with a "C" ratio servo and Red Eagle clutches and band. (was going to try a red band/different spring next)

Basically I want an adjustable to do more testing. By shimming back the stock modulator it behaves "pretty good" with my motor/carb combo for shift points.

C-4 question if I can. Irratating, doesn't down shift to first until the car is almost at a full stop, mild acceleration from stop with 3.5 gears/14Hg shifts to second at ? 1200 rpm/to soon. Suggestions?
 

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I buy parts from trany supply houses for a few decades.

if your mod is a yellow stripe unit, it should have threads in the end of the hose bib.... mayb not.

You could try a green stripe unit, lengthen the pin about .050 to see if that helps or hurt.

I use welding rod to build new pins for the C4 & C6
 

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Crosley, thanks

For $10 it's worth a try (and I'll have a spare O ring and modulator)

looked it up, yellow push in is 7/17/72 forward.

thanks again

odd, the link site doesn't list the red band

humor?, I'm gona swap to a C-6 so I can have a pink or purple band, my grand daughters favorite colors, drive a tranny shop nuts, paint it both colors.....
 
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