700r4 2-3 flairing

[kustomwerker]

i know you guys are 200 guys, and i got some really useful advice on the one i put in my camaro, but this one`s on a 700...i have an 88 chev 3500 with a 350 and originally a th400...problem was the th400 sucked on the highway...i converted it to a 700r4 with the correct dsshaft and ecm, and was very happy with the performance gain on the highway,BUT it flaired on the 2-3 shift...this conserned me, so i did some pressure tests, and a local tranny guy told me they sounded fine...i then installed a b&m shift kit..i pulled the accumulator housing and found both springs were broken..i thought "ahaaaaa", but was wrong...(the shift kit replaces the springs with spacers) now the tranny shifted hard into 2nd, and improved 2-3 shift, but still flaired...just not as bad...shortly thereafter, i blew up the pump...(broke at the dogs where they engage the converter) so i replaced it with an on the shelf unit i had kicking around, and no more probs...i`m gonna fix the 1st trans, because i like having a spare around, and this one looks to have been rebuilt fairly recently, but i want to rectify the probla=em at the same time...could it be a leaky servo at the shaft, or seal???any help is realy appreciated...

 

[Blazer406]

Been there... done that with a 700R4.....

Most of the time.... a stock corvette servo is all that is needed. I had a stock (non-vette) servo that flared... I tried everything.... someone finally suggested the corvette piece.... I put it in.... with tranny still in my S10 Blazer (I had a 400 hp 350 in it).... It was tight getting it to go by the body...

First time I drove it... it was like "WOW!" major difference on the 2-3 flare.

There are some larger "billet" servos... that even provide more pressure.... but in most cases that is probably not needed unless you have lots of HP....

I've seen vette servos go in the $30 - $50 range new on the web.....

HTH

 

[Alky V6]

Third gear in the 700 is a clutch pack. It is called the 3-4 clutch pack. The 2-4 servo also acts as the accumulator for that clutch pack. As you probably already guessed, that clutch pack is used for 3rd and 4th gear. Accumulator piston guide pin bores are important with this unit to control shift quality. There are a couple aftermarket 3-4 clutch packs on the market. Use one of them.

If you want to see the results of a 700 used for high performance use, I have a page on my website dedicated to the carnage.

 

[kustomwerker]

so use the clutch pack, or the new servo, or servo with a new guidepin donnie???and thanks for the response blazer...i planned on doing the servo regardless, but that just reaffirms my thoughts...

 

[Alky V6]

For the vehicle it's going in, I would either go with the large V8 size servo with a good shift kit or the corvette servo. The problem with the corvette servo is, you will end up with an aggressive 1-2 shift. Some people get tired of it very quickly.

 

[kustomwerker]

the 400 that came out was like that...built by dynamic, and would snap your neck into every gear...i dont mind much, and will probably be the last owner of the truck anyway...thanks a lot for all of the advice...

 

[Alky V6]

Just be aware that there are a lot of tranny men that do not recommend banging shifts with a 700. Accumulated metal fatigue problems is the reason. As I mentioned earlier, check out the page on my site for some good pictures of metal fatigue problems with the 700. Ugly stuff.

 

[Blazer406]

For the vehicle it's going in, I would either go with the large V8 size servo with a good shift kit or the corvette servo. The problem with the corvette servo is, you will end up with an aggressive 1-2 shift. Some people get tired of it very quickly.

I am not a transmission expert... but I had my 700R4 out of that V8 S10 about 10 times over a year and a half period... I think I broke anything that could be broken by a 400 HP V8. With that said.... IMHO.... the corvette servo is a good chioce... it eliminated my 2-3 flair. Later in further mods... one of the shift kits completely blocked off the 1-2 accumulator (read shift softener) completely...... this combined with the billet servo I was running at the time..... did snap your neck.... It would rattle the dash when it shifted if you weren't on the gas enough to bark second.... that and I was running a 9-1/2" vigilante converter locked after it went into second.

Anyway... if you don't block the accumulator off... and run the corvette servo... IMHO... it is a good compromise.... no flair.... and snappy but not unliveable hard shifts.... It was just fine.

Donnie is right... if you get the shifts too hard... I'm sure the tranny won't like it... and it is a pain to live with.... I have an old roomate that still fuses about the time I spilled coffee all over him when I was just easing along and the truck shifted into second so hard it spilled all over him...

 

[Alky V6]

You should not have a flair 2-3 shift no matter what servo size you use. If the servo is too small, you will get a soft shift. Not a flair shift. A flair shift on the 2-3 indicates cross leaks or broken stuff (springs for example). It can also indicate a weak (starting to go out) 3-4 clutch pack. The corvette servo only masks other things going wrong in the unit, along with the added fatigue load on the other components.

 

[kustomwerker]

broken springs where???crossleaks at the servo around the shaft???where should i look for the crossleak...the 3rd gear is solid once i`m in it...no slipping once in gear...theres no band material in the pan, and no signs of metal in the pan or filter...broken springs where???in the clutch pack???i did find broken springs in the accumulator housing when i put in the shift kit...

 

[Alky V6]

The main things that I have seen that affect the 2-3 shift are;
2-4 servo travel
3-4 clutch pack clearance
Sealing ring damage on the input shaft. Usually, caused by bad stator bushing(s).
Servo piston pin bore wear is usually not a problem with the 700.
Check all accumulator piston pin bores for wear. There should be a slip fit clearance only. Any rocking of the accumulator pistons on their pins is a crossleak and a big no no.
Last but not least. The quality of the 2-4 band and the 3-4 clutch pack friction material. Any glazing of these friction elements will greatly affect the syncronized timing of the 2-3 shift. The friction elements can be slightly burnt and not leave any debris in the pan.
Any problems that can affect line pressure. Worn TV boost valves, plugged filter, worn out pump.