My wife's '89 700R4 developed a nasty "banging" (I'm pretty sure the clutches are slipping) in low gear. It happens when starting from a dead stop. The harder the gas, the more the bang (or slip). Other than that, it operates quite normally. It has 116K miles.

On a limited budget, a rebuilt 700R4 is out of the question, local auto stores even want $1000.

I have a 700R4 with 134K that I "was told" works, but I never saw it run, so I can assume it needs a rebuild.

I've heard the poor man's shift kit for the 700R4 is the low/reverse boost valve, and the servo, both can be changed with the unit in the car. If I buy just these, maybe (perhaps a long shot) I'll get some more clutch pressure in low & buy some time for me to learn how to rebuild the other 700R4 in my garage??

The Transgo Kit for the 700R4, everyone speaks highly of, the picture I saw on Summit seems to show the low/reverse valve and servo. Am I correct? At $129, could I just get the kit and install just these two parts on the sick 700R4 and save the rest of the kit for a properly rebuilt unit (I'm trying to get a few more months out of the sick 700R4)?

I could put in a fresh TH350 for $550 (don't do much travel). But to keep the computer happy, the electric speedo I think needs to function (VSS sensor), and there are kits to make the TH350 spit out electric speedo signals. Though my 9" TH350 had a 7/8" speedo hole, I don't remember the 6" being that small.

I was told by several that the 700R4 tailhousing fits the 6" TH350? One person said it didn't. Anyone know for sure? Logic says if it did, B&M and Hurst wouldn't sell so many 3rd gen conversion kits, everyone would just grab the longer driveshafts.

Basically curious to know if the low/reverse boost valve and/or servo might help me out for a few months. I believe these firm the shifting, but installed alone do not "release" the clutch packs quickly enough, so some burning occurs. But I'm just after a bandaid.

What other work has been done to the vehicle? It sounds like you may have a TV cable out of adjustment... Look at that before you start to rip into the internals... The shift kit won't fix or help the problem so it's a moot point. In fact it may make it worse so That would be the last thing I would suggest.
Mark

No work has ever been done to this car in 5 years, it's bone stock, the wife's car, that's why I haven't suspected the highly important TV cable on the 700R4.

I too am a firm believer in no shift kit in old tranny's (from experience). But it's hard to resist a vette servo/larger pressure valve for the sick 700R4 since they can be installed easily and the unit seems to be dying anyway. I was hoping to buy some time with higher line pressure, but I do realize it could also kill it quicker. It's a gamble, just from driving the car, it just "seems" a bit more pressure on 1st gear would help the slipping. When I roll from a dead stop slowly, no loud bangs. But if I juice it, several loud bangs (like very loud shuttering of clutch plates) from the tranny (obvious minor slipping, but no RPM increase); car still goes forward at nice clip.

you didn't post what model of car your working on?
would it be a Camaro? if so check tranny mount if thats not it forward plates or forward sprag would be my guess, no help would come from shift kit it that case.....

It's an 89 Firebird, stock, 170HP V8. Tranny mount and torque arm rubber are in real good shape (as is the rest of the car/suspension).

Forward plates I'm guessing wear out, and Forward sprag could be cracked (still guessing)? Then I'd agree, higher line pressure would do nothing for a bad sprag. But extra holding pressure would not help worn forward plates (it's a snap to change to a vette servo on the 700R4)? Does "plates" refer to "clutch packs" or something else?

you know I just love you do it yourself guy's you ask a question, then someone that is a transmission re-builder will answer
and
you come back with well I guess it could be this or maybe that

I'll try what ever you think will help and put a side what the person has experience with that part of your car your asking for help with..... why ask if you don't listen

airworld,

very good points.

I've sent several emails to another DIY fellow with a gov gear problem on a 700.

they think I am confused since I am talking about worn out case bushings and ring gear area causing the plastic gear to eat-up in a few miles.

They keep asking for the answer for the gear trouble and are NOT listening to my explaination of the cause. Mayb they are doing something else wrong?

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At the Bonneville Salt Flats... 130mph is known as First gear ...............

To AIRWORLD2 and CROSLEY:

I value your experience as I have very little concerning auto trannys. EXACTLY (use the quote feature please) what did I say that made you guys think I WASN'T listening???

I totally agree (carefully read my last, unedited, post , I AGREE, line pressure probably won't do a thing, the tranny is toasted) with what you said about my tranny. I have no idea why you guys made the same comment. Enlighten me, please.

Your lack of knowledge/guessing is causing you trouble or you are listening to the wrong folks.

The corvete servo has nothing to do with the engagement of the tranny into gear as you sit stopped and shift the trany into "OD" or "D". The servo people talk about applies the band that functions for 2nd gear and 4th gear

many folks immediately talk about a shift kit to fix a worn out tranny.

Also the boost valve to replace is the primary/main unit, not the low/reverse boost valve.

As pointed out by airworld, most likely the forward frictions(clutch pack) are junk. Forward frictions are named for the fact that ALL power goes through them in forward gears.

Back to your OE question about a servo & boost valve to have the trany last longer...... it is a crap shoot. My advice would be to save your money and be easy on the car since it appears the tranny is near death.

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At the Bonneville Salt Flats... 130mph is known as First gear ...............

I've seen enough tranny failure to know my 700R4 is going bye bye. And if you read earlier, I clearly state a shift kit is a really bad idea for a dying unit, it usually makes it much worse. I am aware of the functions of the intermediate servo, the OD servo, the TV boost valve, and the low/reverse boost valve. But Thank You, sincerely, for answering my original question; I agree with you about adding those external parts now, it's likely too late and would be a waste/crap shoot.

I didn't think I'd be blasted for asking for "bandaid advice/diagnostic help" on a 700R4 that I already knew needs a rebuild; I won't make that mistake again. Yikes.

This "Do-It-Yourselfer" has been building motors and installing trannys and shift kits for 15 years, yet gets the "newbie" treatment because I'm not a "professional tranny rebuilder".

Anyway Crosley, even though you agreed with airworld earlier, thanks for your clear advice, it will save me time, trouble, & money, which is what I felt these message boards were all about.

Reading posts on any site or email is difficult to obtain the attitude behind the post.


I am guessing here..... but i believe airworld is somewhat new to the world of the internet and answering questions for people.

I've been at it for several years and hopefully avoid some of the mis-understandings.

My response on the DIY type person was not directly at you but at the general issue of folks not accepting advice when offered. On the flip side of that , how is a person to know if the advice is solid or garbage???


You may have not known that airworld knows what he speaks of with automatic trannys. I've had that happen many times...

I must admit to a bit of frustration at the time these posts were happening. I had emailed the same answer 3 times to some ppl that seriously felt I was off in left field about worn out bushings causing a plastic govenor gear to chew up in a few miles on a 700r4....


good luck

__________________
At the Bonneville Salt Flats... 130mph is known as First gear ...............

ok I'll be the first to admit I am full of attitude, but this aint my first rodeo either. The after market has drilled the idea of shift kits for years.
but if you would only read about them a bit first they clearly state that the only help transmissions that are working correctly and only intend the firm up the shift. they are not a cure for ailing transmission's.

I see the same questions over and over and the same answer about the cable setting and fluid change's will fix all your trouble,

I only try to help others but you cant fixem over the net and you cant rebuild a trans that slips without taking it out of the car. they still haven't put a mechanic in a can yet.
I make mistakes and spend many hours finding the trouble where I screwed up or simply missed something