Hey everybody, alright I have a 1991 RS with a lovely 700R4 auto tranny.

ok now to my problem... say your going down the road 60mph in OD and you go to slow down and maybe slowin down fast for something and what do you all do usually.... shift it down into D causing the engine to rise up in rpms due to the speed in that gear... thats all common sense i'm sure... but my car just stopped doing that... like I can be going 120 mph... and when i let off the gas or at any speed when i let off the gas the car goes back down to an idle.... and when i hit the gas the engines RPMs will rise and rise until it hits that gear its in so to say...

lets say i'm going 40 down the road... and i can put it down in first gear... and it will just drop down to an idle... i can sit there and rev the engine up and down up and down and say your going 20 mph in first gear thats 4500 rpm... (example) as i'm reving the motor up as soon as it hits that spot where the gear is it grabs it again and gos... sooo.... i know this is alotta here say this and that but its really hard to explain... if you need some more details let me know... i am really kinda lost on this one...


also original tranny 130,000 miles on it... tranny fluid and filter were changed at 120,000 miles and the tranny does really slip at all... maybe just a bit but nothing that noticeable... any more details needed let me know i think i got it all covered though i hope... thx again ...



vetter

 

Simple problem, not a simple fix.
It sounds as though the overrun clutches, or the overrun hub has failed.
Unfortunatly, there isn't a "simple" fix other than removing the transmission and dissasembling it to replace the failed componenets.

 

wow all that typing to explain it and one simple answer... i'm glad theres someone out there who knows this crap... is that the only possible problem then ?? or is that just a possibility ?? thx..


vetter

 

What you are experiencing is a loss of engine braking. The sole purpose of the Overrun clutches, is to prevent the transmission from overrunning, or provide engine braking. Only two things can cause the loss of overruning: Burnt or sheared Overrun Clutches, or a broken Overrun Hub. Both require removal of the tranny.

If its just the hub broken, consider it a parts failure and replace it. If the clutches are burnt, try and find out why. I had a Syclone that burnt up the Overrun clutches and I found the Foward Clutch Piston cracked allowing Foward Fluid to bleed off into the overrun circuit causing them to apply. Since they cannot be applied in 4th gear, it caused a binding condition and the overrun clutches were the weaker link and got smoked.

 

wow.. you would be the expert... thank you for solving the problem... i know i don't have a clue about trannys and i never woulda figured it out.... thx again...:hail: :hail:


Vetter

 

hey, could you give me an estimate at all on how much parts would cost and how much it would cost for labor if i took it in to get it fixed....

ya i know your all pry not mechanics who give out bids, but if you know or have a clue itd help, would anyone know what parts i'll need to order and what kinda price they'll run... I'm just wantin to get an idea on the amount of money i'll have to spend.

i know this is out in the blue question since there are so many variables but if anyone has had to have this done and could give me some figures itd be appreciated..... thx for the input..



Vetter

 

The overrun clutches (burnt), input sprag (broken), and overrun hub (broken), will cause this. Use new (inner race) or a perfect used one (not to common), along with a new 29 element sprag assembly. The hub (if used) must be in very good shape, or breakage can occur.

 

Well....a buddy of mine recently took his truck in to AAMCO. For them to diagnose the tranny internally, they charged him to pull it. That by the way cost him about $700. Incidently you can buy a rebuilt 700r4 for around that and put it in yourself. If you took it out yourself and brought it to them they would try to tell you they couldn't warranty it unless they pulled it out themselves . And then they would probably estimate the total at around $1200. Either way, tranny work is EXPENSIVE.

 

if i wanted to just replace the parts that are needing replaced... do you think i could be able to do it... or is this calling for an expert in the tranny department.... i know my stuff somewhat but should i leave this to the pros ?? since i'm going about and doing this... think it would be a good time to add a little to my tranny to step her up... like a shift kit.. or what else could I add to my tranny right now since its out to gain performance... i have a 91 305... was tbi now carbed with edelbrock 600cfm and stock tranny right now and stock rear end.... since i'm going to be droppin the tanny no matter what... what would be some good things i could add to it while its out... servo ? or shift kit ? specific things would be helpful... thank you .... also if i were to do this and not take it to the shop does anyone know of a good diagram of the 700r4 like a manual to it so i would have a better understanding when ripping into it...... and how long am i lookin at for getting this fixed... ??? I know i probably sound like i'm completely lost and you guys are thinking no way... but i have a friend that has added things to his tranny like corvette servo... and shift kit... and he knows alot and I am a fast learner... always looking for a new adventure... thx again..




Vetter

 

anyone else have some input for me ??