[Crazy-J]

Hi everyone,

I recently purchased a 72 Chevy pickup with a 700R4 transmission. On only my 2nd time out with it since the test drive 3rd gear started slipping. On my 3rd time out with it I lost 3rd completely and had to drive home in 2nd for a few miles

I am looking into getting it rebuilt now but the price estimates are $1500 min to $2500 max at all of the places I have talked to. I've looked online and I can buy a rebuilt 700R4 for $870 at the lowest from Bowtie Overdrives. They also said it incorporated some fixes for these transmissions while the local places say they are just rebuilding it. So I am thinking of ordering the transmission from Bowtie Overdrives and putting it in myself.

My question is, is there anything I should look for that may have caused this failure other than just a worn out trannsmission? As far as I can tell the swap was done well, with a locking torque converter, shortened driveshaft, & B&M trans cooler. There is also a B&M manual lockup switch that was in the off position when this happened. Is that right and what does manual locking it do?

I have no experience with this type of transmission so any help is very much appreciated. Thanks

[Crosley]

3rd gear has been a trouble spot for these trannys since they were introduced.

I would recommend a TransGo shift kit during the over haul. Depending on the year of the 700 , there are different TransGo kits that work well.

Updating to a higher count 3/4 clutch pack is a good idea too

[tnsmith10]

it sounds odd that 3rd would really give much of a problem in a 700r4, i know it happens, but in this case, to me, it sounds like 4th is the problem... reason i say is that lockup on those trannys is what feeds lube for 4th gear. without lockup, it could wipe out 4th within miles. (normally freeway driving or long trips without stopsigns or lights.)that manual switch i have seen used for the simple reason is that lockup really isnt needed for around town driving and it gives u the option of running without lockup. if it already has a kit for lockup thats supposed to engage lockup in a certain gear, (like 3rd or 4th) then having the extra switch gives u control whether lockup comes in or not.
those are not cheap trannys, i myself have 1 in my car and i think its an awsome trans... mind u, i went with a non-lockup setup so i wouldnt have to worry about higher gear issues... been in the car since 96 and still works like a dream still today.
depending on what u plan on doing with the vehicle, maybe going without lockup could possibly be a better solution rather than dealing with something else that can go wrong with the unit..
hope i was somewhat helpfull on this.

[Crazy-J]

To Crosley: Thanks! In factthe guy I bought it from gave me a TransGo **** kit that he never put in so I will have them put that in if I get it rebuilt or I will do it myself.

To tnsmith10: Thanks! You could definately be right since it basically only got freeway miles on it when I was driving it. I'll look into the non-lockup setup since it sounds less problematic. Do you know who makes the non locking setups?

[Crosley]

tnsmith10;

your statement about 4th gear lube confuses me. Lock-up is not what feeds the lube circuit on the 700/4l60 tranny.

lock up in the 700 reduces the lube flow through the converter , then into the cooler , then into the tranny lube system. There is less oil flow needed in lock up since the primary heat generator ( slippage in the converter) is removed from the equation.

You can easily increase lube flow during lock up by drilling the restrictor plug at the lock up valve out to .110

the only thing that changes with the shift to 4th gear is the apply of the band for over-drive. the 3-4 clutch pack remains applied. That is why over drive is lost with a 3rd gear failure.

[ronb]

do you have a tv cable hooked up? if so to what? quad or holley carb? your post stated it was a 1972 I assume it is carbed?

[Crazy-J]

Originally posted by ronb
do you have a tv cable hooked up? if so to what? quad or holley carb? your post stated it was a 1972 I assume it is carbed?

I'm not sure about the TV cable. Where would I look for it? The truck has an Edelbrock 600 CFM 4B carb.