73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 79BONANZA on August 09, 2002, 05:05:00 PM

Post by: 79BONANZA on August 09, 2002, 05:05:00 PM
Hey guys,  lot's of really great information here and I'm eventually going to make the switch from whatever I have in my truck to a 700r4, but how do I tell them apart from looking at them.  My truck is a 1979 Chevy Bonanza 4wd Automatic.  Just dropped a rebuilt, 30 over, 350 4-bolt main in it with headers, a edelbrock performer intake, and a edelbrock 600 carb, 2.5inch pipe with flowmasters.  Want to shop around for a 700r4 to rebuild and put in my truck mainly for the overdrive.  What are the visual differences in these chevy transmissions???  Any help would be greatly appreciated.



Title: tranny ident.
Post by: oscarone on August 09, 2002, 07:39:00 PM
Crawl under your truck and take a look at the pan.  The TH350 looks like a square with one corner cut off and the modulator is on the back of the case.  The TH700R4 is basically square with 16 bolts, it has no modulator as I believe it is electronically controlled (keep that in mind if you plan a swap).  The TH400 has two straight sides, the modulator is on the side of the case.  Also, when you swap trannys remember t-cases were mounted differently...output shafts may be different...drive shaft lengths may change...

Title: Re: tranny ident.
Post by: 79BONANZA on August 11, 2002, 04:15:00 PM
Thanks for the info, as soon as I get my truck back I'll take a look at it.  Its getting new rocker panels.:rollin

Title: Re: tranny ident.
Post by: RSBAD454 on September 19, 2002, 04:40:00 PM
why are you going with a 700R4? my friend has one in his 72 2WD and it had no impact on gas mileage. he said it got the same in D or Over Drive. watchout what year 700 you get cause the earlier ones were very weak compared to newer versions. id go for the 4L60E if you can find one.

Title: Re: swapping trannies
Post by: Snuke87chevy on September 19, 2002, 06:08:00 PM
I have a 700r4 in my 87 and I think that it has lots of power in it.  It's first gear is lower than the TH350 or TH400.  However, if I could pick, I'd put the SM465 4-speed manual in mine.  I have one, it's just a matter of finding enough time to swap them out.  Putting in a manual takes a little more work.

Title: Re: swapping trannies
Post by: RSBAD454 on September 20, 2002, 10:51:00 AM
how does your tanny have lots of power in it? if its a stock motor then the tranny may hold up, but 700R4's need to be built to withstand the vigors or HP and especially the weight of 4 Wheel drives with big tires.

Title: Re: Swapping Trannies
Post by: Snuke87chevy on September 21, 2002, 12:35:00 PM
I do have the stock 350 in my truck.  I do agree that there is no difference in fuel mileage between a 700r4 and a TH350 or TH400.  The 700r4 was originally only offered in trucks with diesels.  They later offered them in gas trucks.  Mine has power b/c I don't go mudding or off-roading.  The only work my truck sees is farm work, and the low first gear comes in handy when I'm pulling wagons.  On top of that, I can beat people out of stop lights with it.

Title: Re: Swapping Trannies
Post by: RSBAD454 on September 23, 2002, 10:20:00 AM
so why not put lower gears in your rear end? way cheaper for you to do. if its 4 wheel drive, you can put it in wheel low and blow doors off stop light to stop light..............id go the gear route.

Title: Re: Swapping Trannies
Post by: Snuke87chevy on September 23, 2002, 07:28:00 PM
I'm not sure exactly what gears i have in my truck, as the sticker in the glove box is gone and I'm not about to take the rear end apart just to do some counting.  I'm guessing I have 3.73 or 3.42.  I dont want any lower gears b/c i'd like to keep my fuel mileage in double digits.  I am not fixing to change anything until it breaks.  That way when it's repaired it has all the mods that I want i.e. if my rear-end goes out, i'll re-gear a 12-bolt posi rear (i have a truck with all these cool parts in it: 4-speed, rear axle, a/c) and stick it in place of my 10-bolt.  On top of that, most of my money goes into college expenses.

Title: Re: Swapping Trannies
Post by: RSBAD454 on September 24, 2002, 09:35:00 AM
first off counting teeth in a rear end doesnt require tearing the rear end apart. if you have a ten bolt bolt just take all the bolts off that hold the cover on. pull the cover off, sometimes there is a tag that says what the gear ratio is. if there isnt a tag just count the teeth on the ring and the pinion. i think you divide the number of teeth on the ring by the pinion. not that hard. your worried about gas mileage now when you got done talking about blowing people away with a lower first gear? lol  its all good.

Title: Re: Swapping Trannies
Post by: Snuke87chevy on September 24, 2002, 06:18:00 PM
yeah, i guess if i was really worried about gas i wouldn't be driving a 4x4 truck.