700r4 behind a 472 caddy? Can it be done?

Was wondering if a 472 would hold up behind a 472 caddy. Any one have any idea? Thought it would help with the gas mileage. Thanks.

 

it can be done.
expensive though.
you need an adapter and special starter.
do a search theres a few different companies out there.

 

The Caddy guys tend to say "why?" for this swap - just use a 2.91 rear end, the low-end torque from the Caddy motor can handle it. But like Ryno says, ask on the Caddy sites. It can be done.

 

I have been looking on those sites, but they always use these in the 4x4 trucks and such. This will be a cruiser. I already have a 700 set up in the car is the reason. I have the adapter already as well. I used it in a buick to chevy app before. The main thing is will the trans hold up to 500 foot pounds of torque. I am not sure. The 700 I have is out of a police car. An 89 model. Any info would be appreciated.

 

It could hold the power if built to do so I'd imagine. If tring to use a stock used one ,well who knows the condition

 

Yes, good point. I have the 400 for the caddy, but thought this would be better and better on economy. I am building this to be my daily driving car. It's not an economical engine choice i know, but I thought it might do the trick.

 

Right now Gearstar Transmissions has some terrific deals on GM trannies. They are offering complete 700R4 units, capable of I think, 400 hp, with converter, fluid and free shipping. I think they are $1495. Being "built", it probaly would hold up fine in normal driving.

On the other hand, I agree that a super low numeric rear axle (2.41 for example) and a TH400 would do the job very well too. You pays your money and you takes your choice.

Ray

 

Indeed. I know the rear axle will have to change. It's a 3:42 pos. The 400 was in working condition. The engine had a bad cam and bearings, so it's down for a rebuild. I will probably do the 400. Any ideas on what kind of mileage one could expect? I hear rumors or 8 to 10 and promises of 15.

 

Geez, I hope those mileage figures are wrong! It will depend on several factors, I think. What kind of car is this going in and what it weighs, just to name two. Also, of course, how it is driven. You mention it being a daily driver. Is that all in town, out of town or a combo of both?

I have a 500 Caddy and a TH400 that I acquired recently.......with thoughts of putting in my '40 Buick Super.......which the 'book' says weighs about 3700 lbs, though I suspect it is a little heavier than that. But my intention is to do exactly what I suggested to you.......a TALL rear axle and let the torque do the work and I don't expect to be pushing it hard. Justa cruiser and travel to car events.

Ray

 

It's going in a 55 buick century, my avatar. I intend to change the gears out to higher ones soon. I just found a cam from mts that says it gets in the upper teens and low 20's for gas mileage. All my driving is intown and to and from work, 40 miles round trip. It will be a cruiser indeed. Not looking for power, although it is there, just cl***. Any ideas?

 

I have a 47 Chevy sedan with a 472, turbo 400, 9" with 2:78 gears, 28.5" tall rear tires. I get 20 to 22 miles per gallon at a constant 70 mph on the interstates. I get around 14 in city driving. Go with the 400 the stock 700R4 won't handle the torque, maybe if you never get on it it might.

 

How could you not get on it though? I mean it's got it. I thought the same thing. I could maybe baby it, but who am I kidding?
20 to 22, impressive.

 

Is your 472 stock or did you change some stuff on it to get that?

 

You can build up a 700R4 to handle the power level, but, by the time you do that, you are in the range of the price of a Gear Vendors Overdrive, or past it, if you can find a good used one. Stick that on the back of the TH400 and get six nearly indestructible gears.

 

Ditto! I picked up a THM400 w/converter and the GV OD for $600 for behind
my 500 Caddy.

 

Basically stock rebuild, after market cam same specs as stock, good valve job, new bearings, stock intake with a 650 Holley spread bore carb, hei dist, big block Chevy headers, nothing special. A lot of tuning with the adjustable vacuum advance and the carb to get it right. I could probably get better mileage, but I can't keep my foot off the gas pedal. I've had this engine in the car since 1994 probably at least 100,000 miles still going strong. Cadillac 472-500 are great engines they will find the weak link in your drive train. Good luck with the Buick, looks like a really nice car. JJibs

 

i put a 500 in a one ton gmc crew cab 4x4 back in the 80s. the best it got empty was 12 mpg, about 8 loaded heavy. it was a towing animal! i always wondered what that 500 would be like in a lighter car.

 

how well does a gear vendors overdrive work for mileage like that? Does it make that big of a difference?

 

The big Caddy will kill a 700 in no time flat! Go with the 400 and some highway gears.
Headers are a must!
Dont waste your $$$ on the Edelbrock aluminum intake, unless you want it to look cool or loose a few pounds.
There's an AMAZING amount of power to be gained by cleaning up the heads.
It's impossible to put too much carburetor on top of one of these beasts. If you still got the stock Q-jet, and it's original to the engine, it's one of the good ones, just tuned down for the luxo-barge crowd... Have a knowledgable carb builder give it a performance re-bop and you'll be happy.
If you need new pistons, dont worry about hunting down a set of 10:1's. They make great power with the replacement 8:1's, plus you can dial in a lot more timing with the lower compression.
Speaking of timing, go talk to the buick guys on v8buick.com. There's a dude over there who re-bops distributors for the 455 crowd, and he's done a few caddy's as well with spectacular results.
Stick with the HEI, but add an MSD box with a limiter... Over-revving a caddy will kill it instantly!!! Keep it under 4500-5000 R's, and it just might live forever!

Something else, the caddy seems to LOVE nitrous. Some guy on the MTS forum has made over 800HP on a bone stock 500 with naaaz... No, not traditional, but worth pointing out.

And as already pointed out, that beast will find the weak link in your drivetrain.

 

Dont do it... Go check out the MTS forum. There's a post on MPG..

The big caddy has a sweet spot in it's RPM range where it runs most efficently, and will return the best MPG. Surprisingly, overdriving it may give worse MPG.

 

I run a 406 c.i. chevy t400 with 2:72 rear gears and 225/75r15 tires on 6 in. rims. That said it goes 80mph at 2500 rpm on tach. If I hold it down to 2200rpm I get 18 mph. I know this isn't caddy but, numbers should workout just the same.

 

Untouched '89s have been good to me for some reason. I got one behind my 500.


Truth is, the mileage is only a hair different than with the turbo 400. Not really worth it in my opinion.

If I had it to do over again, I'd go with a solid turbo 400.

 

A solid 400 will get you home, the 700 is expensive, the clutch pack is small, and if you burn up a couple, you will find yourself obsessed with the smell of burning clutches --like dogs imagine a squirrell is closeby(even if he isn't there!).

You will , really notice the smell of hot brakes from semi trucks too, thinking it COULD BE the 700 going out again.

That is of course, if you burn up a couple of 700r4's.


mine is in a '60 Caddy 2 dr.

 

While high rear gears (low numerically) are one way to keep RPMs down at cruise, overdrive autos allow you to do that and more, with their extra gear and lock up converter. T400 equipped cars were never noted for their fuel efficiency anyway, even when coupled with lazy rear end gears.

That 3.42 rear end gear sounds just about perfect to run with an overdrive even behind the 368-425-472-500 Cad V8s that top out around 5 grand in RPMs, so if your adaptor is for later Buick V8s with the corporate pattern, instead of being in a big hurry to change out the 3.42 ratio rear for something else, try running the 700 at least until you find a Gear Vendors unit like mentioned above to go behind the T400. Otherwise I would recommend the T200R4 because most all have the corporate B O P C bellhousing pattern (actually most all are dual pattern) making them a direct bolt up to the Cad block. They are reputed to be a stronger transmission than the T700R4 when built up with aftermarket parts, too.

With street tires being the probable weakest link, provided you don't beat on it too heavily, that T700 might last a while (maybe even a LONG while), even behind a 500 inch Cad.

 

Call www.bowtieoverdrives.com
They build the 2004r way stronger than the 700r4 and it wont need an adapter.

 

You can't always just simply slap an overdrive unit, or an overdrive transmission into a car and expect better mileage.

Your rear end gear ratio must be, or be selected to be "correct" for keeping the engine in its most efficient operating range, at the desired cruising speed, with your desired tire size.

Toss one into a car that already has tall gears, and you will be lugging the engine in top gear, and wasting fuel.

Take my A, for instance. It has a 0.50:1 6th, 31" tires, and a seemingly impossible rear ratio of 6.50:1. Humming along at 2300 gives me 65 mph, 28 mpg, and smokey burnouts from tread to tubes.

 

If you're driving around town then the time spent in the overdrive gear isn't going to be that much anyway. The advantage would be that you could leave the lower ratio in the diff for better acceleration and lower consumption on acceleration(acceleration to speed will be faster and you won't have to use as much pedal) while not sacrificing highway economy.

 

Man, I really appreciate the help on this. I had found a 200 r 4 but had hear that they wouldn't hold up either. I think that if I get it built a little beefed up, it might work. I am going to try the 3:42's for a while and the 200. See what happens. Any ideas what needs to be done to the 200? I am not going to drag race, just cruise and daily commute.

 

I agree with 'nofin' on this. The 3.42 and th400 will provide spirited around town driving and you won't have to lean into the throttle as much every time you take off. However, if you are using a short tire then the 3.42 may be a bit deep and something in the 2.7-3.1 may work better.
Back when the factory engineers were laying out the drivetrain they had to consider what combo would provide the best mileage for the given curb weight and at what rpm it should happen. Your car is likely lighter that a D'ville so even with similar **** gears you will gain some acceleration and since the engine will not be working as hard you should see decent mileage. As stated, they are torque monsters that do their best work under 4500 rpm in relatively stock trim.
Check the factory info and see at what rpm they listed max torque and use that as a guideline for tire dia and gear ratio at whatever cruise speed you need/want.

.

 

Call Bowtie Overdrives! They build 200s to withstand 700 hp daily. A guy in Holland has bought 6 and has over 600ft lbs torque and beats the hell out of it. He resells them over there. Talk to Chris Chandler.