View Full Version : 700r4 Conversion Complete
The swap done; out with the 400, in with the 700r4.
Here's the stats so far:
18.5mpg with the 700.....15ish with the 400. And I was driving 65 instead of 55. I actually passed two cars the freeway.
The initial test run with the 700 was with the cooler lines plumbed to the radiator only. This maintained a tranny temp of about 190*--same as the engine temp. What was alarming to me was that when I left the freeway and got into town, the temps were flirting with 200*.
Immeadiately after that first run I found a good auxillary cooler and just finished installing that last night. The plumbing is now tranny to radiator to aux cooler, and back to the tranny.
Took a good long test run during my lunch hour today and the tranny temp never got above 125*. Driving just the Surburban, 65mph on the freeway, about 50* and rainy outside. Can a transmission run too cool? The transmission output line felt good and warm though
A few things about the 700r4:
The tranny shop built me a beefed up non-locking torque converter. They made provisions to the pump to accomodate the converter. Installed a heavy duty shell, and a shift kit. New 3/4 clutch pack and few other things from the rebuild 11,000 miles ago by the previous owner (a good friend). According to the shop, there is not much more that can be done to this little box. Shifts are firm and smooth, much less of jolt than the TH400 had.
Will probably do some towing this weekend and see how it performs.
Why the non-locking converter?
No electrics to mess with during the conversion, and one less component to potentially fail.
It was the tranny shop's idea--I didn't know it was an option. You should hear him go on about locking converters.
With the non-locking converter, the transmission will generate a lot of heat while in OD. Sounds as if you are prepared for that, but that might explain the high temps on your initial test run.
convert2diesel
04-30-2010, 10:35
No electrics to mess with during the conversion, and one less component to potentially fail.
It was the tranny shop's idea--I didn't know it was an option. You should hear him go on about locking converters.
You hang anything onto the back of your rig and you had better keep your eyes glued to that tranny temp gauge. Even with the cooler, the torques in the 700s were designed to lock up. The real source of heat comes from the torgue. If the input speed is higher then the output speed then its cooking the fluid, ergo your experience with rising temps in the city. You need it unlocked in high power settings, but once on the road at constant speed, there is no need for the torgue to be anything other then along for the ride.
I have towed with these trannys for going on 30 years, always in 3rd gear and always locked up when possible. With the exception of the current vehicle, (4l60E) I have never lost a torgue convertor and have never cooked a tranny.
Unless this guy has somehow managed to adapt a torgue from a 400 to work in your transmission, then I can only conclude that he is looking for additional work from you in the near future. You would have to take the internals apart and completely re-design the turbine and stators to achieve any form of reliability. I suspect your guy is really into drag racing.
A good replacement lock-up torgue is available for 2 to 3 hundred bucks with the carbon fibre clutches and it will pay for itself in fuel mileage and maintenance. As far as the electrical hook-up, it can be accomplished as simply as hooking up a switch on the dash.
Bill
Well, so far I am hoping for the best and trusting this guy at the shop. Really I don't know enough about transmissions not to. According to him, the way he rebuilt the converter and modified the pump, the transmission will run cooler than it would with the lock up. I plan on keeping close tabs on the gauge as I tow my trailers-the heaviest of which is 2,500lbs loaded. I'll let you all know the results after I make some trips. The first trip (weather permiting) will be this Sunday; and I will pull the smaller of the trailers which is about 700lbs loaded.
Because of the swap to the 700r4, I realize I have pretty much resigned myself to pulling my two little trailers. I think I'll take the heavier one for a test run before I load the family up, I don't want to find out that this set up will not work with everyone in the truck. That would really be a bummer, in more ways than one.
So I am keeping my fingers crossed.
Took my pop-up trailer (2500lbs) for a 35 mile test drive this week. About 32 miles on the freeway and then back into town and up long, steep grade. Transmission never got above 140*. 58* outside temp
Everything seems to be working right, and and I am very happy with the swap. Driveablity has increased dramitically.
Glad to hear all is well.
The Non lockup is an OK idea. The converters for the 700R are small anyway and the lockup components take up a lot of room in the converter housing.
By eliminating the lockup clutch and all its parts the converter shell can hold larger internal parts.
If you are going to use the thing hard, this is not a bad way to go.
To build a 700R to the "nuts" its about $2K
I have built a few and the list of needed aftermarket parts is long and $$$$$$$$$$$$$$$$$$$$$$$$$$$:eek:
Sounds like you got a great thing there.
Missy
Seems like it is a great thing. Hopefully it will stay that way. I've got about a 4,000 mile road trip in July, with the camper in tow. This trip is main reason I went foward with the swap. Well, that and the fact that I got the transmission and the Jimmy it came out of in trade for a canoe, two paddles, and a bottle of bourbon.
All together with the upgrades and install, I'm into the swap for about $1,400 and there a still a few pieces of the Jimmy to sell off to help offset the costs.
Made a 190 mile road trip this weekend, pulling the camper trailer and a canoe on top of the suburban. The transmission held steady at 160*, 82* outside air temp. My engine temps are too high for comfort, though. Held steady at 210*, got over 220* up a long, steep grade. Going to see if I can improve that some, starting with a good cooling system flush.
MPG's were poor (13.5), that is if I did my math right. Since the swap my speedometer has been way off. When the speedo reads 70 mph, actual speed is 60 mph. So I did this: 60/70 = .857. I used that as a multiplier for the odometer as well. So if the speedo and odometer are off by the same, then I suppose the math is right. I would not be suprised if that is the actual mpg's. The trip there was quartering into a stiff wind and the trip back was against a stiff wind.
Regarding the cooling, take a look at this recent thread:
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=36958
Your MPG calculation seems right on. Considering that you have a non lock up torque converter, you are going to loose some fuel economy. Your transmission rebuilder claims a non lock up torque converter will improve reliability so reduced fuel economy may be the price to pay for improved reliability. When you are towing, there is even more slippage in the torque converter. The slippage wastes fuel in the form of heat that has to be expelled. Basically, the more heat generated, the less power is being put to the ground where it matters to rotate the wheels.
Also, make sure that you’re towing in 3rd (direct drive). The torque converter will generate less heat and the transmission will last longer. The 700r4 was never intended to handle much power for extended periods of time in overdrive.
Thanks for the link. I'll check it out.
I have been towing in OD, mostly just to see how it does. On the flats the truck pulls well, but it doesn't take much of grade to slow it down. At that point I let it slow down or shift down into 3rd.
I'm not pushing it much and don't intend to. For the long trips I'd like to be able to take advantage of the overdrive so long as the engine and transmission are happy. My trailer weighs in at around 2500lbs...3/4 clutch pack has been upgraded....the manual says that towing in OD up to 4000lbs is OK. The transmission shop says that OD towing would be fine. But I am careful about it because your thoughts and most of the other thoughts out there are not to tow in OD.
Still in the 'testing it out' stages, so all opinions are appreciated. How would I know if the transmission should not be in OD while towing my trailer? So far temps have been good, and this last trip would be pretty typical of most throughout the summer. Would high temps be the sole indicator? Or am I faced with goods temps, thinking all is well, and then catastrophic failure?
I hear of people getting by with it but the 700R4 is particularly weak in over drive. Over drive on this transmission was meant for cruising down the highway while under light throttles. It was never meant to take full power especially from a diesel engine. You might get by with it for a while but if long term reliability is your goal, keep it in 3rd. You also have to remember that you also loose some efficiency from the gear reduction. So it’s possible, you may even see your fuel economy go up slightly towing in direct drive.
So it’s possible, you may even see your fuel economy go up slightly towing in direct drive.
As I was driving last weekend, I was wondering if that may be the case. There were times when I could feel in the pedal tell that towing in OD was not the way to go. As I would press on the pedal, there was really no response..that is no increase in speed or the truck would keep on slowing down. I was thinking at that point I am probably just wasting fuel by pressing the pedal. Then I would downshift to third or just let it coast up over the incline.
This only occured a few times throughout the trip. The terrain was rolling hills. Most not very steep, but some a little longer and a little steeper than the rest.
As I would press on the pedal, there was really no response..that is no increase in speed or the truck would keep on slowing down. I was thinking at that point I am probably just wasting fuel by pressing the pedal.
When I am towing with my 82 6.2 diesel Suburban, I always keep an eye out of the side mirrors and monitor the exhaust. When I am pulling a hill, if I see any black smoke, I back off the throttle until it clears. As the rig slows down and rpm’s decrease, I continually have to back off the throttle to prevent black smoke. Creating black smoke is just wasting fuel and not producing any more power. When pulling my 5000 lb travel trailer, I was getting about 15 mpg at a conservative 60 mph. So far, I have about 80k miles on the transmission and haven’t had an issue. It does have a lock up torque converter.
Back from the road trip and then some. Opted to not pull the trailer to tent instead; saved a bunch of money on fuel that way. HOT and HUMID back in the upper midwest. Transmission temps 130*-150*. 20.5 mpg was the best I saw, with ideal conditions. Once the A/C is on, I saw a 10% drop in economy. Add in a 30-40mph crosswind and MPG's dropped to 15.7.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.