Thread: 700R4 Noise and Fluid Temp Issue

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I have a 1983 Chevy Van Motorhome, which I guess hardly qualifies as a hot rod. Still hoping to find some knowledgeable people here to give some advice.
The vehicle has a 6.2 non-turbo diesel engine. The original transmission was a TH400, which I replaced with a rebuilt, beefed-up (700hp) 700R4 from what I thought was a reputable transmission shop. It has a lock up torque converter.
I talked to the shop about my problems but didn't like very much what they told me. So I'm trying to get a few more opinions here.

Here are the issues I have.

1. The transmission shifts fine and performs nicely and quiet up to 3rd gear. In overdrive it emits a slight howling noise, most pronounced around 60 - 65 mph. If I engage the lock up the howling gets much worse to the point where you want to disengage it right away. If I keep it locked and go faster it quiets down somewhat but the noise is still there and it simply shouldn't be with a new tranny.
There is absolutely no noise in 3rd gear, with and without lockup.
The front part of the drive shaft had to be shortened. I had this work done by a professional drive shaft shop. My first suspicion was that the drive shaft was out of balance but the people who shortened it assured me they balanced it.
The drive shaft has all new u-joints and a new center bearing.
Has anyone any ideas on where the noise comes from?

Note: here is what the transmission shop told me. My lockup solenoid gets 12V from a separate brake pedal switch to allow disengaging of the lockup when braking. The ground wire runs to a dash board switch and then to ground. They think there is a bad or insufficient ground for the lockup solenoid. They think I should ground it right on the tranny and put my dash switch in the hot line.
I'm having a hard time believing that's the problem but I might be wrong.

2. I also have a temperature problem. When cruising on the highway at around 55 mph the fluid goes to about 230F, around 70 mph it is up to about 250F. This is without the converter locked due to the howling problem mentioned above.
The transmission shop people said it was not a problem to drive the 700R4 without lockup, but I have read other statements just to the contrary. I'm not using the radiator integrated oil cooler but a 20,000 lbs GVW rated stacked plate cooler in front of the radiator.
Now my temperature problem is probably related to not using the lockup. I'm still surprised that the transmission generates that much heat.

I'm not sure if I mentioned everything that is important. If something's missing let me know. I would really appreciate your input.

Those temps are gonna cook the trans to an early retirement. I had a lengthy chat with the owner of Bowtie Overdrives many years ago. He stated that for every 10 degrees over 220, the trans life is shortened by half. Under normal driving conditions/temps, the trans should live around 250K miles. You really need to use the radiator trans cooler first then run it through the stacked plate cooler second. I dont believe the stacked plate cooler is sufficient as the primary cooler. This will drop your temps a ton. As far as the growling in 4th gear, the only difference between 3rd and 4th, is the 2/4 band is applied. I wonder if it's slipping? Have you put a pressure gauge on the trans to see what your pressures are? As you may or may not know, the 700R4 has the tricky TV cable, that controls line pressure. Not enough and she goes up in smoke. Something this trans has a very good reputation for.

Keith

Thanks Keith for the reply.
I initially ran it with the radiator trans cooler only, and the temperatures were similar. I figured that a large external cooler has better cooling capacity than the radiator cooler. Apparently it doesn't. My next step as far as trying to control temperature is using both coolers, as you suggested.
I am aware of the TV cable. I had to fabricate a bracket for the TV cable as they aren't available anymore, at least not for the diesel engine. The injection pump does have a hookup for the cable. There are diagrams available that show the correct geometry of the TV cable hookup, and I followed that closely. I used the wide open throttle method to adjust the cable, which basically means max throttle equals max travel on the TV cable. I have not checked the line pressure, which I should probably do. Where exactly is that pressure reading being taken? Also, can you give me the procedure on how to do it?
You say the only difference between 3rd and 4th gear is the 2/4 band being applied. Isn't there another major difference? In 3rd gear the ratio is 1:1, meaning none of the planetary gears are actually being used, while in 4th gear, with a ratio of roughly 0.7:1 the drive shaft runs faster then the engine. Could the howling be coming from the planetary gear set? Then why would it be so much worse once the TC lockup is engaged?
Steve

I'm not a tranny guy, but you mentioned that the tranny shop questioned your ground bring good for your lockup. Do you have your engine, frame and body bonded together with good, clean ground straps on bare metal connections? You can very easily check your ground circuit by running a temporary jumper wire from the isolated side of your lockuup switch direct to the battery, then try your lockup switch. If the noise goes away the shop was right and you have an easy fix.

Try to go with the TCI constant pressure valve body the eliminates the need for the critical adjustment of the TV cable.The TV cable is then used for a kickdown only.There are two reasons I am suggesting this-one being it is a custom set-up and the second one being these trans do rely on that TV cable adjustment to be correct and I think the heat up issues are directly related to the trans slipping.I think it is your interest to contact TCI tech to talk about the issues your are having.

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The pressure tap is on the left side of the trans above the shifter. You want to make sure you see an immediate rise in pressure when the throttle is slightly advanced. That diesel has mongo torque, you don't want to fry the clutches due to low line pressure. It's cheap insurance to check your pressures. Per my ATSG reference books I have, it says for D4-3rd gear: fwd sprag holding, fwd clutch applied and 3/4 clutch applied. For D4: fwd sprag clutch NOT holding, fwd clutch applied, 3/4 clutch applied and the 2/4 band applied.
If the problem happens only when the converter is locked I would manually lock it in D3 via a manual switch you can wire in. Good old fashion troubleshooting! Running both coolers will get the temps down to reasonable levels. Run it into the radiator 1st then the aux. cooler second.

Keith

How much does the whole rig weigh??? Possibly more weight then you have transmission????

Wow Ive never heard of a 700r4 behind a diesel with the torque and all, I was sweating it out just wondering if it would hold up behind my sbc 383, may be common don't know. I did put the TCI constant pressure valve body in mine just for the reason that with 2x4s I was afraid I wouldn,t get the TV cable set correct. Bowtie overdrives helped me out with the correct carb. linkage adjustment for the cable. I also put a Gear vendors overdrive but have yet to really test the combo except around the block, long blocks.Hope I didn't get to far off track here, but trans temps were stable,pressure scared me! also just going thru radiator for cooling, but not trying to move 4000 plus lbs

Originally Posted by blwn31

Those temps are gonna cook the trans to an early retirement. I had a lengthy chat with the owner of Bowtie Overdrives many years ago. He stated that for every 10 degrees over 220, the trans life is shortened by half. Under normal driving conditions/temps, the trans should live around 250K miles. You really need to use the radiator trans cooler first then run it through the stacked plate cooler second. I dont believe the stacked plate cooler is sufficient as the primary cooler. This will drop your temps a ton. As far as the growling in 4th gear, the only difference between 3rd and 4th, is the 2/4 band is applied. I wonder if it's slipping? Have you put a pressure gauge on the trans to see what your pressures are? As you may or may not know, the 700R4 has the tricky TV cable, that controls line pressure. Not enough and she goes up in smoke. Something this trans has a very good reputation for.

Keith

I'm getting a pressure test kit to take line pressure readings.
I'll post the readings once I have them - it'll be a few days.
Thanks for all the replies!
Steve

Originally Posted by Dq383500

Wow Ive never heard of a 700r4 behind a diesel with the torque and all, I was sweating it out just wondering if it would hold up behind my sbc 383, may be common don't know. I did put the TCI constant pressure valve body in mine just for the reason that with 2x4s I was afraid I wouldn,t get the TV cable set correct. Bowtie overdrives helped me out with the correct carb. linkage adjustment for the cable. I also put a Gear vendors overdrive but have yet to really test the combo except around the block, long blocks.Hope I didn't get to far off track here, but trans temps were stable,pressure scared me! also just going thru radiator for cooling, but not trying to move 4000 plus lbs

The transmission place knew the vehicle specs.
I have seen statements on other forums that said something like "a stock 700R4 isn't gonna make it a week in a 1-ton chevy van or truck."
Pretty much all the well known transmission places build several levels of beefed-up transmissions, calling them different names.
Mine is level-2 of three available levels. They say it's made for 700 hp and the corresponding torque. The 6.2 diesel only has around 120 hp.
So I'm fairly confident that my unit is built strong enough to handle the weight of the motorhome.

Originally Posted by Dave Severson

How much does the whole rig weigh??? Possibly more weight then you have transmission????

Good question. I think the maximum GVW is 10,500 lbs. I'll have to drive it over a scale to find out the actual weight.
As I said it's not just a stock 700R4 but a beefed-up version.

Honestly, the transmission shop that built it should stand behind it. I hate when you pay good money, and now it's your problem. It's sad what has become of many businesses.

The 700R4 was installed behind diesels. So, they can handle it. I believe they have a different convertor, has to do with the over-run circuit of the trans. I briefly remember reading about in one of my ref. manuals.

Keith

I would think a diesel 700R4 would have a much lower stall speed to hold down the "R"'s and take advantage of the torque.Toni my trans guy told me awhile ago is the biggest problem a 700R4 has is it doesn't circulate tranny fluid very well while locked up.That is one of the main reasons while towing in other than flat land even with a cooler you tow in 3th.I got to wonder how the wt of the RV effects that.Now I want to say that in my build plans I am going to use a TCI parts rebuilt 700R4 with a high torque 383 going in about a 4,000 lb Astro van towing a 3500 lb trailer.But in all fairness,we use to have a Suburban with Art Carr parts in it towing anything from a 6 x 8 trailer to a 22 ft trailer.We would check the fluid in Buffalo and go to Cleveland,Ohio.When we got back,you could see partials in the fluid and we didn't beat on the truck at all towing mostly in 3th.After awhile of owning Suburbans with 700R4's we actually on purpose bought a earlier model so we had the use of a 400 trans.As I think about this more,I think a 400 with the Gear Vendors trans is a better set up than the 700R4 with one.You could also get more feedback on this RV site.Look under the Vintage section for RV's.

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I just figured my fuel economy for a recent weekend trip! Actually first trip with the 700R4.
I only got 11 mpg with the 700R4. With the old TH400 3-speed I was getting 18 mpg, and the overdrive transmission was supposed to improve it.
There is definitely something wrong. What are you guys getting with the 6.2 and 700R4 tranni?

I don't have enough miles on my setup to give mpg, although I don't expect it to be good. In just the little driving I have done I can tell with the 700r4 there's no way with the gear vendors I can pull double overdrive as the engine is just out of the sweet spot,
What I'm getting at is I wonder if when your in overdrive could you be off the sweet spot? I know it's a diesel but isn't their a cruising rpm that is preferable.