Very happy with 700R4 in M1009

Last weekend I put a 700R4 with NP241C in my M1009 with 4.10 gears in a 14 bolt FF axle and 315/75R16 BFGoodrich T/A KO2 (34.5" diameter) tires. This is the truck in my avatar.

I built this tranny about 2 years ago during a long, cold Montana winter but did not have the time or energy to make the switch sooner. Now I wish I had bolted this drivetrain in the truck the day after finishing it. The M1009 drives so much nicer with the 700R4.

After a couple short test runs in the last few days, I went on a 150 mile roundtrip today with about 40% interstate, 40% rolling hill highways, and 20% steep and tight mountain roads.

The M1009 with the bigger tires and 4.10 axle ratio did always well in the mountains with the TH400 but everything faster was painful. Now it actually feels like a truck on the highway/interstate and not like a chainsaw with wheels. The combination of transmission gearing, axle ratio, and tire size is perfect.

The truck is both lively while accelerating from a stop or out of a hairpin turn and much, much quieter at the top end. I did not go much faster than 70 mph today due to traffic. Cruising on a highway feels now very similar to burbling down a forest service road. The engine is slightly below max torque and moves the truck effortlessly. Reminds me of a downeast lobster boat at economy cruise.

I wired the TCC up for engagement via a push-button and disengagement via the brake light. This setup makes the 700R4 feel like a 5 speed transmission. With the TCC locked the automatic downshift into 3 (still locked) takes care of regular grades. If it gets steeper a quick tap on the brake will get the torque converter going, which will take care of even the steepest grades here in Western North Carolina. In really tight turns it downshifts into 2 and accelerates out of the turn smoothly and swiftly (for its power to weight ratio). Downshift into 2 with the TCC locked needs to be avoided as it is very harsh without the converter fluid acting as a cushion. The double downshift acceleration from 4 is impressive in the unlocked mode though.

I am certain that a similar result can be achieved with a 4L80 and some controller programming.
I opted for the 700R4 since I got the core and the T case for next to nothing and because this combo does neither require any exotic/expensive parts nor any modifications to the driveshafts. We will see how long it lasts.

I still have the original drive train as a backup and the neighbor who helped me with the installation on his lift offered me another 700R4/NP241 for less than scrap value. He is a professional auto mechanic and was somewhat impressed when I drove off his property, pushed by the first automatic transmission I ever rebuilt in my life.

When I first looked at the disassembled valve body I was doubting my sanity of choosing a DIY rebuild but the guts of the 700R4 turned out to be fairly straight forward. Many thanks go out to Earl at Bozeman Transmission for his advice on what to change and how to set up the friction packs, him lending me the needed tools over weekends, and for double checking some of the critical tolerances.

PS: Before going on the longer trip I changed the fluid lines to the radiator so that the fluid returns to the transmission from the (cooler) bottom of the heat exchanger. This seems saner in the current 80 F weather than the original routing where hot (185 F) oil returns from the top of the radiator to the transmission. Next step is a temperature gauge and then possibly an auxiliary cooler with thermostat valve at the transmission if needed. I did the test drive today with a transmission pressure gauge hooked up to catch any anomalies early.

Nice. I need the 4L80e in my 1031 since it is quite gravitationally gifted at 8700 pounds with all my tools. Trying to do 65 leads to overheating. The OD will drop the engine speed to 2000 rpm, meaning less heat to the coolant and more to motivating.

For the record, the brake specific fuel consumption rises to 0.46 pounds of diesel per horsepower hour at 3600 RPM. At 2000, its only 0.42 .These are max fuel rates but the efficiencies are similar at partial furling.

Hey Alpine, did the same thing with mine. I'd like to pick your brain on the lockup you did so I can do the same. Also on the list is the temp gauge. I have a gauge but that's about as far as I've gotten with that. Also, about re routing the oil coolant lines, I'll need to check in to what you are doing there as well as I really have no idea if I'm running mine too hard and hot or not. Also, I've found that the cable that kicks the gear down WOT, seems to allow first gear to go to redline if you aren't careful. Anything less and it won't kick down in any other gear. I'm not sure what my gears are either.

Keith_J said:

Nice. I need the 4L80e in my 1031 since it is quite gravitationally gifted at 8700 pounds with all my tools. Trying to do 65 leads to overheating. The OD will drop the engine speed to 2000 rpm, meaning less heat to the coolant and more to motivating.

For the record, the brake specific fuel consumption rises to 0.46 pounds of diesel per horsepower hour at 3600 RPM. At 2000, its only 0.42 .These are max fuel rates but the efficiencies are similar at partial furling.

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FWIW.........

Consider a 4L85E transmission, they where in Chevrolet Avalanche, GMC Savana, Chevy Suburban, and GMC Yukon. Rated a little heaver that the 4L80E. The 4L85E can handle 460 lb-ft of torque, which is slightly higher than what the 4L80E can handle.

Regards

Joseph

I too have a 700r4 and love it, much better on the road and with the 4.56 gears it chirps the tires going into 2nd and sometimes even 3rd.
I've done this with a couple of trucks and have had one problem and that might be because of all the salt up here in NY, I didn't realize what was happening until the second truck I did and was talking to my son and he had the same problem. The two top bolt holes are the biggest part of the problem, they eventually pull out and allow the transfer case to sag and leak ATF all over. The in the vehicle cure is to lift the Tcase back up and use longer bolts and as they screw all the way thru put a nut in the transmission side and then tighten the bolt and then lock down the nut. The two lower bolts go into blind holes so they need a thread sert and that means T-case removal.(only had to do that once) So check those two upper holes carefully before installation! It's a pain in the butt sitting on the side of the road low on ATF and trying to put it back in place in the dark.

nyoffroad said:

I too have a 700r4 and love it, much better on the road and with the 4.56 gears it chirps the tires going into 2nd and sometimes even 3rd.
I've done this with a couple of trucks and have had one problem and that might be because of all the salt up here in NY, I didn't realize what was happening until the second truck I did and was talking to my son and he had the same problem. What happens is the threads in the rear of the tranny case seem to get partially pulled out or stripped.
The two top bolt holes are the biggest part of the problem, they eventually pull out and allow the transfer case to sag and leak ATF all over. The in the vehicle cure is to lift the Tcase back up and use longer bolts and as they screw all the way thru put a nut in the transmission side and then tighten the bolt and then lock down the nut. The two lower bolts go into blind holes so they need a thread sert and that means T-case removal.(only had to do that once) So check those two upper holes carefully before installation! It's a pain in the butt sitting on the side of the road low on ATF and trying to put it back in place in the dark.

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I put Helicoil inserts in all four holes but using through bolts in the top holes is a good idea. I'll try to find Grade 8 bolts that have enough thread to fit a nut on the protruding part.

Just completed a 600 mile trip without any issues. Got 21 miles per gallon staying between 65 and 70 mph on the interstate. That is impressive for a full size, lifted truck with aerodynamics of a brick and a whole lot better than I ever got with the TH400 at any speed. Operating the engine near max torque rpm and locking the converter makes a huge difference.

Yup done a lot of these for customers with the cucv. Haven't had one complaint yet!

Iceman3005 said:

Yup done a lot of these for customers with the cucv. Haven't had one complaint yet!

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What axle ratios and tire diameters are you running in your CUCVs/Blazers?

Is there a way to get auto on/off lockup?

Ilikemtb999 said:

Is there a way to get auto on/off lockup?

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There are several ways to control TCC lockup automatically depending on the type of valve body you have. If you google "700R4 TCC lockup wiring" you will find an abundance of options.

However, keep in mind that a TCC can be fried even easier than the 3/4 clutches on the 700R4 if the engagement timing is off. This is the reason why I currently prefer the controller between my ears and a simple latching circuit for the TCC.

My TCC solenoid is engaged by pressing a button and disengaged by the brake pedal. There are some situations where I would like to momentarily override the disengagement and I may change the circuit accordingly.

I installed the 700R4 as an inexpensive and straight forward alternative to a stick shift conversion and never expected it to be as "smart" as more modern transmissions that are tightly integrated with the ECU.

There is a zone between manual and fully automatic where the technology does not have enough sensors and processing power to be truly convenient. The GM glow plug controller is another one of these examples. In the absence of a modern diesel ECU I prefer a simple push button.

4.56, with a 33 inch tire.

Ilikemtb999 said:

Is there a way to get auto on/off lockup?

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There are several options for the TC lock-up. I prefer the bowtie overdrive version. it locks up in 4th automatically, and it comes with a switch so you can lock it up in 2nd, or 3rd. Really helps when towing. There is a relay installed on the brake switch so when the brakes are applied it releases the lock-up.

alpine44 said:

There are several ways to control TCC lockup automatically depending on the type of valve body you have. If you google "700R4 TCC lockup wiring" you will find an abundance of options.

However, keep in mind that a TCC can be fried even easier than the 3/4 clutches on the 700R4 if the engagement timing is off. This is the reason why I currently prefer the controller between my ears and a simple latching circuit for the TCC.

My TCC solenoid is engaged by pressing a button and disengaged by the brake pedal. There are some situations where I would like to momentarily override the disengagement and I may change the circuit accordingly.

I installed the 700R4 as an inexpensive and straight forward alternative to a stick shift conversion and never expected it to be as "smart" as more modern transmissions that are tightly integrated with the ECU.

There is a zone between manual and fully automatic where the technology does not have enough sensors and processing power to be truly convenient. The GM glow plug controller is another one of these examples. In the absence of a modern diesel ECU I prefer a simple push button.

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The TC lock-up "timing" as you call it, is not true. TC lock up will not burn out the lock up clutch or the 3rd or 4th gear clutch packs. TC clutch burns out because of to much heat. 3rd and 4th gear burn out because of heat, towing in 4th gear, to much power for a stock trans.

The 700r4 is actually a very good trans and can compete with any modern trans, the 700r4 can be just as "smart" as a modern trans. Having the TV cable adjusted properly is all that is necessary to have it operate just as good if not better than any modern trans with all those stupid prone to fail electronic systems.

I have been building high performance 700r4's for many years. I have a customer that has a 1000 hp motor and hasn't broken it yet.

Iceman, Thanks for your encouraging comments regarding the 700R4. I know that I am a little over-cautious since this is the first automatic transmission I rebuilt and I do not want to spend another weekend day yanking out a burned up 700R4 and putting the TH400 back in my daily driver.

The fact that my transmission has gone the first 1000 miles with the oil looking as clear as new tells me that I did not make huge mistakes while building and adjusting this thing. What I do not know is what burned up the 3/4 clutches on the OEM core I got for cheap and what is behind all the 700R4 horror stories floating around on various forums.

I have read GM's bible on the 700R4 and several other reputable publications and fully understand the importance of the TV cable adjustment. To put it in simple terms, this cable tells the transmission what amount of torque is going to come from the engine and the TV valve adjusts pressures in the transmission so that the shifts occur at the right rpm and - more importantly - the clutch apply pressures are high enough to avoid excessive clutch slippage. (If the apply pressures would be always high, shifts would be to harsh at lower loads).

If the TV cable is too loose or the lever geometry on the IP or carburetor is wrong, the engine torque will get ahead of the clutch apply pressure, the clutches will slip excessively, and finally burn up from the resulting heat. Some folks may have missed that point but It is hard for me to believe that nobody who had issues with the TV cable did realize that something is very wrong with the way the tranny behaved and decided to stop right there. And after all the work rebuilding or even only installing the transmission, is it really so hard to hook up a pressure gauge and verify that the design parameters are met?

But regardless of what caused other transmissions to fail or what the true capabilities of my 700R4 are, I feel it cannot hurt longevity to have the TCC lockup occur during as little load as possible. What surprised me in the first days with the 700R4 is how much the torque converter slips under (nearly) full load. Now, I am anticipating the rpm drop with my foot while engaging the TCC clutch. What I meant with "timing" was to avoid TCC lockup during full throttle and resulting high rpm difference at the TCC plates. GM had a manifold vacuum switch in some of the gassers for that purpose.

I have not yet cut open a torque converter to see myself but the clutch in there is supposed to be even punier than the 3/4 packs. You are right about heat killing clutches but let's not forget that this means transmission temperature PLUS local heat from slippage. A clutch is supposed to slip until the rpm of both sides are matched, even under normal conditions. Trying to minimize the heat generated during clutch engagement by minimizing the speed difference and torque cannot hurt IMO.

I was going to call the converter manufacturer to find out whether the TCC is capable of handling repeated 3/4 and 4/3 shifts while locked. AFAIK, the GM wiring did never allow this but I like this mode for keeping things cool on long grades where my 4.10 axles and 34.5 tires are too tall for continuously staying in 4th. What is your take on that? (I can always manually unlock, down-shift and re-lock if that's better).

There are two more issues I need to fix on the valve body. Firstly, I may have gone overboard with the shims on the 1-2 accumulator and my 1/2 shift is currently a bit harsh. Transgo recommends curing the 2-4 band first by pushing in the 2-4 servo cover for a few seconds while the tranny is turning in 1st. Did you ever do this?

Secondly, my automatic 3/4 shift occurs way too early and is stacked under light "throttle"; I currently shift manually from D to OD to avoid this. I suspect a wrong spring in the 3/4 up-shift valve. With leadfoot applied, the 3/4 shift is fine so the 3/4 TV must be OK. I called Transgo to get the spring specs for verification that I used the right spring from their SK700 kit. Surprisingly, they would not release this engineering info but offered to troubleshoot the issue with me. We verified the line pressures which I knew to be OK. Now, I am waiting for better weather to tap the 2-4 servo cover so we can get a reading on the 4th apply pressure.(My case lacks the clutch pressure ports). Did you ever experience similar 3/4 issues?

I have not yet cut open a torque converter to see myself but the clutch in there is supposed to be even punier than the 3/4 packs. You are right about heat killing clutches but let's not forget that this means transmission temperature PLUS local heat from slippage. A clutch is supposed to slip until the rpm of both sides are matched, even under normal conditions. Trying to minimize the heat generated during clutch engagement by minimizing the speed difference and torque cannot hurt IMO.

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Yes I have had several torque convertors cut open, the clutch in there is pretty heavy duty. Well I should say it is heavy duty from the company I have make my torque convertors. As for slippage, the idea is to get the clutches to engage as quickly as possible to reduce the slip or even eliminate it, which in turn reduces heat. That is why a race trans will "bang" into each gear, obviously not ideal for a daily driver. But having it shift as quick as possible while keeping the "bang" as minimal as possible is what you should try for.

I was going to call the converter manufacturer to find out whether the TCC is capable of handling repeated 3/4 and 4/3 shifts while locked. AFAIK, the GM wiring did never allow this but I like this mode for keeping things cool on long grades where my 4.10 axles and 34.5 tires are too tall for continuously staying in 4th. What is your take on that? (I can always manually unlock, down-shift and re-lock if that's better).

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Yes you are correct in keeping the TC locked, a TC that is not locked is slipping (generating heat), of course it will need to be unlocked when stopped but once you hit 2nd gear locking it up will reduce heat. Keeping it locked when doing any 2/3, 3/4 or 4/3, 3/2 shift will not damage anything. I really like having the manual switch, that way I can tow in 3rd gear with the TC locked. It keeps the trans cooler, and reduces RPM's.

As for your gears, tires and 4th gear you should be fine, at 55 MPH your rpm's are 1550. That is a really good rpm for that speed. If you don't have a trans temp gauge then you may want to consider that as a next purchase. Use the governor port to get an accurate reading.

There are two more issues I need to fix on the valve body. Firstly, I may have gone overboard with the shims on the 1-2 accumulator and my 1/2 shift is currently a bit harsh. Transgo recommends curing the 2-4 band first by pushing in the 2-4 servo cover for a few seconds while the tranny is turning in 1st. Did you ever do this?

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Either remove some of the shims, or purchase the trans-go "bang shift" eliminator kit. It comes with several different springs to choose from that go into the valve body to stop that 1-2 bang shift.

Secondly, my automatic 3/4 shift occurs way too early and is stacked under light "throttle"; I currently shift manually from D to OD to avoid this. I suspect a wrong spring in the 3/4 up-shift valve. With leadfoot applied, the 3/4 shift is fine so the 3/4 TV must be OK. I called Transgo to get the spring specs for verification that I used the right spring from their SK700 kit. Surprisingly, they would not release this engineering info but offered to troubleshoot the issue with me. We verified the line pressures which I knew to be OK. Now, I am waiting for better weather to tap the 2-4 servo cover so we can get a reading on the 4th apply pressure.(My case lacks the clutch pressure ports). Did you ever experience similar 3/4 issues?

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An early 3-4 shift could be several things, one could be TV cable needs to come out 1 or 2 more clicks. Not only does the TV cable control line pressure, but it does play a small part in shift timing, vs throttle, vs governor. TV cable adjustments are a trial and error, move it one or two clicks then test drive, repeat until you get desired shift points. Also check the pressure every time you adjust TV cable to make sure it is within specs. There are several ways to increase TV cable pressure by installing heavier springs in the valve body. I highly recommend the heavier springs. Or could be your governor weights are incorrect causing to early of a 3-4 shift, this is also a trial and error, governor weights are a pain.

The accumulator spring only determines how quickly that shift will happen and how firm. A lighter spring will produce a slow and smooth shift (slipping), and a heavier one will produce a quick and firm shift (less slipping).

alpine44 said:

What axle ratios and tire diameters are you running in your CUCVs/Blazers?

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They are running the stock 4.56's some have the stock 32 inch tire, others are running 33's, 35's, even did one that had 37's.

My truck is running 305/70/16 33/11.5/16

I have only done one blazer cucv and he had the stock 3.08, with 33's. Was really lugging the engine in overdrive, but he seemed happy with it.