Cooked THIRD 700R-4 GM Suburban Transmission.

[59toaster]

I am trying to find confirmations but I swear I read the 4L60e and the 4L80e has a thermostat inside it that bypassed the AUX cooler till warm.

I'll keep looking tonight and see if I find a exploded veiw to verify

[Silvertwinkie]

You could be right....but when doing a full trans fluid purge on the 4L60e from a cold start (amb temp of about 60 outside), disconnecting the oil to air line to allow the fluid to be pumped out (while pouring fresh in the dipstick tube) means to me one of three things on my 4L60e....either that any type of thermostat may be broken to an open position, it goes to the oil/air at lower amb temps of about 60 degrees, or it doesn't have one. Not sure on the Burb yet...only has 6k on the trans...I figure in another few thousand, I'll put the Amsoil ATF in and find out.

[darryl97420]

After checking with the RPO code list I learned that my truck has the GU4 or 3.08 ratio. From what I understand this rearend was intended to improve fuel economy. With my 700R4 tranny and 3.08 gears I don't think I should be towing anything much less my Argosy 28.

How difficult is it to change out the gears to the 4.10?

[59toaster]

Originally Posted by darryl97420

After checking with the RPO code list I learned that my truck has the GU4 or 3.08 ratio. From what I understand this rearend was intended to improve fuel economy. With my 700R4 tranny and 3.08 gears I don't think I should be towing anything much less my Argosy 28.

How difficult is it to change out the gears to the 4.10?

About $180 for gears and $300 labor or a Junkyard axle with the gears you want.
Then change the drive gear in the transmission to get the speedometer acurate.

[overlander63]

Originally Posted by 59toaster

Then change the drive gear in the transmission to get the speedometer acurate.

The gears are color-coded (naturally I forget which color a 4.11 would use). You can get he correct gear from your friendly GM dealer, they are not expensive.

[uwe]

I had my 4L60E rebuild last month. It started slipping badly at the slightest hint of acceleration, coupled with a check engine light. It turned out that it was not cooked, not even the least bit. The fluid was nice and bright red.
The damn thing broke mechanically, literally. They showed me parts that came out of my transmission that just simply were broken and/or sheared off. No lack of lubrication evident. I did have them use certain aftermarket parts and a HD torque converter, on their recommendation.

[59toaster]

Originally Posted by uwe

I had my 4L60E rebuild last month. It started slipping badly at the slightest hint of acceleration, coupled with a check engine light. It turned out that it was not cooked, not even the least bit. The fluid was nice and bright red.
The damn thing broke mechanically, literally. They showed me parts that came out of my transmission that just simply were broken and/or sheared off. No lack of lubrication evident. I did have them use certain aftermarket parts and a HD torque converter, on their recommendation.

While trying to find info to see if there is actually a thermostat in the 4L60's (neverdid find out) I ran accross a LOT of info about them breaking parts like shells and sun gears.

Here is an example.

http://www.smokemup.com/tech/700r4.php

[uwe]

Originally Posted by 59toaster

While trying to find info to see if there is actually a thermostat in the 4L60's (neverdid find out) I ran accross a LOT of info about them breaking parts like shells and sun gears.

Here is an example.

http://www.smokemup.com/tech/700r4.php

Interesting article. Only I never raced the burb ( yet) or did nitrous on it ( yet).
Los Angeles traffic and stop and go for hours does it just as well.

[Silvertwinkie]

The 4L60e is prone to breaks such as described, or at least the 4L60e units built prior to 2000 or 2001. The car forums are loaded with folks where the darn thing just went kaput.

As for swapping gears I did it with the SS. I went from 2.93s to 3.73s. 3.08s are not bad if you are towing about 5000lbs. It is not as nice on the trans as say 3.73s, but heck I towed the 6300lb Safari with 2.93s at first and towed the Bambi (about 5000lbs) without any issues. Buying your gears from GM has gone up A LOT. When I did mine about a year and a half ago, they wanted nearly 2x what other places with darn near the same stuff wanted. This was a big increase compared to just months earlier. If you have ABS, you'll need the reluctor or whatever that ABS gear is in the diff as well. One thing about GM gears and vendors that have the same brand, GM takes the cream of the crop and if you have a good installer you won't hear the whine or vibrations, so even if GM is a bit more expensive, I would go with the GM brand. I have a slight whine in my rear diff. While you are in your diff upgrading the gears, I would either upgrade (if you don't have it) or replace the posi unit with an Eaton unit. Posi is just a great thing to have in a truck, 4x4 or not.

As for the heat issue, I was in the burb today when I realized that although the engine was at 210 per the coolant temp gauge, and the PCM via a scan tool had the PCM read temp at 204 degrees for the coolant, the trans temp never left the lowest mark on the trans temp gauge of 100 degrees until I got on the expressway and took it up to about 80mphm then it budged slightly off the mark and was maybe 105 for the trans temp with the oil to water to air to trans setup. I'd be real interested if the 4L80e has a thermostat if you ever come across it toaster. It would help me plan what mods I would do first, deep pan diff cover, trans pan or other goodies.

[darryl97420]

Originally Posted by Silvertwinkie

As for swapping gears I did it with the SS. I went from 2.93s to 3.73s. 3.08s are not bad if you are towing about 5000lbs. It is not as nice on the trans as say 3.73s, but heck I towed the 6300lb Safari with 2.93s at first and towed the Bambi (about 5000lbs) without any issues.

So does that mean that I do not need to change out the 3.08 gears to 3.73 on my burban? The only thing I tow is my Argosy 28. I checked with my local shop and the estimate to swap from 3.08 to 3.73 with bearing kit is about $500. The shop gave me the impression that 3.73 gears woule be a great investment into my suburban and that I would be able to feel the difference while towing.

[Silvertwinkie]

It's a tough call, particularly if your Argosy is less than 6000lbs. If your coach is less than 6000lbs wet, I'd be leaning toward not bothering, particularly if you don't tow in mountains or area of fair hills. If in fact you are close to or exceed 6000lbs, or plan on getting a coach that will exceed 6000lbs, and/or tow to the rockies or other lesser hill areas, then yea, I'd consider it and I'd also plan on replacing or upgrading to an Eaton posi rear end while it's apart, which would up the cost, but clearly be worth it. There I noticed a night and day difference between my factory Auburn posi and the Eaton 400# posi. Nothing in a car is an investment...it's just one big black hole money pit.

One question I have is the burb in it's current config having issue towing the Argosy where you currently go?

The one thing I can't tell is if you have a 1/2 ton or a 3/4 ton Burb. If it's a half ton and you are exceeding 6000lbs, then what might be a suggestion is look for a good used 3/4 ton. As one person said on this forum, you don't see many folks upgrading to a 1/2 ton.

[darryl97420]

Thanks for your response Silvertwinkie,

My burban is a 1/2 ton. According to the bouchure on my burban it is setp to tow 10,000 lbs. The GVW on my Arogsy 28 is 6200 lbs.

On my first trip out with the trailer we took it to Crater lake which included several steep climbs. While on the flat land and foothills I did leave the tranny in OD and burned it up. When the tranny was replaced I was told that I might want to beef up the rear end to 4:10 gears. That prompted me looking up what I had and what the burban was built for. Furthur reading told me that the 700R4 is not the greatest tranny on the road for towing but it's paid for and I expect to get abouy 50,000 miles out of it.

One thing I did not consider is that I am running 31x10.50R15 tires which might put a bit more stress on the running gear.

Here is the bottom line. I want to make sure that my little suburban will tow the Arogsy 28 3 or 4 times a year for our family trips. I already know that going down the highway it has worked out nicely but too many times I've read either here or on a Suburban owners group that the 700R4 tranny sucks and I shouldn't tow with the stock 3.08 gears. I keep hearing 4-part harmonies of "don't thow good money after bad" but I've already replaced the exaust from the cat back, had air rides installed in the rear, replaced the tow package wiring when the new brake controller was installed and soon here I'll be installing an oil cooler and a performance chip. After that a good paint job and I'll have practically a new tow rig.

[Silvertwinkie]

I hear ya. I have a calculator in Excel format. Might not be dead on with a 700R4 but it will give you a rough estimate on what your RPMs will be with various gears and tire sizes. PM me your email address and I'll send it to you....all you need is Excel to open it and play with it.

Looking at it right now, you may be *around* 2700rpm if you tow in 3rd w/ 3.73s. at 60mph and a bit over 3k w/ 4.10s @60mph. This thing says that you should be at about 2200rpms at 60mph with your 3.08s.

I don't pretend to know a lot about the 700R4, but if it's as bad as you've heard from folks who own them, then it's gonna be a bear no matter what gear, knowing that taller gears will be nicer to it and cheaper than another trans, but from what it sounds like, you towed in OD with it which could have been the issue.

[uwe]

For what it's worth, I tow between 5000-6000lbs with my 97 1/2 ton Suburban. It has 3:73 gear and the factory tow package. I run stock tires.
I so tow in 3rd, unless it becomes evident that 4th won't hunt the gears up and down. I have yet to have any power issues, not even crossing Wolf Creek pass at nose bleed altitutes, towing my 1971 fully packed TradeWind.
I could not imagine having taller gears than 3:73 in the rear axle, and that's with 28in tires.
31's and a 3:08 does not sound appealing to me. Looks like the gear change from 3:08 to 3:73 would make an otherwise marginal tow vehicle into a much friendlier one. Why not 4:10's? I'd say go for it.

[59toaster]

Originally Posted by darryl97420

Thanks for your response Silvertwinkie,

My burban is a 1/2 ton. According to the brochure on my burban it is setup to tow 10,000 lbs. The GVW on my Arogsy 28 is 6200 lbs.


One thing I did not consider is that I am running 31x10.50R15 tires which might put a bit more stress on the running gear.

.

I really HATE the way the automakers are not clear on towing capacities.

Those brochures are very misleading. The towing capacity of the 1/2 ton is "UP TO" 10k with the correct gearing. My 454 TH400 3.73 burb is rated 10k. If it had 4.10 it would be good for 12k.

With your set up I would refrain from pulling anything over 4k till you get some taller gears. 3.73 gears would be good to get you up to around 7-8k. 4.10 would get you to 10k on the gearing but if you have a 10bolt I wouldn't do it.

Towing package should include gears and it doesn't. Towing package is AUX cooler, and wiring for the most part. It doesn't mean it is set to pull 10k unless it has the proper gears and gearing is another option altogether.

[uwe]

Originally Posted by 59toaster

Towing package should include gears and it doesn't. Towing package is AUX cooler, and wiring for the most part. It doesn't mean it is set to pull 10k unless it has the proper gears and gearing is another option altogether.

My 1997 towing package included wiring, trans cooler, oil cooler, larger capacity radiator, increased alternator output, and the hitch. You're probably right, the gearing was not mentioned.
I feel comfortable recommending this vehicle for universal towing use up to 6000lbs. I am not even sure what it's rated at. Maybe 6700lbs?
My truck also has the limited slip rear end option, and a rear sway bar on the build sheet. All in all a good useable package.
I don't know much about the older models. Looking at teh brochures can be indeed confusing and misleading.

[Craig T]

I'll add my experience with the 4l60E ('98 Tahoe, 5.7L, 3.73, factory tow package, stock wheel diameter). I cooked the tranny fluid towing a '13 fiberglass trailer that weighed 2000 lbs loaded. After a stop I took off in overdrive over rolling hills along the Columbia river. Tranny fluid sprayed out the overflow and all over the trailer. I thought I blew a line to the radiator.

Corrections that I have made:
Always drive in 3rd when towing.
Synthetic ATF
Derale deep pan with cooling tubes.
160 thermostat
B&M shift firmness selector

The first trip after the improvements was up to Tahoe from the Bay Area for the Vintage Vacations Rally. It was over 105 in Sacramento as we climbed the hill with AC, traffic ect. Tranny fluid topped out at 220 deg. I was expecting to see some discoloration in the fluid but it was perfect. The last time the fluid was 220 is was cooked (non synthetic).

Of the "improvements" I made I'd say driving in third and synthetic oil are the most important to preserving the tranny.

my .02

[Silvertwinkie]

You know before this forum, I towed my 17' runabout (2500lbs GVWR) in overdrive short hauls. When we got the Bambi, I did a lot of what Craig said, but I also reflashed the PCM on my '96 LT1/4L60e combo to lock the torque converter sooner than later and thus, I had a tow/haul on at all times and towed both Airstreams in overdrive, until it started to hunt out gears on hills, etc. When we got the Safari (gvwr of 6300lbs) I did the same thing and in near 100 degree temps never got over 200, closer to 195 actually. I've towed several thousand miles using overdrive on our 4L60e, but would not suggest it be done unless you have your PCM programming modified. Though the synthetic trans fluid will take the abuse of 220 degrees, the clutches and internals will not. The fluid will still look great, but in reality, the trans clutches were baking in the case and warping will start to happen at 220. Anything over 200 degrees is bad news....I think our 2004 burb even has a limp mode the factory installs in the program if the temp in the trans gets over about 205 degrees.

Your 98 350's OBD2 can also be flashed to make the TC lock sooner than later. I used www.pcmforless.com The guy knows his stuff.

[Silvertwinkie]

Originally Posted by 59toaster

I ran accross a LOT of info about them breaking parts like shells and sun gears.

Here is an example.

http://www.smokemup.com/tech/700r4.php

Here are a few more:

http://impalassforum.com/noncgi/ulti...=006666#000000

http://impalassforum.com/cgi-bin/ult...c;f=4;t=006509

http://impalassforum.com/cgi-bin/ult...c;f=4;t=006495

http://impalassforum.com/cgi-bin/ult...c;f=4;t=006061

There is a guy that goes by team tripp that does some bullet proof 4L60e build that can make the 4L60e as strong or stronger than the 4L80e..for course, I'm sure it costs war bucks to do.