Torn on proper gearing

[mduenas]

I put a 700R4 in my truck about 5 years ago from Bowtie. I already rebuilt it last year, so it only lasted 4 years. I have a feeling this is due to my gearing.

I have a 2.5 inch lift, running 33’s, Dana 20, 700R4 w/ overdrive transmission, and stock 3.50 gears, 9 inch rear.

I’m very sluggish with little power and have gone Over my 302 a million times, it is running great.

I am thinking of putting 4.11 in the truck, is this the proper gearing? Will it make a difference?

Is it something I can handle at home? Do I need special tools? I’m being quoted $4,000-$5,000 for a shop and I can’t justify that.

I was going to get gearing from wild horses, unless you know a better place, the WH 9inch kit.

Is there a great DIY thread I wasn’t finding on how to do the gearing?

 

[phred]

You will need some special tools. Dial indicator, inch pound torque wrench, hydraulic press are the main ones that come to mind. The 9” is fairly simple but it takes some time. The D44 will often require a case spreader to remove the carrier and gears. It’s more problematic to set up than a 9”. I would recommend having this done by a reputable shop unless you just want to learn but it will involve time. Tons of YouTube videos.

 

[Master Chief]

If you stay on road (no 4x4), you can just do the rear until you are confident that is the gearing that you really want. I had mismatched gears for three years.

I run 33x12.50-15 with a well built C4 behind a 331. Installed a 3.89 in the 9" during the restoration and drove it like that for two summers. It had good highway manners but was sluggish around the country roads so I swapped out the 3.89 to 4.11 and am very happy with it. I changed the D44 from the stock 3.50 to match the 4.11 rear the following winter.

 

[Broncobowsher]

Yes, the 3.50 gears were not nice to the transmission. 4.11s are a good step in the right direction. But I would go a touch more. Normally I would call 4.56 to 4.88s a good match for 33s and an overdrive transmission. The 700R4 has a lower 1st gear and not as much overdrive. That has me backing off just a little bit. 4.30/4.27 is probably my pick but would not pass on 4.56 if heavy, lots of high altitude, motor built a little more high strung, or ever planning on stepping up a size in tires. The 4.11s might be fine if you had a 351 with the extra grunt down low.

 

[jamesroney]

I put a 700R4 in my truck about 5 years ago from Bowtie. I already rebuilt it last year, so it only lasted 4 years. I have a feeling this is due to my gearing.

I have a 2.5 inch lift, running 33’s, Dana 20, 700R4 w/ overdrive transmission, and stock 3.50 gears, 9 inch rear.

I’m very sluggish with little power and have gone Over my 302 a million times, it is running great.

I am thinking of putting 4.11 in the truck, is this the proper gearing? Will it make a difference?

Is it something I can handle at home? Do I need special tools? I’m being quoted $4,000-$5,000 for a shop and I can’t justify that.

I was going to get gearing from wild horses, unless you know a better place, the WH 9inch kit.

Is there a great DIY thread I wasn’t finding on how to do the gearing?

Uhm...no. Yes, on the sluggish, but no on it lasting only 4 years.

The 700R4 was factory in the C-K truck and came with 3.08, 3.42 and 3.73 gears. Very uncommon to find 4.11 in a half ton. In either case, the Full sized blazer is bigger and heavier than your Bronco. No shortage of people running 33's on a half ton chevy. If your 700R4 quit, it wasn't because of the 3.50 gears.

I just swapped my Bronco from 3.50 to 4.11 last week. I think it cost me $650, and I ended up with an extra big bearing rear end. But I'm a cheapskate...

 

[Broncobowsher]

Mistake thinking a Bronco compares to a modern GM pickup in regards of drag and load. And no GM truck with a 700R4 ever came with 33" tires. The big boy tires of the day were 31x10:50R15s. And the 700R4 was never known for being robust either. Add in questionable use of overdrive and convertor lock up, or lack of. TV adjustment.

Drag takes HP to overcome it. Add some RPM and the torque loads drop to get the same HP. Torque is what is hard on transmissions.

Not to mention putting some proper gears will make it way more fun to drive.

 

[mduenas]

Thank you all for the replies! I do a lot of highway driving, but also drove from sea level to 6,000ft often. I do take it off roading, but definitely more highway and surface street than anything. I like the idea of trying the rear out first. And I’m going to call a few other shops to research pricing more. I don’t want to rip it apart and fail to get it together, or worse, destroy it myself.

 

[Yeller]

With a 700r4, 33’s and a 302 in my opinion 4:10-4:30 would be my go too as well. If you were running a 351 I’d run straight to 4:10’s.

You may find 4:10’s feel perfect, I have had the opportunity to test drive a lot of bronco’s, I feel a 302 needs to spin just a bit faster to have the right feel, and the reason for the 4:30 option.

As for the trans only lasting 4 years there are a lot of factors. Be certain line pressures are correct and measured with a gauge per Bowtie’s instructions, a little off and it’s ugly fast. Then there is the stuff just happens factor. As for the gear ratio ehh maybe, maybe not, millions of c/k trucks with 3.42’s and 32” tall tires. That being said, new gears will make a world of difference in drivability.

 

[jamesroney]

As for the trans only lasting 4 years there are a lot of factors. Be certain line pressures are correct and measured with a gauge per Bowtie’s instructions, a little off and it’s ugly fast. Then there is the stuff just happens factor. As for the gear ratio ehh maybe, maybe not, millions of c/k trucks with 3.42’s and 32” tall tires. That being said, new gears will make a world of difference in drivability.

This is the root cause of the problem. Plenty of c/k trucks with 3.07's and a 700R4 and 33's too. I'm not saying NOT to change gears...I'm saying that the transmission did not fail because you are running 3.50's and 33's. As @Broncobowsher says...it will be a lot more fun to drive with lower gears. But I'm not jumping into the "change your gears to have more fun" discussion. I'm in the "your 3.50 gears didn't cause your 700R4 to quit."

Automatic transmissions do not fail because you "lug" them, or because they start out a little steep. They fail because they get HOT. They may be more prone to overheat due to "lugging" them. But they are far more likely to overheat because of inadequate cooling. My 47RH behind my cummins never sees 3000 RPM. Plenty of Turbo 400's out there behind GM 6.5 Turbo Diesels that never see high RPM.

My advice to the OP is to put a temp gage in the automatic transmission. A well built 700R4 (call it a 4L60) is a good transmission.

 

[Yeller]

@jamesroney like usual we’re on the same page, we’ll said. Just getting there different ways.

3.42’s with factory 265/75-16’s (32x10.5) tires is really close to 33’s and 3:50. I personally run a 700r4 with 4.56’s and 37’s, been running the same unit since 2008, was also a transmission tech from 1990-1997 so I’ve built and installed a few 1000 700r4’s that I got warrantee if things went bad. Sometimes everything is right and stuff just happens.

One thing I didn’t ask, does it have a lockup converter? If it does and it was not functional that would be the root cause of failure, seen it time and time again. Bow tie builds them both ways. I've also listened to builders argue about that being necessary, unless it has been modified to work with a non lockup converter in my experience it will fail if it does not lock up while cruising.

 

[Qumanchew]

If you're not confident in doing the gear swap your self you could always buy a third member that already has the gears you want to try and swap it in. That is a job that doesn't require any special tools, well except a slide hammer to remove the shafts.

How many miles are on the trans? Discussing the longevity of mechanical parts in years of service doesn't usually help much. Miles or hours of use are much more help in diagnosing the actual problem. If you put on 100k miles in those 4 years there was no problem at all, if it was 4k then there was a bigger issue than your gearing.

 

[Broncobowsher]

...

One thing I didn’t ask, does it have a lockup converter? If it does and it was not functional that would be the root cause of failure, seen it time and time again. Bow tie builds them both ways. I've also listened to builders argue about that being necessary, unless it has been modified to work with a non lockup converter in my experience it will fail if it does not lock up while cruising.

That was where I was getting at with questionable use of overdrive, convertor lock up and TV setting. Overdrive too soon and leaving the convertor unlocked so it is drivable is very bad. TV adjustment needs to be matched to the torque produced. Factory calibration is for a torque/throttle pairing. If you produce more torque at a lower throttle setting (larger induction that allows more air to pass at less throttle opening) that upsets the calibration. This stuff is where I really hate old school transmission controls and favor modern computer as adjustments can be confined to a single gear/load and are not broad sweeping.