Thread: 700R4 swap

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So after spending $60 a weekend to drive my truck about 100 miles I have seriously considering an overdrive trans, the 700R4 stands out.

With a mild amount of research I have determined that my TH350 with 9" tailshaft will drop right out allowing a 700R4 to drop right in using the same driveshaft and yoke requiring only yo move the cross member, no big deal. My local shop will do the install for $300 flat.

So looking at candidate transmission vendors I am considering:1
1. B&M's 700R4 for $2000 complete
2. A 700 Raptor from PATC in Lousiana for $2400 complete and shipped
3. A custom built 700R4 from my local shop for $1800 installed

I am going with a 2000rpm stall converter, not sure whether I should go lockup or not, depends on the year trans I believe, but I am no expert.

Does anyone here have any experience or opinions to share with me? Thanks in advance!

try calling phoenix trans 1-800-shiftup. I think thats the phone no.

As I recall, you have a nicely warmed 350 with 3.42 gears in your truck. I don’t know what size tires your running, but for purposes of discussion, let’s use 275/60 15 (I’m running these on my ’71 pickup).

With the 3.42s and a stock TH350, your truck should be pretty good fuel wise, i.e., at 6000 RPM the “roughly calculated speeds” are 58MPH in low, 96MPH in second and 145MPH in third (approximately 24.33MPH p/1000 rpm)! This doesn’t take drag coefficients into play – but even still, that’ some fairly high gearing. I think your poor mileage may be due to too high a stall speed or slippage from a tired converter. If you have a 3,000RPM stall you’d need to be going almost 73MPH in third gear before the converter actually stops slipping so it may be that you’re slipping at freeway speeds.

With a 2000RPM converter – you’d be golden on the freeway as the converter would be fully engaged at 49MPH. This is why the newer cars all have multiple speed transmissions with overdrive to allow a very low stall speed (some as low as 1000-1200!) to allow say a Ford Expedition to cruse at 70MPH and only be turning 1800RPM.

Now – to your question

700R4 with 3.42:

1st gear, 3.06+3.42= 6.48
2nd gear, 1.63+3.42= 5.05
3rd gear, 1.00+3.42= 4.42
4th gear, 0.70+3.42= 4.12

Your current TH350:
1st gear, 2.74+3.43= 6.16
2nd gear, 1.57+3.42= 4.99
3rd gear, 1.00+3.42= 4.42

The 700R4 is going to give you more snap through the gears and you will have a bit of overdrive in 4th gear for cruising the freeway.

The TH350 is a stronger transmission from the factory but a 700R4 properly built will be more than adequate for your truck.

I’ve not personally used them – but I hear nothing but good about Bowtie Overdrives in Hesperia – probably worth the drive (yeah I know – another tank of gas) from your place to talk with them and get their inside story. Their prices are very reasonable and they just do GM transmissions.

http://www.bowtieoverdrives.com/index.shtml

Let us know what you decide.

Merry Christmas,
Glenn

Glenn

I think you need to multiply ratios---not add them-----

Jerry

You win the prize Jerry! It was a test- uhh would you believe??

The 3.42 is a multiplier. The 700R4 ratios look,like this:
1st gear, 3.06*3.42= 10.46
2nd gear, 1.63*3.42= 5.57
3rd gear, 1.00*3.42= 3.42
4th gear, 0.70*3.42= 2.39

Your current TH350:
1st gear, 2.74*3.42= 9.37
2nd gear, 1.57*3.42= 5.37
3rd gear, 1.00*3.42= 3.42

Much better - Thanks, Jerry!
Glenn

Go with the custom build from your local trans shop. They will do just as good a job as any of the highly advertized shops. The 700 is an excellent trans when adjusted properly. I've been running them for many years. Rear end gear in the 41 is 3.73

Get a tranny built locally so that IF you ever have a problem you can drive over and speak with them face to face. As for converter,go with lock up. Hughes makes a really good one that we have been running in a 54 chevy that has had no problems at all. Also look up Redneck Performance http://www.redneck-performance.com/ really good converters and alot cheaper. I have one in my 32.

you might ought to think about a unit from GM--factory rebuild and warrantee all over the country---or buy one from salvage yard and rebuild it

Well the deed is done, my new 700R4 is in my truck and I drove it home from the trans shop last night - feels great! WOW what a difference in performance and feel over the tired TH350 that I originally installed (which was free)

The completeness of the kit made the install super easy, the trans shop had ZERO mods to do, which they tell me is rare; they were actually delighted with how easy the install went, as was my wallet. The install kit supplied included both a pressure gauge and temp gauge, now to find a home on my dash for another gauge.

The 700 shift points were set up perfectly following the instructions from Bowtie Overdrives, and the TV cable setup is real nice. I skipped the install on the TV adapter plate cause the lokar-style TV cable supplied bolted right up to the Lokar SRK-4000 bracket I already had. I may tighten up the TV cable a bit as I got used to the super-firm shifts from the 350, but I will drive it for a while before doing anything. The upshifts are so smooth you almost don't know it shifted if you are not paying attention and she drops into overdrive and locks up around 50mph, give or take, via internal pressure switch that triggers going into 4th gear - real nice setup.

BO supplied me with a relay to unlock the converter that triggers off the brake switch so you don't stall under heavy braking, and since I am not running a mechanical brake switch a bosch relay was supplied to be installed inline off my brake light switch, otherwise they supply a gm cruise control/brake switch to do the job - BTW this is a warranty point for them so the lockup safety switch must be installed.

Along with the new trans I got a new, higher stall torque converter. I opted to go with a 2000-2200 rpm stall, which gives a firmer, higher rpm launch over the stock converter I previously had; another nice plus to get my engine into it's RPM band before engaging. Another plus my driveshaft fit exactly without modification, so besides having to relocate my trans cross member, it was really an easy install.

If anyone was considering upgrading to a 700R4 or OD trans, all I can say is start saving your pennies. Sure I could have gone to a boneyard and pulled one, had it rebuilt, sourced all the install materials and hoped for the best, but for $2224 installed I don't think I could have done better myself. I really did research this aspect of the project for quite sometime so I really felt my efforts were well complimented by the quality of the components and instructions supplied by Bowtie Overdrives; dollar for dollar this was probably the single best upgrade (besides the motor) I put on this truck. In all reality, it feels like driving a modern vehicle now; except for the solid front axle.


As far as Bowtie Overdrives was concerned, +100 to them, great product, great support and great instructions/support - I recommend them 100% and would not hesitate to buy from them again.

Looks great - glad you had a good experience with Bowtie Overdrives. I have a 71' 1/2 ton that desperately needs this same fix. Will git with those guys in the spring.

Regards,
Glenn