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lefty
Dodge Dakota
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12/30/2003
00:17:41
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 Subject: towing problem
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in the past ive asked about my dodge but i have a question about my bronco and i hope you can help.
its a 87 351 35inch tires...when i hook up my trailer and i hit the gas the tires dont move,dont even spin in place? it has a big engine and i used to plow with it,what do you guys think?
Thanks for your time-lefty
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.boB
Dodge Dakota
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12/30/2003
14:42:21
| RE: towing problem
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Assuming that the vehicle is in sound mechanical condition. Sounds like your gearing is too high. Stock rear gears are somwhere around 3.00 or so. Addding larger diameter tires significantly decreases final drive ratio, which decrease the amount of torque applied to the pavement. Now you don't have enough torque to pull a trailer.
Try putting it in 4L for a short distance in a straight line. If it then pulls the trailer fairly easily, you need to change diff gears. Might as well add LSD while you're at it.
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Kowalski
Dodge Dakota
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12/30/2003
15:42:28
| RE: towing problem
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What transmission ? If manual, maybe your clutch is slipping.
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lefty
Dodge Dakota
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12/30/2003
19:03:51
| RE: towing problem
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its a automatic,and im going to try the 4lo thanks for the advice i'll let you know what happens.
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lefty
Dodge Dakota
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12/31/2003
08:29:02
| RE: towing problem
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OK i messed up a little. when im in 2wd the wheel wont spin and itt wont move but when i put it in 4wd it has no problem? what do you think? thanks
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.boB
Dodge Dakota
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12/31/2003
10:58:21
| RE: towing problem
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If you're in 4Low and it tows fine, then you need to change your differential gears to something lower, like 3.55 or 3.73. If you tow a lot, consider 4.10.
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lefty
Dodge Dakota
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1/04/2004
18:20:42
| RE: towing problem
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Thanks i will look into changing the gears the only problem i might have is time how long would you say it would take to do the job with one other person and most of the right tools
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.boB
Dodge Dakota
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1/06/2004
10:04:37
| RE: towing problem
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Depends. A competent mechanic who has done it before can complete the job in a couple of hours. I'v never done it before, so it would probably take me two days and three trips to NAPA.
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STS
Dodge Dakota
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1/06/2004
16:16:23
| RE: towing problem
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Then you must have the old C6 3 speed. those 3 gear auto's just arnt worth a darn when towing anything because the 1st gear ratio is just to high. You might could get a aftermarket 4 speed auto. Somethink like the 4r70w tranny.
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lefty
Dodge Dakota
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1/10/2004
10:54:32
| RE: towing problem
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Thanks guys,very helpful,i think it is the 3 speed
this is gonna be a pain in the ass considering its -4 outside
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.boB
Dodge Dakota
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1/10/2004
13:17:34
| RE: towing problem
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Lefty, you're missing the point. Let the math do the talking here. You can't tow because you have a final drive ratio that is too short. The ability to move is dependent upon the amount of torque you can apply to the pavement. In your driveline there are 5 areas where torque is multiplied: Torque converter, first gear cluster, transfer case, differential, and tire diameter. Changing any one of them will change the entire equation. Look at the gear clusters on a 10 speed bicycle. The transfer case increases torque when in 4L by underdriving the driveshafts. That's why you can tow in 4L and not 2H. You lowered your FDR by around 20%.
Assuming you have a 3.00 rear gear (stock in many trucks of that vintage), and stock 31" tires, your FDR was pretty decent. Not great for towing, but a pretty good comprimise with a three speed.
Now you have taller tires which has reduced your FDR even further. Think of it as trying to move the same rock but with a shorter lever. You can do it, but it takes more power.
You need to restore that relationship between all of those parts to regain you torque application. The easiest is to simply change tire size; have one size for towing and one for general driving. Next would be to change the differential gears to something like 3.55 or 3.75. Which of course will raise you highway rpm's. The best would be to swap to a four speed auto and then lower the diff gears. The C3 and the AOD have almost the same first gear ratios. But OD would be nice for highway driving.
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lefty
Dodge Dakota
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1/10/2004
19:16:13
| RE: towing problem
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DAMN!! bob where did that come from thanks for explaining it a little better for me.sounds like you know your stuff
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.boB
Dodge Dakota
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1/10/2004
23:52:16
| RE: towing problem
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Well, you're welcome. Sometimes I'm not good at getting my thoughts out the ends of my fingers in an understandable form. I'm glad I managed to make it clear.
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Kowalski
Dodge Dakota
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1/11/2004
09:18:39
| RE: towing problem
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Of course, an automatic transmission could be slipping too. It would be a shame to change the gearing just to find out the tranny was the problem - better make sure you eliminate that possibility.
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