4wd TH400 tranny options/problems dump truck - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cc_bob · 04-14-2006, 08:08 AM

Hello,
My 1986 4wd one ton dump with a TH400 has lost reverse, as a matter of fact in neutral in goes forward and reverse it seems like it is just fighting itself. Put it in park and it goes forward too (parking pawl was broke, I replaced it but the slots it is supposed to catch on are rounded off).

Is there any hope to get reverse going again for this tranny (without removing it)? The truck is used very little since it is for my own personal use, plow snow in winter and do a few errands(mulch, topsoil, gravel, etcl) in summer

If it is doomed, I have 2 other used trannies that I am considering due to budget and I can get them for a few favors once the truck is on the road again.

I can get a TH400 from a buddy out of a 2wd, but I do not know if a 2wd and 4wd have different output shafts? If they're the same, can I just unbolt the tailstock and bolt it to my xfer case?

The other tranny I can get is a TH350 that has a transfer case on it. My transfer case has a PTO on it that I need for my dump, so can I swap just the tranny? Or... can I possibly install my PTO in the other transfer case? Is the length the same? Any other changes needed?

Thanks for any advice you can give, I've changed lots of trannies but never had to mix and match before.

86k10 · 04-14-2006, 01:20 PM

Sounds like your forward clutch has welded the plates together, try puting it in neutral and hold your foot on the brake and stand on it, it may break loose and if it does you will find you have reverse but no forward gears.

cc_bob · 04-14-2006, 08:11 PM

Quote:

Originally Posted by 86k10

it may break loose and if it does you will find you have reverse but no forward gears.

Thanks for the info, sounds like it's time for a new tranny. Hopefully someone will know if I can use one of the other two.

Another thought is to rebuild the one in it. Can anyone recomend a good book on rebuilding one.

Thanks,

qksilver · 04-14-2006, 10:28 PM

identify the type of transfer case, that will tell if it can swap but the length is different than a 400. You will have to change output shafts so that the adapter will work on a 2wd 400

DrMaserati · 05-02-2006, 06:30 AM

Quote:

Originally Posted by cc_bob

Another thought is to rebuild the one in it. Can anyone recomend a good book on rebuilding one.

"How to Work With and Modify the Turbo Hydra-Matic 400 Transmission"
by Ron Sessions

Go to this site for great info on tranny rebuilding:
http://www.technicalvideos.com/video...smission.phtml

JP

04-14-2006, 08:08 AM	#1
cc_bob Registered User Join Date: Jan 2004 Location: Burton, Ohio Posts: 95	4wd TH400 tranny options/problems dump truck Hello, My 1986 4wd one ton dump with a TH400 has lost reverse, as a matter of fact in neutral in goes forward and reverse it seems like it is just fighting itself. Put it in park and it goes forward too (parking pawl was broke, I replaced it but the slots it is supposed to catch on are rounded off). Is there any hope to get reverse going again for this tranny (without removing it)? The truck is used very little since it is for my own personal use, plow snow in winter and do a few errands(mulch, topsoil, gravel, etcl) in summer If it is doomed, I have 2 other used trannies that I am considering due to budget and I can get them for a few favors once the truck is on the road again. I can get a TH400 from a buddy out of a 2wd, but I do not know if a 2wd and 4wd have different output shafts? If they're the same, can I just unbolt the tailstock and bolt it to my xfer case? The other tranny I can get is a TH350 that has a transfer case on it. My transfer case has a PTO on it that I need for my dump, so can I swap just the tranny? Or... can I possibly install my PTO in the other transfer case? Is the length the same? Any other changes needed? Thanks for any advice you can give, I've changed lots of trannies but never had to mix and match before. __________________ 67 C10 396 stepside project 72 C20 402 72 K10 SWB (plow truck) 86 K20

04-14-2006, 01:20 PM	#2
86k10 Registered User Join Date: Feb 2003 Location: Bertrand, Nebraska Posts: 355	Re: 4wd TH400 tranny options/problems dump truck Sounds like your forward clutch has welded the plates together, try puting it in neutral and hold your foot on the brake and stand on it, it may break loose and if it does you will find you have reverse but no forward gears. __________________ 98 Neon 97 Grand Prix GT 02 Grand Prix 40th Anniv. 86 GMC 5.0 77 Olds 98 6.6 REAL AMERICANS, DRIVE AMERICAN

04-14-2006, 10:28 PM	#4
qksilver Senior Member Join Date: Dec 2004 Location: Southern Pines NC Posts: 3,853	Re: 4wd TH400 tranny options/problems dump truck identify the type of transfer case, that will tell if it can swap but the length is different than a 400. You will have to change output shafts so that the adapter will work on a 2wd 400



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