Lack of power & top speed

[jarednbonie]

I changed my tranny from a 700R4 to a TH400 w/ racing clutches and shift kit. I put a 5-6" lift and 35"s on it also. Now my top speed is 60-65 and I can't climb hills (6-7% grades) at more than 30mph. Does this sound normal for this engine and tranny? I know the TH400 came stock in lots of rigs, does any one have a stock rig w/ this engine and tranny? I have 170k miles on the motor, it sounds healthy and doesn't use oil. I'm not sure what's in the pumpkins, but the truck is an '87 1/2ton, the 6.2 was stock.

'87 Suburban, 6.2, 35"s

 

[Can Can]

I'm not sure why your highway speed had decreased- if anything, you should be able to go faster because of the increase in tire diameter.........HMMMMMMMM.........that's a bit confusing.

As for the loss of power, it sounds like you may have to regear in order to get back into the 6.2's power band. A lot of 6.2 1/2 tons came stock with 3.42s(including my 83), and if yours did, your 35s are causing you the problems. What size tires were originally on the truck?

Both problems could be tranny related, I guess. I don't know enough about TH400s to really comment though.............Other than the lack of power, how does the tranny work? It almost sounds like a torque converter problem........





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[jarednbonie]

I guess the tranny is ok. But I paid $1600 by the time it was all rebuilt w/ shift kit & racing clutches. And now it leaks fluid like I can't believe. I've had it back to the small shop 4x to get the pan gasket replaced but it won't stop leaking. Could there be a wrong torque converter or something? I'm thinking the guy that rebuilt the tranny might not have done a very good job (since it leaks and he can't fix it). Plus I think I over paid for the job, thinking I was getting a really good tranny and it would be worth it in the end.

'87 Suburban, 6.2, 35"s

 

[Can Can]

I hate to break it to you, but $1600 would have bought you a brand new bulletproof 700r4 from Jet. I paid $1100CDN(about $700 US) for a totally upgraded 700r4 WITH a shift kit. You payed WAY too much..........

. If I was you, I'd be kicking and screaming!!!!!!!!!! Any good tranny shop includes a new torque converter with any rebuild, but in your case, I'd be really suspicious.

Where are the tranny leaks coming from? How much fluid are you losing? If you're losing it from a leak at the pan gasket, it's not a huge deal. You could fix it yourself if you had too. But if the leak is coming from the front of the tranny or from around the fly wheel cover, I would suspect that your torque convertor seal is blown..........

My best advice to you is to take the truck to a few different tranny shops in your area and let them take a look and give you a WRITTEN diagnosis of the problem. Also tell them what parts were included in the rebuild and what you apid for the whole job. Based on what you find out, you can take it back to the guy that did your tranny and use it to get your money back. If the guy gives you any slack, report him to your local Better Business Bureau or Chamber of Commerce. Heck, for the $1600 you've invested I'd even consider getting a lawyer to send him a letter stating that the job wasn't done right and unless your money is refunded you'll be suing his ass...........

Keep us posted on any further developments. Whatever you do, make sure this guy doesn't get away with what he's done.



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[jarednbonie]

I have an appt at another tranny shop for next week, we'll see what we come up with (great more $ into this tranny). I know I over paid, I should have done more research first. My favorite is learning the hard way. I've already got a call into the Better Bus. Bureau.

I've had some people tell me I should just drop in a 454 and my worries are over. Plenty of power and my gears will be fine since the 454 has a much larger power band. I'm worried about the overall costs of a swap though. I've heard I might get about 10mpg with a 454 though, which actually wouldn't be that bad for my weekend driver. Any thoughts? I just don't want to pour money into gears and especially this engine if I'm going to end up wishing for a gas engine....

Thanks for the advice!

'87 Suburban, 6.2, 35"s

 

[desertrat67]

Re: Lack of power & top speed

I found out that the BBB doesn't really do anything to a businessthat has complaints called in on it.

 

[Guest66]

Re: Lack of power & top speed

I have a 6.2 w/ 700 tranny with a 4" inch in front 3" in back suspenesion w/ 33x12.5 mudterrains and my truck tops out at about 80-85mph